OBDII Mt conversion???

[TomsSVX]

I have heard that OBDII cars have issues with being converted to a standard shift. Has any one else heard of this? And why is it?? I would really like to try it myself and I would be willing to cut a pretty good deal on the first person who wants it done... More or less it would be feeding my curiosity

Tom

[svxcess]

...and I would be willing to cut a pretty good deal on the first person who wants it done... More or less it would be feeding my curiosity


You're really tempting me with that one. I was just talking to Dayle this morning about getting leather to match our beige interiors in case I wanted to fabricate a matching shift boot for a manual tranny swap.

But this is my daily driver and I need to get around.

I don't know why it couldn't be made to work.
>

[TomsSVX]

I have heard that the CEL will pick up the lack of a TCU... But I am not sure anyone confirmed this... If so, I would like to come up with a fix for the problem. Just throwing around the idea because I do not think there is a single OBDII mt SVX out there right now

Tom

[Chiketkd]

Tom,

I think the biggest stumbling block has been the lack of an ECU pinout diagram for an OBDII SVX. That stopped me from switching to a full stand-alone on my former '96. Get that, and I'm sure the swap can be done. :)

[gest24]

Hmmmm... I wonder what prompted this interest... lol

[TomsSVX]

i was really sparked by her and curiosity is gonna kill me... Just like that twin idea I have burning a hole in my head

Tom

[SoobCrazy]

Sorry to drag up an old thread, but has anyone successfully converted an OBDII car to a manual transmission?

[1986nate]

Sorry to drag up an old thread, but has anyone successfully converted an OBDII car to a manual transmission?

Sure, but not without a permanent CEL

[svxfiles]

Sure, but not without a permanent CEL

Really?:confused:
All the ones that I have done have been OBD1s.:o

[1986nate]

Really?:confused:
All the ones that I have done have been OBD1s.:o

Did a 97. 96 will as well due to the com link between the TCU and ECU.

[Huskymaniac]

One thing on my to do list is monitor that pin and see what the signal looks like. It is also the only thing keeping me from trying and OBD1 TCU in my 1996 to get the upgrades.

[Conn SVX]

What? You mean " The 1997 will as well , due to the com link between the TCU and the ECU. I had to read that 3 times

[TomsSVX]

Its a data line between tcu and ecu reporting the status of the tcu.... you will not be able to reproduce it

Tom

[Huskymaniac]

Its a data line between tcu and ecu reporting the status of the tcu.... you will not be able to reproduce it

Tom

You underestimate me.

[1986nate]

You underestimate me.

Good luck replicating everything the TCU would see and have it report back to the ECU. It's not a simple range of voltage but complete communication back and forth.

[SoobCrazy]

Damn, that is not what I wanted to hear guys! I was hoping all these years later that a fix would have been discovered.

I would like to come up with a fix for the problem. Just throwing around the idea because I do not think there is a single OBDII mt SVX out there right now

Still up for that challenge? I think my flex plate took a dump, so I'm begrudgingly collecting parts for a manual swap.

Tom, do you still sell modded pedal boxes and shift linkages?

[1986nate]

Damn, that is not what I wanted to hear guys! I was hoping all these years later that a fix would have been discovered.



Still up for that challenge? I think my flex plate took a dump, so I'm begrudgingly collecting parts for a manual swap.

Tom, do you still sell modded pedal boxes and shift linkages?

You realize that post was from 6 years ago. It is common knowledge now. Both him and I are telling you and anyone else that wants to keep asking, that it will have a permanent CEL from the lost comm link.

[SoobCrazy]

Doesn't do much good when the thread's topic doesn't have a resolution, now it does! :)

Would it be possible to take a freeze-frame or a few seconds worth of data from the TCU and send a loop of that data to the ECU to trick it into thinking that the car still has an automatic?

Would simply leaving the TCU plugged in and in place on the car be enough to get around this CEL business?

On a slightly related side note, has anyone ever converted an OBD2 car back to OBD1 ECU/wiring/TCU to get around these issues?

[icingdeath88]

Doesn't do much good when the thread's topic doesn't have a resolution, now it does! :)

Would it be possible to take a freeze-frame or a few seconds worth of data from the TCU and send a loop of that data to the ECU to trick it into thinking that the car still has an automatic?

Would simply leaving the TCU plugged in and in place on the car be enough to get around this CEL business?

On a slightly related side note, has anyone ever converted an OBD2 car back to OBD1 ECU/wiring/TCU to get around these issues?

There will be sensors and such that are missed by the TCU due to the lack of an auto transmission that will result in other errors.

Changing it to OBD1 wiring ought to work fine for getting rid of the CEL, but it wont' pass emissions testing or whatever due to the lack of OBD2. Actually, the thing to do would be to build an OBD2 - OBD1 adapter, then just plug in the OBD1 ECU. I think Young Tom made one, and I'd be up for the challenge if I had an OBD2 pinout.

[Huskymaniac]

Good luck replicating everything the TCU would see and have it report back to the ECU. It's not a simple range of voltage but complete communication back and forth.

Ok, so it is a digital signal. Have you seen it to know what is being communicated? First off, it is one line so it is likely one way data from the tcu to the ecu. Second, obd2 is not required to report tranny data so it is unlikely that there is a ton of information being passed. It is probably a simple "ok" signal or a signal reporting the obd2 error code.

[SoobCrazy]

First off, it is one line so it is likely one way data from the tcu to the ecu... It is probably a simple "ok" signal or a signal reporting the obd2 error code.

This is what I was hoping it was. It's not CANBUS or anything, we're talking 1996 here... Can't be that complicated, right? :D

A jumper to an OBD1 ECU would be great, then I could take advantage of all the upgrades.
1) Has this been successfully done before? How close were any stillborn projects to completion and what caused the demise?
2) What would be involved? Could a few signals be tricked and work like OEM, or...?
3) Is this a worthwhile endeavor, vs. an aftermarket EMS?

[TomsSVX]

Yes i made a jumper for obdii to obdi. Yes it works. Its worthwhile because you will need it to go along with a standalone ems anyway.

Tom

[icingdeath88]

Yes i made a jumper for obdii to obdi. Yes it works. Its worthwhile because you will need it to go along with a standalone ems anyway.

Tom

Where did you get the pinout for the OBD2 ECU? I haven't come across one yet as far as I can tell.

Also, did you use twisted/shielded wires for the crank/cam wires?

[TomsSVX]

I had it on my old mitchel on demand cd.... old school members will remember i did a fundraiser for the network with them... dont have them anymore tho

I did not use sheilding as it was prototype work... but twisting the wires will work fine. In all reality the wires are not long enough to require it

Tom

[icingdeath88]

I had it on my old mitchel on demand cd.... old school members will remember i did a fundraiser for the network with them... dont have them anymore tho

I did not use sheilding as it was prototype work... but twisting the wires will work fine. In all reality the wires are not long enough to require it

Tom

Ok, cool. I'll see what I can find.

[Huskymaniac]

Ok, cool. I'll see what I can find.

If you look back you will see that I broke down the wiring and pinout differences. They are minimal except for that damn diagnostic signal going to the OBD2 ECU. Wanna work on this together? When things calm down after Christmas I was hoping to tap into that diagnostic signal and record it.

