A question for the Transmission experts

[oab_au]

Wrong post, bummer.

Harvey.

[oab_au]

Originally Posted by NiftySVX

I of course checked the tps voltage and at base it seemed normal. My TPS does have a slight dead spot in it. I pored over the repair manual last night and I think my problem may lie in the idle contacts in the TPS sensor, although I was not able to find a description of the specifications that would suit me. As I usually do during diagnosis like this I removed the TPS and manually moved it to try and and get it to raise line pressure, as I assume it would from my understanding of the way this system works. However, with the dropping resistor in place, rotating the tps sensor makes absolutely no difference in line. Interestingly, with the dropping resistor unplugged, (which raises base line to about 270) rotating the TPS sensor causes the line pressure to back down to 75 . This is what really confuses me, but It may be because I do not fully understand how line pressure is controlled by the combination of inputs, the manual doesn't really explain it.

I am going to outline assumptions and values which lead me to this diagnosis, based on the assumption that the following factors influence line control: Range Position, vehicle speed, engine load, and TPS (athough exactly how the TPS influences it is not clear, and what the idle contacts do for it)

Range position works because line raises to the higher spec in R.

Vehicle speed works because the speedo works, and that wouldn't effect line pressure at a stall test anyway

engine load has yet to be tested, it looks like this will require a pinout of the TCU

TPS is known faulty.

rotating the TPS sensor causes the line pressure to back down to 75 .
Does the pressure drop progressively with TPS movement or just switch down to the low pressure?

Range pressure boost for position for R is by the manual valve, not TCU.
There are no idle contacts in the TPS, closed is the 0.5V reading.
Engine load for the TCU is from the TPS.

If you have a multi meter that has % duty cycle on it, I would connect into the dropping resistor line to the A solenoid, to look at the signal to the A solenoid. 95% = full pressure, 5% lowest pressure. Signal comes from both the dropping line, and the Shift line from the TCU.

I don't think the trouble is in the box, I think it is electrical or TCU.

Harvey.

[longassname]

Did you perform the tests of the inhibitor switch listed on the 1st page of the pdf I posted? Since it's acting like it is in P or N it makes sense to think it thinks it's in P or N. Again you don't take the inhibitor switch off to test it. Half of what you are testing is it's installation/adjustment. Using the table from the PDF check the continuity of the pins at the harness connector for each selector lever position to make sure continuity exists between the correct pins and only the correct pins.

It couldn't hurt to throw in your stock TCU either. I wouldn't expect it to cause this but one never knows--might as well eliminate it.

Originally Posted by NiftySVX

I know it sounds like it's in P or N, but it's not. I am afraid to test it anymore because I don't think 75 is enough to hold the clutch together, but when the resistor is connected, and the tps is on the body, and the car is in D, 3, 2, 1, Line pressure is at 75 psi, while RPM is about 3000 and wheel speed is 0.

[NiftySVX]

I spent some time with the car this morning, and actually went through some diagnosis instead of poking around between customer jobs like I had been all week. I moved the TPS while the engine was running and finally got line to jump up to about 100. I then was able to rev the engine (in D) with the brakes locked down and line would start to come up, but then it would abruptly fall off back to 75 at a little over 5-10% throttle, and never come back up. I made a mistake by following the service manual's instructions for checking the TPS for resistance, but really I should have measured the voltage across the sweep. I'm not sure why I didn't do that in the first place. And after actually looking at the sensor diagrams in the manual it became obvious that it doesn't have idle contacts. I am still going to inspect the switch, and I am looking forward to my line pressure gauge that is gonna sit right below the radio.

[NiftySVX]

The TPS sensor did not fix the transmission. I am now going to attempt to read the duty ratio directly at the transmission connector for solenoid A.

Does anyone know anything about what it should look like as far as frequency? I don't have access to a select monitor so I can't read it in that form, but I do have a scope, and my fluke will read Hz.

[oab_au]

Originally Posted by NiftySVX

The TPS sensor did not fix the transmission. I am now going to attempt to read the duty ratio directly at the transmission connector for solenoid A.

Does anyone know anything about what it should look like as far as frequency? I don't have access to a select monitor so I can't read it in that form, but I do have a scope, and my fluke will read Hz.

