converter prematurely locking/TCC solenoid

[getchasum]

I have a problem with the new T locking the converter prematurely. Under normal driving it will stack shifts (short shift) causing the car to lug. The car will be in 3rd with the converter lock by 30 mph. The converter is locking up under normal operation as soon as it shifts into 2nd gear. If I’m under a hard acceleration it does much better of holding the shifts. When I unhook the TCC solenoid the Trans shift points are corrected & car drives nicely, SO I think I have a bad TCC solenoid & replace it with a new GM TCC solenoid. After hooking up the new TCC solenoid the car is back to above described conditions of locking converter prematurely & short shifting, unplug the New TCC solenoid and it drives and shifts great. What gives?
This condition started out of the blue about a month ago with no prior warnings.
The converter will unlock if you tap brake so I guess that rules out that switch & I don’t see how the lock-up command in the chip just all of a sudden could start giving trouble
I want to retain a lock up but the car is a dog with it hook up.

 

[mikestertwo]

Sounds like your TCC lock command is grounded somewhere. Measure the voltage on pin "F" of your ALDL connector (measure between pins A & F) Should read approx. 12 volts. If it's close to 0 volts, then you have a short to ground somewhere. Measure with key on, motor does not have to be running.

 

[getchasum]

Sounds like your TCC lock command is grounded somewhere. Measure the voltage on pin "F" of your ALDL connector (measure between pins A & F) Should read approx. 12 volts. If it's close to 0 volts, then you have a short to ground somewhere. Measure with key on, motor does not have to be running.

Thanks I'll start check, may be the weekend due to job having me nail this week.

Seems I have a closed ground in the TCC lock up circuit when I should not have, causing the converter to lock up after shifting to 2nd, 3rd & 4th gear.

Here's a kicker....I unhook the scan master yesterday and the car is now shifting correctly again. The SM had been in the car for about 7 months with no prior trouble or shifting problems w/ trans. I may have a problem with the ALDL plug some how grounding with other pins.

Glad the trans is now shifting correctly again but it sucks not being able to use the SM. I hate wiring problems