[icingdeath88]

If you look back you will see that I broke down the wiring and pinout differences. They are minimal except for that damn diagnostic signal going to the OBD2 ECU. Wanna work on this together? When things calm down after Christmas I was hoping to tap into that diagnostic signal and record it.

Sure. Where did you post that?

Also, I have a 94 and 97, and you have a 96. That should represent all of the TCUs and ECUs. Can you take a pic of the TCU and ECU, where the plugs go, so we can verify the exact wiring of each of them?

I am thinking I can take the plugs from my spare body harness (or find new connectors) and a DIY BOB from here (http://www.diyautotune.com/catalog/diybob-breakout-adapter-nippondenso-76-pin-p-411.html) and make an adapter if someone needs one.

[TomsSVX]

I still have my old jumper if any of you are interested

Tom

[icingdeath88]

I still have my old jumper if any of you are interested

Tom

Sure. How much do you want for it?

[Huskymaniac]

I still have my old jumper if any of you are interested

Tom

Is it a jumper for OBD2 ECU to OBD1 ECU or OBD2 TCU to OBD1 TCU?

[Huskymaniac]

Sure. Where did you post that?

Also, I have a 94 and 97, and you have a 96. That should represent all of the TCUs and ECUs. Can you take a pic of the TCU and ECU, where the plugs go, so we can verify the exact wiring of each of them?

I am thinking I can take the plugs from my spare body harness (or find new connectors) and a DIY BOB from here (http://www.diyautotune.com/catalog/diybob-breakout-adapter-nippondenso-76-pin-p-411.html) and make an adapter if someone needs one.

http://www.subaru-svx.net/forum/showpost.php?p=712457&postcount=19

[TomsSVX]

Is it a jumper for OBD2 ECU to OBD1 ECU or OBD2 TCU to OBD1 TCU?

Obdii to obdi engine ecm jumper.

Id take $75 for it

Tom

[icingdeath88]

Obdii to obdi engine ecm jumper.

Id take $75 for it

Tom

Sold. Still have the same paypal address?

[TomsSVX]

I do... ill dig it out of storage when i get a few mins

Tom

[icingdeath88]

K, lemme know.

[SoobCrazy]

Sold. Still have the same paypal address?

Drat... Any chance of a second run being produced?

[stiguy]

So what im understanding in this thread is that a obd2 svx cant have a MT without a cel on. Unless you use a obd2 to obd1 connecter. Is that correct? And if so would that still pass a emissions test?

I might be able to get a 96 but i wouldnt want to unless i can MT it with no cel as cali will fail you on a emission test if you have any cel on.

[Huskymaniac]

So what im understanding in this thread is that a obd2 svx cant have a MT without a cel on. Unless you use a obd2 to obd1 connecter. Is that correct? And if so would that still pass a emissions test?

I might be able to get a 96 but i wouldnt want to unless i can MT it with no cel as cali will fail you on a emission test if you have any cel on.

No. You would no longer have OBD2 communication so it would fail any inspection that would require hooking up an obd2 code reader.

[icingdeath88]

Drat... Any chance of a second run being produced?

I should be able to make more of them, if Tom's ok with that.

[SoobCrazy]

I should be able to make more of them, if Tom's ok with that.

If the price is good, I'm interested.

Honestly though, I would like to "trick" the OBD2 computer first and try to maintain my emissions comparability. While I would LOVE to have access to the ECUTune catalog with OBD1, that comes second to fixing my cracked flex plate.

Also, I'm holding out hope that someday, someone will release ECU re flashes for the OBD2 cars.

[icingdeath88]

Also, I'm holding out hope that someday, someone will release ECU re flashes for the OBD2 cars.

I'm working on that too actually, I need to pull the firmware from the ECU of my 97 and send it to LAN, and see if it can be flashed with the ECUtuner cable.

If I had to deal with the kind of inspection crap that you guys do, I'd just change the vin over to a 92 or something and call it done.

[Conn SVX]

Even that would be complicated. The vin # coincides with the odometer reading also. unless you found one vin #! With a little more miles or changed the dash Gage's < LOL> I think they would catch it. :mad::lol:

[1986nate]

Even that would be complicated. The vin # coincides with the odometer reading also. unless you found one vin #! With a little more miles or changed the dash Gage's < LOL> I think they would catch it. :mad::lol:

The cars are at minimum 15 years old. There are very few states that truly REQUIRE you to disclose the odometer on cars this old. In Wisconsin for instance, once a car is 10 years old, they are exempt from any odometer readings and even if you enter it, your new title will leave the spot blank.

[dragoontwo]

The cars are at minimum 15 years old. There are very few states that truly REQUIRE you to disclose the odometer on cars this old. In Wisconsin for instance, once a car is 10 years old, they are exempt from any odometer readings and even if you enter it, your new title will leave the spot blank.

Or places that actually check the odometer...

[Sean486]

The VIN is in multiple places on the car, and on the paperwork. How can you just change it to a 92?

[icingdeath88]

The VIN is in multiple places on the car, and on the paperwork. How can you just change it to a 92?

Find a 92 parts car, and switch them, basically. Or say, you have 2 cars, just switch them, and the plates. I think only the one on the dash and the one in the door jamb would need to be changed. If it matters that much for someone to go through the trouble, it's doable. People are lazy and don't pay too much attention to things like that.

[svxfiles]

Find a 92 parts car, and switch them, basically. Or say, you have 2 cars, just switch them, and the plates. I think only the one on the dash and the one in the door jamb would need to be changed. If it matters that much for someone to go through the trouble, it's doable. People are lazy and don't pay too much attention to things like that.

Switching of VIN plates is illegal,
or were you just kidding?

[92 SVX]

Let me check some info here, If you use the obd2 to obd1 jumper are you using both ecu's, so that obd2 diag would think the car (for emissions is correct?
Or would it be just using the obd1 ecu to keep the cel off?

but if emissions tried to connect to it would fail?

[Conn SVX]

In Conn they take the odometer reading and put it. In the computer when they do the test . If it was higher before they flag it as a turned back. They test all cars here back to 75 I believe.

[icingdeath88]

Let me check some info here, If you use the obd2 to obd1 jumper are you using both ecu's, so that obd2 diag would think the car (for emissions is correct?
Or would it be just using the obd1 ecu to keep the cel off?

but if emissions tried to connect to it would fail?

No, you'd be using an OBD1 ECU just to keep the CEL off for an MT swap, but you could also use the ECUtune stuff, and check codes without a scanner. And it would be easier to find an OBD1 ECU than an OBD2 one, if it needed replacing. It wouldn't really help pass inspection, because when they plug in the OBD2 scanner it won't be connected to the ECU.

Switching of VIN plates is illegal,
or were you just kidding?

I was, um, kidding? I would never do anything illegal, and neither should anyone else.

For the odometer issue, couldn't you just say the gauge cluster was replaced and is no longer accurate? (Hypothetically of course...) On the FL titles, there is an option for exactly that. Is that not a common thing?

[1986nate]

No, you'd be using an OBD1 ECU just to keep the CEL off for an MT swap, but you could also use the ECUtune stuff, and check codes without a scanner. And it would be easier to find an OBD1 ECU than an OBD2 one, if it needed replacing. It wouldn't really help pass inspection, because when they plug in the OBD2 scanner it won't be connected to the ECU.