The signal is a Duty cycle at about 60Hz. It is not the frequency, it's the Duty cycle that you need to see. Doesn't the Fluke have a % function with the frequency, my model 19 does.

If you are looking at the line to the A solenoid at the box on a scope, it will be a square wave, based on zero, rising to 3 volts, the input to the dropping resistor is a 12 volt signal. The length of the wave varies with the duty cycle. A 95% wave is low pressure a 5% wave is full line pressure.
Happy hunting.
Harvey.

[NiftySVX]

Originally Posted by oab_au

The signal is a Duty cycle at about 60Hz. It is not the frequency, it's the Duty cycle that you need to see. Doesn't the Fluke have a % function with the frequency, my model 19 does.

If you are looking at the line to the A solenoid at the box on a scope, it will be a square wave, based on zero, rising to 3 volts, the input to the dropping resistor is a 12 volt signal. The length of the wave varies with the duty cycle. A 5% wave is low pressure a 95% wave is full line pressure.

Happy hunting.
Harvey.

Right right, it does. For some reason I was thinking frequency, but that is what I meant. I suppose it would make sense for a duty % to be from 1 to 100. Ha. I'm starting to wonder if level 10 put the wrong kind of solenoid in the valve body. Surely it wouldn't plug in?

[Trevor]

Originally Posted by NiftySVX

Right right, it does. For some reason I was thinking frequency, but that is what I meant. I suppose it would make sense for a duty % to be from 1 to 100. Ha. I'm starting to wonder if level 10 put the wrong kind of solenoid in the valve body. Surely it wouldn't plug in?

Nate,

My answer to your enquiry by PM, should put you straight on the important issues. You are on a likely track through suspecting solenoid "A".

[NiftySVX]

I have tested all outputs of the TCU and found that they are all within specifications. Interestingly, when testing the output of the TCU, The green/red wire that goes to the dropping resistor outputs as specified, but it is not linear like the output of the green/yellow which goes directly to the solenoid. With about 14v at closed throttle, the green/red wire voltage decreases by several volts at about 10% throttle, which is the point at which line pressure will fall off with the resistor unplugged, which makes no sense to me.



I am going to repeat some facts I believe to be true in case I am in error.

The TCU outputs a voltage via the Green wire with a yellow tracer that connects directly to the solenoid according to the diagram. The TCU also outputs a different voltage on the Green with a red tracer that goes to the dropping resistor. The green/red wire terminates at the dropping resistor, while the green/yellow wire from the dropping resistor splices with the green/yellow that runs between the TCU and the connector at the transmission.

Now, when i have the resistor plugged in, I can measure the voltage at the transmission connector across the black ground wire and the green/yellow solenoid A wire. I get a reading that ranges from 2.16V to 2.14

The voltage at this point in the system should be some combination of the original signal outputted to the solenoid which is a 0-5V signal and the remainder of the 0-14v signal that was not dropped across the 12 ohm resistor.

So, If I have a voltage that varies from 0v at WOT to around 3 at fully closed on the green/yellow and a voltage that varies from 14v at fully closed to 0 at WOT on the green/red wire, I should have a combination of those two that results in a voltage that operates the 5 volt solenoid for more bleed down at low voltage to OFF at a full 5v as it is normally closed.

As this is my understanding of the system, I am unsure why I have a constant 2.15 volts at the connector for the transmission. If that voltage is supposed to range from 0 to near 5v as per my understanding of the system, then it would explain why my line pressure acts the way it does. It would tell me that the solenoid is working as designed, and maintaining a duty which corresponds to a value of 2.15 volts, say around 40%, which appears to have the effect of about 70 psi Line.

Am I in error somewhere? I am really frustrated with this.

However, I would like to confirm with someone that has a properly operating system. Who would be wiling to pull their trans conector by the starter and measure the voltage across the black wire and the Green/yellow? I would anticipate a drop to almost 0 volts at wide open as this should shut the solenoid off and allow max line pressure. If this is what happens on a properly operating car, then I will know that I have some kind of wiring issue between the TCU and the connector.

