Hello Scotty. Im an honest mechanic like you for 25 plus years. My personal vehicle has me stumped. Its a 2012 Chevy Colorado street package 3.7 liter 4L60e automatic. No codes present. The torque converter is unlocking and locking between 40-50 mph while cruising. I have maintained the vehicle trans fluid changed 4 times with 115k miles. The only anomaly ive found is during live scan the tps is reading 28% at idle 82% wot. Do you think the tps is causing the trans to unlock do to high reading? Tps reads 30-40% during light throttle cruising with no codes present. Thanks for your time and input.
My 2000 camaro had the same issue around 40-50 mph at low load. It felt like it was going in & out of overdrive. My local buddy is really good with these trans and he knew it was the TCC valve before he even saw the car. He was right. Not sure if this applies here, also didnt have access to a scan tool or a tps issue. Seems like your tps is alittle wonky though. I'd have to think that the torque converter would unlock itself if it feels like it needs to shift, and it would want to shift based on the throttle input that the computer sees. So if the computer is getting a bad reading it might be messing with the transmission. Just posting my thoughts...
The tcc was my first thought but the tps reading high makes me question that first since when you accelerate the converter unlocks. I figure if it thinks the throttle is accelerating it could be the cause.
The Colorados are famous for weird electrical issues. I'd start simple and check all connections and grounds for looseness and corrosion. Then go from there.
Yup. I've already had to replace the a/c relay and under dash harness along with cleaning up the under hood ground with a dremel and then sealing it with rustolem. I've read it could be the harness inside the tranny pan. My buddy is getting me in Saturday to scan it on the factory tools they have at Cadillac. I'll go from there.