I was, um, kidding? I would never do anything illegal, and neither should anyone else.

For the odometer issue, couldn't you just say the gauge cluster was replaced and is no longer accurate? (Hypothetically of course...) On the FL titles, there is an option for exactly that. Is that not a common thing?

Yes, also the DMV may issue a branded title but it's not like the car becomes unsellable should the time come. You would just have to disclose that there is a branded title for odometer rollback. Also, the fact still remains that while they may jot down the mileage, they still become exempt after a certain time frame. As I said, most states it's 20 years old or less. In PA, they will note the mileage for every inspection, however you can still put in as exempt for the title on anything 10 years or older as well.

[Tireiron]

I'm just finishing my 6MT swap on my 96 OBDII, but I'm also running Hydra so it wouldn't help you much with OBD functionality or check engine lights... Thankfully in MASS anything older than 15 years no longer gets plugged into the system during inspections.

[Huskymaniac]

I'm just finishing my 6MT swap on my 96 OBDII, but I'm also running Hydra so it wouldn't help you much with OBD functionality or check engine lights... Thankfully in MASS anything older than 15 years no longer gets plugged into the system during inspections.

10 years in PA...15 years in MA...25 years in the communist state of NY!!!!!!!

[TomsSVX]

K, lemme know.

Found it... so whenever you want it

Tom

[SoobCrazy]

This crossed my mind at work today: Does anyone know what code is specifically thrown in regards to the tcu on an obd2 swapped svx?

[icingdeath88]

Found it... so whenever you want it

Tom

Got it today, thanks.

[Huskymaniac]

Got it today, thanks.

How did that adapter work out for you ID? Do you know where the OBD1 lines go? Do they end up in the OBD2 connector? There are cables that adapt OBD2 readers to OBD1 connectors. I am looking into whether or not that could be used to satisfy emissions requirements.

[SoobCrazy]

Bump to this... I am started my conversion over the weekend. I didn't get a chance to sample the TCU to ECU signal for the OBD2, so I'm hoping someone else has been getting closer.

[Huskymaniac]

Bump to this... I am started my conversion over the weekend. I didn't get a chance to sample the TCU to ECU signal for the OBD2, so I'm hoping someone else has been getting closer.

I may give it a shot this weekend. Been too busy to think about going into that rat's nest while hanging upside down. I have a handheld scope here waiting to be used.

[SoobCrazy]

Oh please, please, please! I want to have a functioning cchek engine light.

[TomsSVX]

Its is a communication that is run by pulse width. It is intelligent and transmits more than just an "all clear". Duping it is not possible. The only way around it is to get someone to rewrite the stock engine ECU to not look for the TCU on the datalink

Tom

[SoobCrazy]

So is there a way we could leave the TCU in the car, run dummy signals to it, and allow the TCU/ECU link to remain intact?

[TomsSVX]

you could try, but the missing inputs from the trans will likely cause a CEL... but anything is possible

Tom

[SoobCrazy]

I'm working on that too actually, I need to pull the firmware from the ECU of my 97 and send it to LAN, and see if it can be flashed with the ECUtuner cable.

If I had to deal with the kind of inspection crap that you guys do, I'd just change the vin over to a 92 or something and call it done.

Any luck with this or in building another jumper harness for me?

[Huskymaniac]

Its is a communication that is run by pulse width. It is intelligent and transmits more than just an "all clear". Duping it is not possible. The only way around it is to get someone to rewrite the stock engine ECU to not look for the TCU on the datalink

Tom

Nothing is impossible. It may be unrealistically difficult but not impossible.

[TomsSVX]

Nevermind... its clearly out of your grasp as to what a datalink is and what it is used for... spend all of your free time trying to duplicate something you are not comprehending

Tom

[Huskymaniac]

Nevermind... its clearly out of your grasp as to what a datalink is and what it is used for... spend all of your free time trying to duplicate something you are not comprehending

Tom

I don't know which part of this is the funniest. And all that from saying nothing is impossible. Wow. Someone needs more fiber in their diet.

[SoobCrazy]

Nevermind... its clearly out of your grasp as to what a datalink is and what it is used for... spend all of your free time trying to duplicate something you are not comprehending

Tom

Please help me understand what type of signal this is. What is the TCU spitting out and what is the ECU expecting to see? I will be the first to admit that I am quite ignorant about the SVX, but it just doesn't seem like this is an impossible challenge.

You have said this is impossible at least three times in this thread, but I have not read WHY it is this way.

I'm not trying to be antagonistic, but you know why this is and I don't. Please educate me.

[TomsSVX]

Husky just wants the last word in any discussion which is typical for a child.

Im not saying i know what is broadcasted on the link... i just know what datalinls in cars are used for in more modern vehicles. They broadcast system status and can also broadcast parameter readings like tps. It may just be an all clear the tcm is putting out but more than likely the status request must be recieved from the engine ecu. Its a two way street.

Tom

[TomsSVX]

Not to mention unless you have access and knowledge of how to use an o scope, you cant see the signals.

Tom

[oab_au]

Not to mention unless you have access and knowledge of how to use an o scope, you cant see the signals.

Tom

That is the smart thing to do. The way I see it is the system links all the units so that only the ECU will report on all the units problems.
It calls all the units incluiding the TCU for a report on any codes, the TCU then sends back a reply on its condition. The signal that is used would be a data message.

So to find what is being sent, just check what is on the line with an oscilloscope when the key is first turned on, as that is when the ECU requests the reply.

I found that the 97 sends this signal at key on, and was catching the "Quick Change" charging up a filtering capacitor.

Harvey.

[svxfiles]

Not to mention unless you have access and knowledge of how to use an o scope, you cant see the signals.

Tom

Tom, I recently spoke to Husky and not only does he know how an oscillascope operates, he owns one.
Just sayin...
I think that the last time that I operated an osscillascope was in 1974, sigh...

[TomsSVX]

Tom, I recently spoke to Husky and not only does he know how an oscillascope operates, he owns one.
Just sayin...
I think that the last time that I operated an osscillascope was in 1974, sigh...

Great! why hasn't it been done yet?

Tom

[TomsSVX]

That is the smart thing to do. The way I see it is the system links all the units so that only the ECU will report on all the units problems.
It calls all the units incluiding the TCU for a report on any codes, the TCU then sends back a reply on its condition. The signal that is used would be a data message.

So to find what is being sent, just check what is on the line with an oscilloscope when the key is first turned on, as that is when the ECU requests the reply.

I found that the 97 sends this signal at key on, and was catching the "Quick Change" charging up a filtering capacitor.

Harvey.


Yes Key on is when the vehicle does an overall system readiness test. But system status is monitored throughout the ignition cycles and during "drive cycles" Drive cycles don't always have anything to do with key on but also relate to fuel used, heat cycles, hours running, and mileage. So it is an interactive process throughout the course of driving the vehicle.

In more modern vehicles you will find if an ecm is not programmed for the correct vin it will cause issue along the link. It is not something you can tamper with easily. Without all the manufacturers info about what is being broadcasted on the link, I find it "extremely unlikely" (not saying impossible in fear of a toddler's rage) that you will be able to reproduce any signal for the engine ECU to receive that will satisfy the communication.