[oab_au]

Originally Posted by NiftySVX

I have tested all outputs of the TCU and found that they are all within specifications. Interestingly, when testing the output of the TCU, The green/red wire that goes to the dropping resistor outputs as specified, but it is not linear like the output of the green/yellow which goes directly to the solenoid. With about 14v at closed throttle, the green/red wire voltage decreases by several volts at about 10% throttle, which is the point at which line pressure will fall off with the resistor unplugged, which makes no sense to me.



I am going to repeat some facts I believe to be true in case I am in error.

The TCU outputs a voltage via the Green wire with a yellow tracer that connects directly to the solenoid according to the diagram. The TCU also outputs a different voltage on the Green with a red tracer that goes to the dropping resistor. The green/red wire terminates at the dropping resistor, while the green/yellow wire from the dropping resistor splices with the green/yellow that runs between the TCU and the connector at the transmission.

Now, when i have the resistor plugged in, I can measure the voltage at the transmission connector across the black ground wire and the green/yellow solenoid A wire. I get a reading that ranges from 2.16V to 2.14

The voltage at this point in the system should be some combination of the original signal outputted to the solenoid which is a 0-5V signal and the remainder of the 0-14v signal that was not dropped across the 12 ohm resistor.

So, If I have a voltage that varies from 0v at WOT to around 3 at fully closed on the green/yellow and a voltage that varies from 14v at fully closed to 0 at WOT on the green/red wire, I should have a combination of those two that results in a voltage that operates the 5 volt solenoid for more bleed down at low voltage to OFF at a full 5v as it is normally closed.

As this is my understanding of the system, I am unsure why I have a constant 2.15 volts at the connector for the transmission. If that voltage is supposed to range from 0 to near 5v as per my understanding of the system, then it would explain why my line pressure acts the way it does. It would tell me that the solenoid is working as designed, and maintaining a duty which corresponds to a value of 2.15 volts, say around 40%, which appears to have the effect of about 70 psi Line.

Am I in error somewhere? I am really frustrated with this.

However, I would like to confirm with someone that has a properly operating system. Who would be wiling to pull their trans conector by the starter and measure the voltage across the black wire and the Green/yellow? I would anticipate a drop to almost 0 volts at wide open as this should shut the solenoid off and allow max line pressure. If this is what happens on a properly operating car, then I will know that I have some kind of wiring issue between the TCU and the connector.

What you have said about the way the A solenoids connections are done, is right. This is a diagram of it.
.
The A solenoid is normally open, controlling a pilot pressure to control the pumps regulator pressure.

You won't find anything by looking at the voltage on these lines. The line to the dropping resistor will always be a 12 volt or 0 volt sig (depending on the battery voltage), the line to the A solenoid will always be 3 volt or 0 volt.
It is the Duty cycle that does vary. It is turned off to zero for 5% of the time, turned on to 3 volts for 95% of the time for a 95% signal.
It is not the voltage that varies, it is the current that flows during the on time, that varies the solenoids flow.
So it is not a combination of the two voltages, it is a combination of the 'on times' current that is controling the solenoid.

Harvey.

[NiftySVX]

Originally Posted by oab_au

What you have said about the way the A solenoids connections are done, is right. This is a diagram of it.
.
The A solenoid is normally open, controlling a pilot pressure to control the pumps regulator pressure.

You won't find anything by looking at the voltage on these lines. The line to the dropping resistor will always be a 12 volt or 0 volt sig (depending on the battery voltage), the line to the A solenoid will always be 3 volt or 0 volt.
It is the Duty cycle that does vary. It is turned off to zero for 5% of the time, turned on to 3 volts for 95% of the time for a 95% signal.
It is not the voltage that varies, it is the current that flows during the on time, that varies the solenoids flow.
So it is not a combination of the two voltages, it is a combination of the 'on times' current that is controling the solenoid.

Harvey.

So, you're saying the duty solenoid is operated by the current to the solenoid, not the voltage, which was my original theory before examining this circuit with a volt meter. If this is the case, then why do I observe a large voltage change at the green/yellow wire coming out of the TCU and one coming across the green/red wire to the resistor? and what circuit is in place between the two that regulates it to a constant voltage? Is this the purpose of the dropping resistor?

