I have a weird one that I can't figure out. Hoping to get some advice and thank you in advance for any! It just started doing this and generally doesn't to it until it's up to temp. When cruising down the road and the TC should lock, it doesn't always lock. The weird part, is that if you press on the gas harder to just shy of downshifting, it will lock it 100% of the time and stay locked as you accelerate and long as I don't press hard enough to make it downshift. Let off the throttle and it's back to unlocked and won't lock until you give it a decent amount of throttle. The TPS measures right and increases smooth all the way up to just shy of 4v at full open. Any ideas of what could be going on? Thanks again!

 

It's acting like a bad TPS, but you said it measures okay. How's the shifting in general? Sloppy or sharp? I'm wondering of the throttle body-> trans cable needs adjusted. Maybe measure the resistance of the shift solenoid. Brake lights working correctly, as that also tells the tcm to unlock the torque converter.