Finding a good OBDII ECM writer who can take out the request from any TCM will likely be the best route

Tom

[Huskymaniac]

Great! why hasn't it been done yet?

Tom

Apparently it is because I don't want to waste my free time trying to duplicate something I can't comprehend. Seriously though, it is low on the priority list because I do have limited free time.

Feel free to PM me with whatever I said or did that annoyed you. I can't recall anything and, in fact, I think I have always treated you with the respect due to someone that is considered knowledgeable.

In full disclosure, I think I should reveal a few facts about myself since I did say your response above was funny. ( I admit that was obnoxious) I have an undergraduate degree in electrical engineering and a graduate degree in optical engineering. I attended MIT and the University of Rochester for graduate school. I have been using scopes since I was 13 and have been building electronics since I was 10. I am now 45. I have 22 years of experience as an engineer. I have worked on the Titan rocket, the hellraiser missle, the F22 stealth fighter, the joint strike fighter and classified spy planes along with sensors that have flown on NASA deep space missions, lasers that can cut your car in half, optical amplifiers that enable the internet to exist, detectors that can sense if you have been near an illegal drug in the past month as well as a mish mosh of other interesting gadgets. I have several patents and a bunch more in the works.

So I consider myself a pretty diverse and competent guy. However, a truly wise man knows that he knows nothing. I am well aware that I was never a gear head and didn't study a lot of mechanical engineering. So there is a lot I don't know about cars. But that list is getting smaller as it has become a hobby since I bought this car. Ironically, I am working on a new product right now that may end up in several high end cars. We have samples out to BMW, Ford, Peugeot, Chrysler, Jaguar and others.

I have a ton of respect for people with experience, skill and knowledge like OT, Nate a few others. I have the most respect for people that admit they may be wrong or lack complete knowledge of their subject versus those who refuse to accept those realities. The local guy I trust to work on my car when I don't feel I can do a good enough job on it or that I can do it fast enough is a really cranky old dude but we get along great. Why? Because I treat him the respect he is due and more. Actually, he reminds me of a really old Nate.;)

[Huskymaniac]

Yes Key on is when the vehicle does an overall system readiness test. But system status is monitored throughout the ignition cycles and during "drive cycles" Drive cycles don't always have anything to do with key on but also relate to fuel used, heat cycles, hours running, and mileage. So it is an interactive process throughout the course of driving the vehicle.

In more modern vehicles you will find if an ecm is not programmed for the correct vin it will cause issue along the link. It is not something you can tamper with easily. Without all the manufacturers info about what is being broadcasted on the link, I find it "extremely unlikely" (not saying impossible in fear of a toddler's rage) that you will be able to reproduce any signal for the engine ECU to receive that will satisfy the communication.

Finding a good OBDII ECM writer who can take out the request from any TCM will likely be the best route

Tom

From what I can tell from the pinouts and wiring diagrams, there is only one additional diagnostic line between the ECU and TCU on the OBD2 cars. It goes to pin 80 on the ECU and is labled "AT diagnosis input signal". It could be poorly named but, if it isn't, it implies that this is a one-way signal from the TCU to the ECU.

Is it possible that the early OBD2 cars which still had SSMI didn't have the ECU-TCU diagnostic signals that were required of later OBD2 cars? In other words, was there a transition period where not all of the inter-computer networking signals were standardized or yet required to meet a new standard?

[Huskymaniac]

Here is some data. I captured the data with the Fluke Scopemeter shown. The plot is of 13 sequential time frames overlaid on each other. As you can see, the signal is low speed and quite repetative. It wouldn't be difficult to make a small circuit that would replicate this signal. Someone with an OBD2 car with a 5 speed swap could inject this signal into the appropriate pin on the TCU connector (the one that leads to Pin 80 on the ECU) an see if the CEL stays away after being cleared.

http://www.subaru-svx.net/forum/attachment.php?attachmentid=17394&d=1376261828
http://www.subaru-svx.net/forum/attachment.php?attachmentid=17395&d=1376261846

[icingdeath88]

Here is some data. I captured the data with the Fluke Scopemeter shown. The plot is of 13 sequential time frames overlaid on each other. As you can see, the signal is low speed and quite repetative. It wouldn't be difficult to make a small circuit that would replicate this signal. Someone with an OBD2 car with a 5 speed swap could inject this signal into the appropriate pin on the TCU connector (the one that leads to Pin 80 on the ECU) an see if the CEL stays away after being cleared.

Ok, first, how would one go about "injecting" the signal into the ECU?

Second, do/can we know whether the signal that you read on the scope is enough to satisfy the ECU?

Let's keep the brainstorming going before momentum is lost.

[Huskymaniac]

Ok, first, how would one go about "injecting" the signal into the ECU?

Second, do/can we know whether the signal that you read on the scope is enough to satisfy the ECU?

Let's keep the brainstorming going before momentum is lost.

I will answer your question with a question. I don't have a 5 speed swapped SVX nor have I ever looked at a wiring diagram for a manual Subaru. Is there any form of TCU for a manual? If there isn't, does the TCU connector just hang there when a 5 speed swap is done? If so, Pin 80 on the OBD2 ECU is connected to Pin 11 of connector 55 on the TCU and the signal could be injected into this pin on the open connector. Our circuit would generate the pattern I showed over and over again and the output would be connected to pin 11 of connector 55.

I have also never had a TCU throw a code (knock on wood). When the OBD2 cars have a TCU code, does the ATF warning light still flash in addition to the CEL coming on? If so, does it still flash out sequences corresponding to various TCU codes?

[Tireiron]

On most other Subaru ECUs there is a pin that is either grounded or not to tell the ECU if it is a manual or auto setup, so they use the same ECU which of course saves in manufacturing costs. The 5MT cars do not have a TCU in them. This is based on the info from my 97 and 98 legacys and when i swapped auto to manual in the 98 using parts from the 97.

[oab_au]

I will answer your question with a question. I don't have a 5 speed swapped SVX nor have I ever looked at a wiring diagram for a manual Subaru. Is there any form of TCU for a manual? If there isn't, does the TCU connector just hang there when a 5 speed swap is done? If so, Pin 80 on the OBD2 ECU is connected to Pin 11 of connector 55 on the TCU and the signal could be injected into this pin on the open connector. Our circuit would generate the pattern I showed over and over again and the output would be connected to pin 11 of connector 55.

I have also never had a TCU throw a code (knock on wood). When the OBD2 cars have a TCU code, does the ATF warning light still flash in addition to the CEL coming on? If so, does it still flash out sequences corresponding to various TCU codes?

That scan of the signal could better if you used a V range of 0 to 50V and a faster time base, to make the signal more readable.
Our circuit would generate the pattern I showed over and over again and the output would be connected to pin 11 of connector 55

You can’t just keep sending that signal to the ECU. It will see it as a fault.

If that signal was taken, when the key is first turned on, then it consists of a ‘request’ and ‘reply’. You need to decipher it to see what part is the ECU’s request and what part is the TCU’s reply. You could do this by using a Data Logger to record the signal and put it in a graphic, as the TCU’s ‘all clear’ signal.
Then pull the front speed sensor, so that the TCU will report a fault to the ECU, log this signal, graphic it, and compare it with the ‘all clear’ signal to see which part is the ECU request and where the TCU reply starts.
As the first part will be the same, only the TCU's reply will change.
Once you have found the ‘all clear” reply, you can send it in, response to the ECU’s request.
This would probably need a Micro Chip, to look for the request and then send the ‘all clear’ response.

