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New here. I'm retired auto service manager and tech and don't have access to the tools and equipment I used to have so I'm looking for a little help on what might be common to this problem.
My 2010 cobalt LT 140,000 miles had a hard code P0976 and wouldn't shift properly. I replaced both shift solenoids and drove the car on a road trip 3,000 miles, no problems. Then Code came back once. It was not a hard code and shifted fine. Cleared it. A few hundred miles later another CEL and P0700 code, no other codes, but trans hunted all over. It cleared. On short test drive CEL cam back on when I pulled it into manual low. Would not shift properly. I have a very steep driveway and use low to help hold the car back. Codes P0700 and P0976 came back and cleared, but have not driven yet.
 

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I probably would have thought the solenoids being bad at first also. But knowing these cars, they have grounding problems with the TCM. Anything from a bad or corroded connector at the computer or at the transmission. I can’t remember there being any ground straps on the transmission or engine that may cause that issue, but it’s work a look around. I’ve noticed the wiring gets pretty crispy around the engine and transmission on these cars, that could also be a short of some sort in the wiring I’d look for.

I would just think it’s either the TCM itself or the wiring knowing the symptoms and codes. And then what was replaced and didn’t fix it.

On a side note. I just did the transmission service on my ‘06 LT with a little over 130k miles. Seems to have taken care of the lock up flutter, what I’d call it. And shifts much smoother. Although it wasn’t really too bad to begin with considering the mileage with no service done.
 

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Discussion Starter #3
I probably would have thought the solenoids being bad at first also. But knowing these cars, they have grounding problems with the TCM. Anything from a bad or corroded connector at the computer or at the transmission. I can’t remember there being any ground straps on the transmission or engine that may cause that issue, but it’s work a look around. I’ve noticed the wiring gets pretty crispy around the engine and transmission on these cars, that could also be a short of some sort in the wiring I’d look for.

I would just think it’s either the TCM itself or the wiring knowing the symptoms and codes. And then what was replaced and didn’t fix it.

On a side note. I just did the transmission service on my ‘06 LT with a little over 130k miles. Seems to have taken care of the lock up flutter, what I’d call it. And shifts much smoother. Although it wasn’t really too bad to begin with considering the mileage with no service done.
Thanks, I've seen a number of posts on you tube about bad grounds on the TCM. I think I'll start looking around there. As far as the trans fluid, I have changed fluid every 30K or less. It's clean as can be inside.
 

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I think I have found the problem. The wiring harness from the PCM was worn through the flexible plastic conduit and four wires were grounding out on the oil filter housing. Repaired harness and just drove about 100 miles with no problems. Happy Day! :)
 

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I need to replace the conduit on mine. It’s falling apart. I just haven’t found any the size that will fit around the wire bundle.
 
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