I need to throw this out there and get additional ideas:

'94 LT1 / 4L60E. TCC intermittently unlocks on the highway. The PCM is telling the trans to do it.

I have swapped:
  • TPS
  • brake pedal switch
  • transmissions (unrelated - lost reverse due to the 93-95 design flaw)
  • Found ECT connector at water pump was corroded and intermittently open circuit (causing PCM to think ECT was -40C - but this only caused 1/3 of the unlock events). I cleaned this.


I did NOT tweak the tune other then unchecking "TCC release at low TPS" and "TCC release at rapid TPS decrease."

I can post a datamaster log if you like - there is nothing obvious to me in the logs that is indicating an unlock.

I never got around to swapping PCMs but can if maybe there's a possibility that there's a bad input?

What else controls TCC lock?