Harvey.

[Huskymaniac]

Do you know for a fact that this is a bi-directional line that operates as you say it does? Like I said earlier, the ECU pinout calls this line an "input" which implies it is one way. And the signal looks like it has a base frequency of 100Hz. That seems too low for a typical bi-directional data line. I was thinking it is more of a sequence like "data is coming", "start bit", "data", "stop bit". It could be even simpler. I have seen data links where a low speed signal is used to establish a connection and then it switches to higher baud rates. But that is not what this appears to be.

[oab_au]

If you look at what would happen. The ECU has to interrogate all the cars units, by request, they all can't just send their reports together. It has to be a bi-directional line.
The ECU calls all units in turn, and they reply.

Harvey.

[Huskymaniac]

If you look at what would happen. The ECU has to interrogate all the cars units, by request, they all can't just send their reports together. It has to be a bi-directional line.
The ECU calls all units in turn, and they reply.

Harvey.

I don't know why but I will respond to this. The line in question is only running between the TCU and ECU. It does not connect to the ABS, Cruise or climate control computers. Therefore, it does not need to be bi-directional. The SSM lines are the ones that network these OBD2 computers together and the SSM link is indeed bi-directional. Also, if the ECU only has one thing to say to the TCU, which is "what is your status?", and it wanted to know this status on a very regular basis, why would it need to say anything? All of the critical parameters for operation are sent on dedicated lines (MAF, TPS, RPM, the ALL IMPORTANT TORQUE CUT and others). The only thing missing from OBD1 TCUs is their ability to send error codes back to the ECU. So why not think it is possible that the TCU is only sending error codes over this line?

I think it would be helpful to present opinions and assumptions as such and facts as such so as not to confuse people and cloud the subject. Too many assumptions are framed as known facts.

[LetItSnow]

Is it not also possible that the ECU is sending a signal to the TCU, throwing a CEL if the connection is open (i.e., no TCU present)? It could be that something as simple as a resistor and either ground or static voltage would clean this up quickly.

EDIT: Regarding keeping the TCU in the car and connected to the ECU: <sl-i.net post (http://sl-i.net/FORUM/viewtopic.php?p=312620#p312620)> That may be worth something or nothing?

[oab_au]

I don't know why but I will respond to this.
:eek:
Well mate you have obversely got it all worked out and under control. So we should see you doing this soon.:rolleyes:

I'll leave you with it.
Harvey.

[Huskymaniac]

One other thing to consider is that this wouldn't just help OBD2 folks with a manual swap but it could also open the door for using OBD1 TCUs with OBD2 ECUs. A couple of other wires need to be swapped to make it work but, if it does, there would be no CEL and everyone could use LAN's TCU. That would be much better than the tranny destroying alternatives that are out there...clicking...like a time bomb.

[SoobCrazy]

Nice to see all the positive contributions, the brainstorming is great! I have two requests on data about the signal that may shed additional light on the TCU/ECU signal.

1) What happens when the car is being driven? Assuming the pics below were taken only at start-up and idle. WOT? Extreme vacuum, as in heavy braking? Or a presumed downshift, expected by TCU based on TPS change, etc.?

2) What signal would be sent if a trans sensor is unplugged (any distinct change in pattern frequency, wavelength duration)?

3)Can other circuits be plugged in here from existing pins on the harness for alternative purposes?

Can we see a few more combinations of ECU inputs? I know it may require a bit of work, but think of the poor OBD2 owners... :lol:

[LetItSnow]

It would also be interesting to see the signal with the torque converter locked vs unlocked and during shifting when the torque reduction thing would happen... if that's when it is?

[Huskymaniac]

I was pressed for time so I tried to grab something as quickly as possible. It is certainly possible to get a better connection and drive the car while capturing waveforms. I think it is also safe to disconnect the dropping resistor to generate a code so I can see what effect that has. But I won't drive the car with it like that. I will just see if the waveform is different at startup. I just don't know when I will be able to get to it. It is a PITA to get under there and the wiring is dense and difficult to manage.

If anyone has a manual swap in an OBD2 car and wants to try this out to get rid of the CEL, I am willing to program a chip with the waveform and hook it up.

Has anyone with an OBD2 car had the TCU throw a code? If so, can you tell me if the ATF temp light flashes like it does on the OBD1 cars to indicate there is a problem or does just the CEL come on?

[SoobCrazy]

Huskymaniac, I am working (slowly, due to fundage) on swapping a 5MT into my '96 and would be more than happy to try out your chip! Take your time with pulling those waveforms (within reason, 2013 would be nice, lol :lol:).

Let me know what you find in the meantime and if I can help in any way, shape or form!

[Huskymaniac]

Huskymaniac, I am working (slowly, due to fundage) on swapping a 5MT into my '96 and would be more than happy to try out your chip! Take your time with pulling those waveforms (within reason, 2013 would be nice, lol :lol:).

Let me know what you find in the meantime and if I can help in any way, shape or form!

I think I could whip something up quickly so let me know when you are ready for it. I may find time to monitor the waveform under more conditions but I REALLY hate hanging upside down and combing though those wires.

[Dispatch20]

I think I could whip something up quickly so let me know when you are ready for it. I may find time to monitor the waveform under more conditions but I REALLY hate hanging upside down and combing though those wires.

Bumping this topic from 5 years ago, as I'd like to add information relevant to the discussion. I've posted this on the SVX Facebook group but wanted to share it here, as well.

The OBDII TCU->ECM link is pretty simple, and not nearly as complex as others in this thread have speculated. Here are the basic facts:

The link is unidirectional from the TCU -> ECM. It appears to be a TTL-style push-pull signal (i.e. no pullup).
It is a single 5V digital signal that runs from the TCU to pin 80 of the ECM connector
It is a serial port stream but NOT a UART-style (e.g. COM port with standard baud rate and start/stop characters)
The bit rate is 10ms (very slow!) and repeats every 750ms. This means there are 75 characters (bits) in the repeating stream of data


I've observed 2 states with the use of a Digital oscilloscope as well as an Arduino computer setup to log the data stream. As noted above, there are 75 bits (10ms per bit) and they repeat indefinitely. The stream begins the second the key is in the ON position and continues after the ignition is started.

Here is a snapshot of the stream (a few traces of the signal are overlapped; I apologize!):
http://www.subaru-svx.net/forum/attachment.php?attachmentid=19893&stc=1&d=1563151747

Park/Neutral sequence: 11111111110000110010010010010010010010010010010010 0100100100100100100101100
Reverse/Drive/2/3 sequence: 11111111110000110010010010010010010010010010010010 0100100100100100100100101

Notice the small variation in the code above for being in Park vs Drive. Also notice that the pattern in both cases starts with 10 '1's followed by a '0'. We can use this to our advantage in data logging.

