In my 87 Grand National with a 5.3 gen 3, P59 blue/green PCM, and a 2007ish 4L80e, the torque convertor is not locking up. From the secondary brake switch, I'm providing 12V with no brake applied to the purple pin 33 wire into the blue harness of the PCM. Out of the green harness of the PCM, pin 2 brown goes to to the "S" position on the transmission harness to provide TCC PWM solenoid with a signal. There is no tan/black wire from Pin 42 on the green connector to the transmission for the TCC enable circuit, I believe that is 4L60 only.

Wire tested positive for continuity from the brake switch to the transmission harness. No codes being thrown. My next guess is either the tune is bad / not commanding lockup, or the TCC PWM solenoid needs replacement.

I compared my tune to to a 2003 Express Van with a 6.0 DBW + 4L80e and there is almost no difference in the TCC sections other than some small differences in TCC Apply Pressure Offsets, Release Ramp Rates, and On Rates. Maybe I should segment swap this to my tune? Is there any specific part of the tune I should check to see if it is enabled? K_TCC_Enable_Solenoid_Present is not enabled on either tune.Anyway to check if TCC is commanding lockup without dropping the pan?

Any specific brand of 4L80 TCC PWM solenoid to buy?

 

Me personally I would first before anything, With car on lift in drive . Ground the TCC PWN solenoid and see if anything happens and take that off the table first . If it locks then back to wiring. Clear codes as that test will set one or should. Then atach DVOM or LED type test light to the TCC ground side and when no enagged you should see assumng running 13.8 +- and comand lockup the VOLATGE should go to 0 to 0 or LED turn off ( pos side of either to wire and neg to ground chassis.
If this does not happn check wiring to PCM again and that at right terminal and if so back to tune.

 

You added your other speed sensor for your 4L80e, right?

I'm assuming you got tge information from LT1swap.com on how to do that?

Are you confirming TCC is commanding on? No misfires? Was the torque converter lockup oring on the input shaft checked or replaced? On older transmissions that oring is always flattened out and I replace it whenever I get a change if not rebuilding the unit.

I have L59/4L80e swapped into my 99 Silverado NBS. Both were part-out specials.

 

I checked resistance on the TCC PWM solenoid and it came back within spec at 10.5 ohms. I applied voltage to the 12v pin and then ground to the TCC pin S and heard it click. I’m pretty sure the solenoid is good.

i checked continuity on the wire from the computer back to the pin and the wire is good.

i don’t think the pcm is commanding ground.

 

yes I added the second speed sensor and I did the swap of pins according to lt1swap.com

I don’t believe the PCM is commanding TCC with ground. I need to segment swap the transmission tune from another tune onto mine and see if it makes a difference.

i cannot confirm if the torque convertor lockup o-ring on the input shaft is any good or has ever been replaced as I got the car with the motor and transmission sitting already in it, so doing that is going to be the last step as it’s very difficult. I’m hoping it’s just the tune.

 

Then I would use the DVOM to verify it is not commanding ground and work back from there. Though I dont see much way it cannot do so unless it bad if you have tried it with bidirectional control .
If it is comandng ground as measured then you have a VB-TRANS-ORING-CONVERTER ISSUE. If as measured it is not you have a WIRING-TCM-TUNE ISSUE.