I have a stock 08 GXP with 66,000 miles. After changing batteries out, the speedometer would jump erratically. Shortly after that, while coming to a stop, the car will stall at idle. It almost seems as if it's not downshifting or the torque converter isn't disengaging.
I had the TCM flashed and reprogrammed. That fixed the issue for about 5 days, then it picked up where it left off. Mechanic is wanting to install a new one to see if that fixes the issue.
Has anyone had this issue before? There are no codes or lights being displayed either.