YouTube video of digital oscilloscope is here: https://www.youtube.com/watch?v=1zMiSCoyKzw

I've driven the car while logging the TCU datastream and observed that no change in pattern occurs during shifting, throttle, or steering changes. The same pattern occurs in 1st, 2nd, 3rd, and 4th gears.

Given the simplicity of this, it seems feasible to do a 5MT swap and emulate this OBD2 TCM serial port link. It doesn't seem like the ECM needs it for much. So how would this be done? I used an Arduino Uno to record the TCU stream with the OBD2 automatic tranny in operation. I can use the same Arduino to transmit the patterns noted above into the ECM. This should prevent the CEL light for code for 5MT swaps.

[Dispatch20]

In case you're curious and have some programming background, here is my Arduino C software for data logging the TCU data stream. To print out a nicely formatted line of data, I took advantage of the 10 repeating 1's followed by a '0' to synchronize my data capture. The hardware used is an Arduino Uno chinese clone that was $13 on Amazon.

I had to make a couple probe wires to stick in Pin 80 of the ECM and then into the Arduino digital connector pin #2.

Here is information on the ECM connector and a picture of my wire going into it. It's pretty easy to see and find but you need to be pretty flexible to stick your head under the dash.
http://www.subaru-svx.net/forum/attachment.php?attachmentid=19896&stc=1&d=1563152015
http://www.subaru-svx.net/forum/attachment.php?attachmentid=19895&stc=1&d=1563152007

You also need to create a common ground between the Arduino and the vehicle. I used some alligator clips on the cigarette lighter ground and then to a ground post on the Arduino. If you don't ground the car to the board nothing will work!

Here is a quick video of my prototype setup with the TCU wire, Arduino, and hacked together grounds: https://www.youtube.com/watch?v=F9ddmpcpLQs



Anyways, here is the Arduino software. And you can (hopefully) get the latest copy here: https://create.arduino.cc/editor/Dispatch20/3d423785-e16e-4449-8ae6-e52aca1e9984/preview

/*
OBDII SVX TCU Logger

Reads the 5V serial data stream output from Pin 80 of the OBDII TCU

The purpose is to record the TCU output stream and allow another piece of
software to recreate the stream when the TCU is absent. The primary use
is to allow a manual transmission swap without throwing a check engine light
for P1702.

*/

// Use Pin 2 of Uno board to receive the TCU output stream.
int TCU_Output = 2;

// the setup routine runs once when you press reset:
void setup() {
// initialize serial communication at 9600 bits per second:
Serial.begin(9600);
// make the pushbutton's pin an input:
pinMode(TCU_Output, INPUT_PULLUP);
}

void loop() {

int TCU_Val, Sync_Val = 0;

// Sync up to data stream
// O-scope showed a consistent 100ms of '1' followed by a '0' and the rest of the 750ms repeating sequence */
while(Sync_Val < 96) {
TCU_Val = digitalRead(TCU_Output);

if(TCU_Val == HIGH) {
Sync_Val++;
} else {
Sync_Val = 0;
Serial.println("Not Sync'd"); // This should only happen on startup if the Arduino starts logging after the car is turned on
}
delay(1); // 10x oversample for sync (e.g. 1ms sample rate on data that changes at 10ms)


// About 95 milliseconds have elapsed which gets us close to 100ms.
// The next 0 value after this will indicate the start of sequence.
if(Sync_Val == 95) {
Serial.println("Sync'd!!!!");
Sync_Val++; // Value of 96 will exit while loop
}
}

// Stall waiting for TCU to push a zero after the 100ms '1' sync sequence
// This should only be a few cycles (and you can let it print to serial to prove this)
while(digitalRead(TCU_Output) != LOW) {
//Serial.println("Stalled waiting for 0 after sync");
}

// Once the zero is lowered, we will expect a new bit every 10 ms
// So lets delay 5ms and sample at the middle of the data valid time (e.g. data is 10ms long, sample at midpoint)
delay(5);

// read and print out all 64 bits remaining (750ms - 100ms sync '1' - 10ms sync '0' = 640ms/10ms = 64 bits)
for(int i = 0; i < 65; i++) {
TCU_Val = digitalRead(TCU_Output);
if(TCU_Val == HIGH) {
Serial.print('1');
} else {
Serial.print('0');
}

delay(10); // 10ms bit rate.
}
// Print a newline then loop back to sync
Serial.println();

}

[irox]

Nice! Thanks for sharing. I was thinking about trying to do something similar (arduino to fake the TCU for a MT swap). Ultimately I didn't get an OBDII car, so won't have them problem. But still great to you do (and share!) this, nice to know I was thinking along the right lines.

Cheers!
Ian.

[SoCoNoHa]

Keep the TCU connected, and wire in some 10 watt 1.5k resistors as dummy loads for the solenoids, and a 330ohm resistor for the temp sensor. That's enough to get the TCU for an EZ30 to play nice, bet it works for the SVX as well.

[Dispatch20]

Keep the TCU connected, and wire in some 10 watt 1.5k resistors as dummy loads for the solenoids, and a 330ohm resistor for the temp sensor. That's enough to get the TCU for an EZ30 to play nice, bet it works for the SVX as well.
I bet that would work, too. Does anyone have the obd2 wiring diagram for the TCU?

[Dispatch20]

FYI - Here is the OBD2 ECU and TCU pinouts:http://www.alcyone.org.uk/ssm/obd2pinout.pdf

Anyways, I am trying to make the P1702 check engine light come on to see how and when it happens. I cut the signal from the ECU Pin 80 (AT diagnosis data waveform), and it didn't throw a check engine light. I drove around the block a couple of times and let the car warm up, and no CEL. I drove it around again today with it cut and still nothing. I actually went and disconnected the entire TCU harness (3 connectors worth) and drove the car around again. It drove fine around the block and still had no CEL.

Any ideas why the CEL isn't turning on for this? My OBD2 scanner had no current or pending codes. People clearly get the P1702 when they do 5MT swaps, so I wonder if it is a combination of factors that cause it to be thrown? And not just the one wire serial stream?

My plan was to

Cut the TCU<->ECU diagnosis signal and get CEL
Clear CEL code
Use Ardunio to transmit in the 750ms pattern I recorded during regular operation.
Hope that CEL does not go on with Arduino running
Do 5MT and use Arduino to keep the CEL off


Here is the cut wire with spade terminals for easy reconnection, and connection to an Arduino for logging the TCU, or emulating a TCU signal into the ECU:
http://www.subaru-svx.net/forum/attachment.php?attachmentid=19897&stc=1&d=1563745401

[Dispatch20]

Update: I previously had issues getting the CEL to go on for code 1702. I think the key is going on highway speeds for 10 minutes or more. Now that I can get the CEL to throw, I can test whether or not I can trick the ECM into thinking the TCM is in good shape.

Anyways, I put together a setup that can drive whatever signal it needs into the ECM.