[Trevor]

It has been previously stated within this thread, that by way of practical experiment:-

“Unplugging the connector at the trans makes a constant 270 line. With the resistor in place, throttle opening makes no difference on line pressure. It won't leave 75 psi, even with the tps Removed and manually rotated.”


There is but one duty cycle adjusting line pressure via the direct circuit.

Solenoid valve “A” is normally closed. I have one in my hand.

A minimum of nine volts is required to open the valve against the included spring pressure and it closes at less than three volts.

Nate, Refer my second PM in reply to yours, for full and correct details.

[oab_au]

Originally Posted by NiftySVX

So, you're saying the duty solenoid is operated by the current to the solenoid, not the voltage, which was my original theory before examining this circuit with a volt meter. If this is the case, then why do I observe a large voltage change at the green/yellow wire coming out of the TCU and one coming across the green/red wire to the resistor? and what circuit is in place between the two that regulates it to a constant voltage? Is this the purpose of the dropping resistor?

Yes the voltage is always switched between zero volts and 12 volts, its the length of time that it is switched to full voltage that controls the current that flows. A shorter time reduces the current.

There are two square wave signals of the same phase, that operate the A solenoid. The one from the TCU to the dropping resistor, green/yellow is a 0 to 12 volt duty cycle square wave, that tells the trans how much load is applied to the box by the throttle.
The other is the green/red that is a 0 to 5 volt duty cycle square wave, that is used by the TCU to reduce line pressure for shifting, oil temp, etc.

The dropping resistor is between the two signals to allow them to have opposite duty cycle on times, without one shorting the other.

Eg. when the throttle is on the floor, it's on time is 5% for full line pressure. If a gear change is to take place the TCU will send a cycle on time of, say, 50% to reduce the line pressure. If the resistor was not there the lower on time, would short out the higher on time.

To be able to use the resistor to do this, the throttle signal is a higher voltage, the resistor reduces this to lower 5 volt.

Harvey.

[Trevor]

Those reading should also take into account my previous post No. #27, which has become somewhat overridden.

Originally Posted by oab_au

Yes the voltage is always switched between zero volts and 12 volts, its the length of time that it is switched to full voltage that controls the current that flows. A shorter time reduces the current.

Reducing the time when a given current is applied, can not in fact reduce the current. Current Hours appear to have been invented alongside of Watt Hours. What’s what Mr. Watt?

There are two square wave signals of the same phase, that operate the A solenoid. The one from the TCU to the dropping resistor, green/yellow is a 0 to 12 volt duty cycle square wave, that tells the trans how much load is applied to the box by the throttle. The other is the green/red that is a 0 to 5 volt duty cycle square wave, that is used by the TCU to reduce line pressure for shifting, oil temp, etc.

The dropping resistor is between the two signals to allow them to have opposite duty cycle on times, without one shorting the other.

Exactly what constitutes “opposite duty cycle on times” ? Possibly “different” is the intended meaning.

How could one be “shorting the other.? Possibly “overriding” is the intended meaning.

How can a resistor separate two signals and prevent interference, (one shorting the other) when the only applicable difference constitutes a measure of time?

Eg. when the throttle is on the floor, it's on time is 5% for full line pressure. If a gear change is to take place the TCU will send a cycle on time of, say, 50% to reduce the line pressure. If the resistor was not there the lower on time, would short out the higher on time.

To be able to use the resistor to do this, the throttle signal is a higher voltage, the resistor reduces this to lower 5 volt. Harvey.

Is it to be presumed that, it’s/its = the, lower = shorter and higher = longer? Does off and on apply to voltage, or the position of the valve?

How can alleged two independent pulsed signals, maintain independent functions within a single pulse width monitoring supply to a single solenoid, without the longer pulse always deciding the outcome? A resistor will separate them appears to be the answer. What is more the as stated 5 volts, does not leave sufficient voltage to operate the solenoid.

[NiftySVX]

So the million dollar question is why do I have a near constant 2.15v at the connector for the transmission, when I have correct voltage outputs for the resistor and for the solenoid at the TCU? And, is this is what is causing my problem?