4L80 Won't Lock Converter

[TurboJ4000]

Hello,

I've been tuning a LQ4 and 4L80 combo that is in a 2004 GMC chassis but its a 2001 LQ4 with some other odds and ends. The tune is from the 2001 Silverado which from the factory came with the 4L80 so I'm not sue why it wont lock up.

I have played with the misfire tables and adjusted the speeds up and down to try and get it to lock but no avail. I have tried to command the TCC lock up which I can see the TCC applied goes to "YES" when I force it in the scanner but it still wont lock.

With the converter unlocked the trans is getting pretty hot and I cant get much time tuning the MAF/VE tables with the trans about to burn up.

Can you guys possibly take a look and tell me if anything is wrong that you can see? I did compare this file to stock 2004 and 2001 repository files and there is nothing unusual that I can see.

Hopefully my tune and logs attached properly this is my first post asking for help after reading for the last several years in the planning.

TCC wont lock up commanded or not.hpl

Drive back from town one 70mph pull no lock up 1-2-23.hpl

Jeep Step 19.hpt

[Alvin]

If it will not log with the scanner commanding it to do it's likely a mechanical issue.

[TurboJ4000]

If it will not log with the scanner commanding it to do it's likely a mechanical issue.

Well that makes sense but before I go tear things apart to see if I can resolve that, what is the correct way to command lock up in the scanner? I can't remember all the options now but I may not have been doing that correctly?

And even if there is an issue in the transmission doesn't that mean there is possibly two issues? If the tune never asks for lock up then I need to fix that also.

[blindsquirrel]

Looking at stuff on a screen will only get you so far, sometimes you have to go real-world and poke at wires and stuff.

screenshot.09-01-2023 12.05.07.png

Since everything works except TCC it's probably safe to assume you have good +12v at E/20-way, but do you have +12v at TCC solenoid A, inside the pan? Does S/20-way go to ground when you command TCC in the scanner - is the PCM capable of supplying a ground there? And if it does, does the ground make it all the way to TCC solenoid B term? What's the ohms of the TCC solenoid measuring between E & S at the trans 20-way?

[TurboJ4000]

I checked the resistance of the tic solenoid from the terminal tonight 10.6 so I?m in range for the later model specs.

I also confirmed the tic control/ground wire from the transmission plug to the PCM connector is good so I would think that is fine. The PCM shifts and works everything else in the trans and engine so the pcm itself has a good ground.

I may not have been forcing the lock up properly in the scanner so I?m going to mess with that while the truck is in the air this weekend. If I can?t get it to lock on it?s out I?ll try jumping the S pin to ground and see if it locks that way.

And I didn?t confirm the 12v on the power pin to the transmission but the fact that it shifts gears I think means that?s not the issue.

[TurboJ4000]

Well I have figured out why it won?t lock but still can?t fix it.

I don?t know how I missed it before but it?s got P1860 DTC code. But I can?t figure out why.

I?ve replaced the TCC solenoid and that didn?t change it. I?ve gone through all the wiring and everything is correct and not damaged/grounded out or bad connections etc.

I did wire in a switch to be able to ground the tcc myself and it works correctly and does lock the converter so I don?t think it?s a mechanical problem at this point.

My only other idea is a faulty PCM but is that a common issue?

[blindsquirrel]

Conditions for Setting the DTC

All conditions for running the DTC are met, and either of the following conditions occur for 4.3 out of 5 seconds.
? The PCM commands the TCC PWM solenoid valve to OFF (0 percent) and the voltage input remains low (zero volts).
? The PCM commands the TCC PWM solenoid valve to ON (100 percent) and the voltage input remains high (B+).

screenshot.15-04-2023 10.26.40.png

Did you cut the wire between 'S' & C2 pin 2 to add your switch, or tee into it?

Does C2 pin 2 change state when you command TCC on/off?

Have you followed the diag for P1860? Looks to me like there's more that can cause this than just the TCC wiring.

[TurboJ4000]

Well I figured it out. I just pulled the pcm apart to look for anything burned up and realized that the C2 Pin 2 was broken off in the connector.

I was able to push the pin further out from the backside and make contact. I just took it for a drive and it?s all good! Holy crap that?s exciting.