I think the total cost should be below $50 to reproduce this:
Arduino Uno R3 clone - $12 (requires 5V-12 power, so you can't use the 14.4V from the car)
USB Type B 1.5" cable - $8
12V DC to 5V DC regulator - $12 (for powering Arduino via USB port)
Fuse Tap - $5

Here is what the TCM emulator setup looks like all connected together and ready for install:
http://www.subaru-svx.net/forum/attachment.php?attachmentid=19925&stc=1&d=1570402545

And I loaded the following code I wrote on the Arduino:
/*
OBDII SVX TCU Emulator

Transmits a sequence of serial bits to the ECU to prevent a check engine light
when the TCU is absent (e.g. manual transmission swap)

*/

// Use Pin 2 of Uno board to transmit the serial stream.
int TCU_Output = 2;

// the setup routine runs once when you press reset:
void setup() {
// Output pin for ECM input data stream
pinMode(TCU_Output, OUTPUT);
}

void loop() {

// The TCU outputs 75 bits at 10ms for a 750ms cycle time
// This sequence is what the TCU outputs when in Drive or Reverse
char data_drive[75] = "11111111110000110010010010010010010010010010010010 0100100100100100100100101";
// This sequence is what the TCU outputs when in Park or Neutral. May not need to use this.
char data_park[75] = "11111111110000110010010010010010010010010010010010 0100100100100100100101100";

// Print out the entire sequence
for(int i = 0; i < 75; i++) {
if(data_drive[i] == '1'){
digitalWrite(TCU_Output, HIGH);
} else {
digitalWrite(TCU_Output, LOW);
}

delay(10); // 10ms bit rate.
}

}


Here is what the fuse tap looks like. The 15A blue fuse is for the radio, and the gray fuse is a 2A one I am using for the 5V Regulator and Arduino.
http://www.subaru-svx.net/forum/attachment.php?attachmentid=19926&stc=1&d=1570403040

Here is the fuse tap inserted into the Radio fuse. This is one of the few fuses that has no power when the key is in the OFF position. You wouldn't want the Arduino powered up when the car is OFF! Also, you need to be careful with fuse taps. If you install it backwards it bypasses the fuse! Use a voltmeter to find the "hot" side of the fuse. You can see the orientation and location of the fusetap that I chose below. Also, note the metal nut at the very bottom of the picture; that is what I used to ground the regulator and Arduino.
http://www.subaru-svx.net/forum/attachment.php?attachmentid=19927&d=1570402533
Note: I had to Dremel the fuse tap skinnier so that it would fit into the fuse panel. I must have had the wrong size/shape fuse tap.

The fuse panel cover does fit over the installed fuse tap as long as I dremeled out a small portion near the latch.
http://www.subaru-svx.net/forum/attachment.php?attachmentid=19928&stc=1&d=1570403317

[Dispatch20]

So I installed the setup. I ran a wire (purple) from the Arduino up to the ECM, and powered it all up (black wire to fuse tap in fuse panel):
http://www.subaru-svx.net/forum/attachment.php?attachmentid=19930&stc=1&d=1570403954

I proceeded to take the car on a long cruise, and unfortunately I read out a "PENDING 1702" code, so something isn't correct yet. That's to be expected given this is such an experiment.

I must be missing something (or a few things). I'll need to do a full highway drive with the Arduino logging the TCM signal, and comparing that to what the Arduino is outputting.

I'll post back again when I learn any more about this. I realize this isn't a hot topic, but hopefully people find this interesting!

[Blacky]

It is interesting indeed. Don't be discouraged by the lack of activity on this site. It has gotten that way in the last couple of years.

[Sean486]

I think there are lots of people that would love to see this figured out.

[theflystyle]

Im not able to provide any useful commentary but I wanted to let you know this is a very interesting thread

[92 SVX]

I can tell you if there was a like button I and many others would have mashed it...

speaking of likes have you posted your findings on svx nation on facebook? I know currently that is the hotspot for svx activity.

[wdb]

Another "Like" button presser here. Keep us updated!

[Dispatch20]

I appreciate the support, guys! It does help motivate me knowing people are interested in this.

So after I posted last time, I set up the Arduino and laptop to do more data logging. I was suspecting that I might be missing some sort of TCU message that happens at highway speeds (or at some other period). Well, I did a 10 minute drive and the pattern did not change at all. It stayed exactly as I've always seen it. So then I cleared the CEL light, and drove another 10 minutes and there was no difference in the TCU pattern.

So anyways, I'm thinking that perhaps it is something simple like a grounding problem. The ECU has a number of different ground pins with different labels (refer to the OBD2 pinout link a few posts up). It would be very unsafe to assume all the different labeled grounds are all common with the chassis ground. So my next step is to wire the Arduino ground to the more specific ECU ground starting with the "control systems ground" on pins ECU 17/18). To be honest, I can just check with an ohmmeter to see how the grounds work, but I haven't yet. It's not the most convenient area (under the dash & steering wheel)

[Dispatch20]

Earlier this summer I bought the 1996 Service Manual OBD2 Supplement for $20 shipped on Ebay. I wanted to see what it said about the CEL P1702 code, and any debugging steps. See attached pics for the only 2 pages on this (although it also has the OBD2 updated wire diagrams which is always helpful).

Just like in my recent experience, it takes 2 trips to make the CEL go on. The 1st trip stores a "pending" 1702 code, and then the 2nd trip will turn on the CEL for the code. How the car defines a "trip" is interesting to me. It seems to follow the OBD2 drive cycle rules where the car must be below a certain temperature and then perform some level of driving before it will register the pending/actual 1702 code. I suspect this is why my brief drives around my neighborhood would never create a CEL code (even with the entire TCU disconnected).

The P1702 debugging steps in the tech manual just look for a short or open circuit. But they take the measurements relative to chassis ground, so I think my theory above probably won't help anything.

A second thought I have is that my Arduino starts outputting the signal in the ACCESSORY key position and the actual TCU outputs it in the ON position. I may be remembering this incorrectly, so I definitely need to double check that. I want to make sure that prematurely sending the pattern (i.e. in Accessory instead of On) isn't screwing something up here.

If I really can't get this method to work, then it's time to do a 5MT swap and try leaving the TCU installed and fooling it with load resistors (per the recommendation a few posts up). To be honest, I don't recall why people disconnect the TCU when doing a 5MT swap in the 1st place. Perhaps the ECU gets unhappy if the TCU sends the ECU a torque cut signal when it thinks it is shifting. Or maybe if the TCU doesn't sense proper A/B/C solenoids, it permanently causes a torque cut or some sort of limp mode. I don't think a code P1702 would be thrown, though. (Just capturing some random thoughts for now). FYI - I know people with 5MTs have sometimes had to override the torque cut signal into the ECU to prevent some stalling issues during shifting. Something about the torque cut signal disconnected/floating causing problems for the ECU.

Lastly - Yes, I do have a post on the SVX Nation Facebook page. It doesn't get a lot of interest, and I find this forum page an easier way to capture ideas, pictures, and links.

(One more thought - I should log what the TCU outputs in this ECU serial datastream when the tranny bulkhead harnesses are completely disconnected. I imagine this has to put out a different pattern than I've previously seen. If it doesn't, then what is the point of this new TCU serial data stream? I can speculate that it's required per OBD2 regulations to have the TCU->ECU signal but I really don't know. Subaru calls it a "diagnosis" signal. Since you can already talk directly to the TCU via SSM2 for diagnostics, I don't know what this new signal really does. Maybe it can capture freeze frame data in the ECU for certain tranny faults?)

[Dispatch20]

Quick update; sorry about all the text and no fun pictures!

