1996 12v dropped out of overdrive one day and won't shift back in. I have replaced the break switch, tps, lockup and overdrive solenoid, make sure my batterys were clean and charged up holding a load. Tranny temp never runs over 140 degrees or slips in any gear shifts perfect locks up in and out no problem but won't even try overdrive. Sometimes if I am driving it when the tranny temp is cold under 120 degress and the drop the rpms below 1500rpm at 55mpg it will shift in and i have to very slowly bring it back up to speed or it shifts right out of overdrive. Is there a tranny temp sensor that can be faulty and causes it to kick out?

 

I believe the temp sensor is in the solenoid pack if I remember correctly. Do you have access to a scanner to watch the pcm to see if it is calling for lock up?

 

Yes, I do have a scan tool. I just pulled a code for governor pressure sensor circuit A and tps over volted.

 

What is the pcm calling for when the torque convertor should be locking up?