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?
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