I wired a ground wire from the ECU harness pin 17 direct to a ground pin on the Arduino. I think this might have actually helped! I took two long drives today (separated by 11 hours) and did not get a pending P1702 or CEL. I noticed that wiring this ground also made my datalogging Arduino setup work better. I want to test for a few more days before I claim success, though, but I'm feeling pretty good about it now.

I also datalogged and disconnected the large transmission harness by the starter to see what would happen. When you disconnect the big connector, the TCU just sends all '1's to the ECU which guarantees the P1702 will go on. The TCU must fail to see the right loads/solenoids/switches in the transmission and send the alert to the ECU via the pin 80 "diagnosis" signal. This lends credence to the theory that adding load resistors to the TCU could fool it into thinking it has a proper automatic installed despite having a 5MT swap.

Strangely, after filling up gas on the second half of my 2nd test drive today I got a pending 1101 Neutral Safety switch code. It seems unrelated to this testing but maybe some dirt got in the tranny harness when I plugged it back together, or maybe I didn't plug it all the way in. I'll keep an eye on that.

Lastly, the TCU does, in fact, start sending the serial data when the key enters the ON position (not Accessory). My Arduino starts sending data to the ECU when Accessory power comes on but it doesn't seem to matter. I also noticed that the power cuts out to Accessory devices when the starter is engaged, but it does NOT cut to the TCU. This doesn't seem to matter in terms of P1702, either.

[Sean486]

Quick update; sorry about all the text and no fun pictures!

I wired a ground wire from the ECU harness pin 17 direct to a ground pin on the Arduino. I think this might have actually helped! I took two long drives today (separated by 11 hours) and did not get a pending P1702 or CEL. I noticed that wiring this ground also made my datalogging Arduino setup work better. I want to test for a few more days before I claim success, though, but I'm feeling pretty good about it now.

I also datalogged and disconnected the large transmission harness by the starter to see what would happen. When you disconnect the big connector, the TCU just sends all '1's to the ECU which guarantees the P1702 will go on. The TCU must fail to see the right loads/solenoids/switches in the transmission and send the alert to the ECU via the pin 80 "diagnosis" signal. This lends credence to the theory that adding load resistors to the TCU could fool it into thinking it has a proper automatic installed despite having a 5MT swap.

Strangely, after filling up gas on the second half of my 2nd test drive today I got a pending 1101 Neutral Safety switch code. It seems unrelated to this testing but maybe some dirt got in the tranny harness when I plugged it back together, or maybe I didn't plug it all the way in. I'll keep an eye on that.

Lastly, the TCU does, in fact, start sending the serial data when the key enters the ON position (not Accessory). My Arduino starts sending data to the ECU when Accessory power comes on but it doesn't seem to matter. I also noticed that the power cuts out to Accessory devices when the starter is engaged, but it does NOT cut to the TCU. This doesn't seem to matter in terms of P1702, either.

Wow! This is awesome news. Hopefully, it doesn't come back.

[Dispatch20]

Update: I sent my prototype Arduino setup to someone in thr Facebook group with an OBD2 5MT. He has ran it for hundreds of miles and several days without getting a CEL.

The setup definitely works well enough to pass any sort of state inspection that checks for codes. Time will tell whether it is flawless or not. I hate to claim success without a ton of independent testing.

[irox]

That's awesome! Well done!

[theflystyle]

congrats!!!!

[Dispatch20]

Just checking back in to state that the prototype has been ran for a few months and many thousands of miles with no check engine light. That was a fun project! There isnt really a market for making and selling this thing, and only one person has even shown interest in replicating it. But it's good to know it can be done.

Looking back through this thread, I have to give kudos to HuskyManiac. He was the only one on the right track while a dozen others were naysayers.

Thanks for the support and recent kind words, everyone!

[svxnavyvet]

This is good work glad some one is following up on this.
Thank you
Just checking back in to state that the prototype has been ran for a few months and many thousands of miles with no check engine light. That was a fun project! There isnt really a market for making and selling this thing, and only one person has even shown interest in replicating it. But it's good to know it can be done.

Looking back through this thread, I have to give kudos to HuskyManiac. He was the only one on the right track while a dozen others were naysayers.

Thanks for the support and recent kind words, everyone!

[Huskymaniac]

Just checking back in to state that the prototype has been ran for a few months and many thousands of miles with no check engine light. That was a fun project! There isnt really a market for making and selling this thing, and only one person has even shown interest in replicating it. But it's good to know it can be done.

Looking back through this thread, I have to give kudos to HuskyManiac. He was the only one on the right track while a dozen others were naysayers.

Thanks for the support and recent kind words, everyone!

Ironically, I am getting a P1702 code! I never saw this post until now. Thanks for the Kudos. You finished what I started and did it exactly how I would have done it. Good work!

[Huskymaniac]

:eek:
Well mate you have obversely got it all worked out and under control. So we should see you doing this soon.:rolleyes:

I'll leave you with it.
Harvey.

Hey, mate, I noticed you never commented on the conclusion due to Dispatch's nice work. You still out there?

[Huskymaniac]

Without all the manufacturers info about what is being broadcasted on the link, I find it "extremely unlikely" (not saying impossible in fear of a toddler's rage) that you will be able to reproduce any signal for the engine ECU to receive that will satisfy the communication.

Tom

What's that now?

[Dispatch20]

What's that now?

:lol: Good to see you catching up on this! This was a fun project. I attached a picture of the final product.

[Dispatch20]

Ironically, I am getting a P1702 code! I never saw this post until now. Thanks for the Kudos. You finished what I started and did it exactly how I would have done it. Good work!

I saw a friend of yours posting for help on the Facebook forum a day or two ago. If you got a P1702 on an automatic SVX, my 1st guess is that you need a new TCU. I probably have a spare OBDII TCU if you want to try it out. I had a blown tranny in my 1996 that had TCU codes thrown but never a P1702 so I assumed the P1702 wasn't used to flag actual errors to the ECM.

I've only seen a P1702 thrown when the TCU harness is damaged, tranny is missing, or TCU is dead. But I learn new things every day.

[Huskymaniac]

I saw a friend of yours posting for help on the Facebook forum a day or two ago. If you got a P1702 on an automatic SVX, my 1st guess is that you need a new TCU. I probably have a spare OBDII TCU if you want to try it out. I had a blown tranny in my 1996 that had TCU codes thrown but never a P1702 so I assumed the P1702 wasn't used to flag actual errors to the ECM.

I've only seen a P1702 thrown when the TCU harness is damaged, tranny is missing, or TCU is dead. But I learn new things every day.

I tend to agree. It is probably a blown cap. Where in NY are you? Maybe I can swing by and pick up your TCU, if you still have it. I will pay you for it if it works.

[Dispatch20]

I tend to agree. It is probably a blown cap. Where in NY are you? Maybe I can swing by and pick up your TCU, if you still have it. I will pay you for it if it works.

I live in Syracuse so not too far from Corning. I'm not sure of you can drive your car this far up here, but we could try swapping the TCU right at my house.

[Huskymaniac]

I live in Syracuse so not too far from Corning. I'm not sure of you can drive your car this far up here, but we could try swapping the TCU right at my house.

I will PM you later today. I have a lot up in the air but that it a tempting offer. You must be young and skinny to be confident in being able to swap it out that easily.