swapping a auto for a 5spd on obdII

skuby98 · #1 04-22-2010, 11:56 AM

ok i am swaping the svx engine into a impreza with manual trans. my question is for OBDII and the auto trans.
does anyone know if the Check engine light with come on if there is no tcm, and if so does anyone know if i add a resistor to 1 of the 4 wires will act as a tcm, or does anyone have an idea? (no getting an svx is not an option)

James

TomsSVX · #2 04-22-2010, 05:01 PM

Im not sure how many more time you are going to ask but this is damn sure the last time I will tell you.... NO... **** NO.

The ECU and TCU communicate via a data link... "They speak to eachother in pulsewaves" No resistor or other hodgepodge crap is going to work.

Use an auto trans, reprogram the first OBDII ECU to stop looking for the TCU, or go suck eggs

Tom

redlinedeath · #3 04-24-2010, 07:34 AM

id listen to tom... only based on the fact that eggs are high in cholesterol... and we dont want that now do we?

TomsSVX · #4 04-25-2010, 10:38 AM

there are prob 4 threads from him asking the same thing... How many times do you need the same answer?

Tom

skuby98 · #5 04-25-2010, 10:59 AM

yea there is 4 or more threads, but until i can figure it out i am going to keep asking,
plus there isn't anyone to reprogram OBDII ecu's. i looked. i was told that the resistor might work.

james

TomsSVX · #6 04-25-2010, 11:05 AM

its a datalink, not a resistance check. Unless you can find out what frequency they chat at and design a control module to emit the proper pulse-waves when they are needed, it is not gonna happen... Just because you keep asking doesn't mean the answer you want is going to jump up and bite you in the ass.

Tom

1986nate · #7 04-25-2010, 02:30 PM

Quote:

Originally Posted by skuby98

yea there is 4 or more threads, but until i can figure it out i am going to keep asking,
plus there isn't anyone to reprogram OBDII ecu's. i looked. i was told that the resistor might work.

james

listen....

oab_au · #8 04-25-2010, 05:19 PM

As far as I know the ECU has the pressure sensor, and sends a varying voltage to the TCU, of 0 to 4/5volts. The TCU uses this voltage level, to use a shift map, that suits the altitude that the car is at.

If this is right, the ECU will only look at the line for an 'open or shorted' line. I think it can be satisfied by using a resistor on the ECU line, to ground, of about 3.9K. The ECU then just works this line OK, like it is the TCU that is on the end of the line.

I don't have the wiring diagram for the OBD11, so don't know that pin number it is.

I remember Phil said that this was the way the Altitude system worked, in his TCU thread, have a look there.

Harvey.

TomsSVX · #9 04-25-2010, 06:00 PM

That is OBDI system. The OBDII system needs a wavelength input from the TCU... I am not blowing smoke or deterring... Just simply that the OBDII system communicates through the ECM for the TCU for error codes and the like. It needs a datalink to do so

Tom

b3lha · #10 04-25-2010, 06:09 PM

Quote:

Originally Posted by oab_au

I remember Phil said that this was the way the Altitude system worked, in his TCU thread, have a look there.

That's how I think it works on the OBD1 units. But the OBD2 ECU and TCU are completely different. I would not assume that what might work on OBD1 will work on OBD2.

oab_au · #11 04-25-2010, 06:10 PM

Quote:

Originally Posted by TomsSVX

That is OBDI system. The OBDII system needs a wavelength input from the TCU... I am not blowing smoke or deterring... Just simply that the OBDII system communicates through the ECM for the TCU for error codes and the like. It needs a datalink to do so

Tom

Tom oh I see, in OBD11 does the ecu read the tcu trouble codes, the tcu doesn't act on its own? I have never seen the OBD11 wiring diag to see what it is. Do you have a scan of it?

Harvey.

oab_au · #12 04-25-2010, 06:17 PM

Quote:

Originally Posted by b3lha

That's how I think it works on the OBD1 units. But the OBD2 ECU and TCU are completely different. I would not assume that what might work on OBD1 will work on OBD2.

Thanks Phil,I knew the wiring colours to the OBD11 tcu are different to the OBD1, but as far as the connections for the QC are concerned, those are the same function.

To you have the wiring diag for the TCU?

Harvey.

skuby98 · #13 04-25-2010, 08:41 PM

i have them both for a 96. there is 4 wires that connect ecu to tcu. ecu pins are 80 (L), 79(LG), 64(Y), 47(LR). and on the tcu they are c11, c16, b5, b9. i have the scans from ALLDATA. (colors too).

james

b3lha · #14 04-26-2010, 02:10 AM

Harvey,

Just to point out what should be obvious to you.

If the ECU does throw a code because of the missing TCU. It's not going to be the pressure sensor that causes it. The pressure sensor is inside the ECU so it's not missing.

Phil.

TomsSVX · #15 04-26-2010, 05:14 AM

Quote:

Originally Posted by b3lha

Harvey,

Just to point out what should be obvious to you.

If the ECU does throw a code because of the missing TCU. It's not going to be the pressure sensor that causes it. The pressure sensor is inside the ECU so it's not missing.

Phil.

Actually the OBDII ECU uses an external sensor mounted on the R/S strut tower

Tom