The owner of a 2008 Chevy Cobalt hybrid may note a chuggle or stall when coming to a stop. The engine will restart. The engine tachometer will drop to zero and not AutoStop.
There would not be a command for an auto-stop. The engine may restart using the 12V starter and set a DTC P1A6F. This may lead the technician to incorrectly suspect the hybrid components.
A partially or momentarily applied TCC may be caused by a restriction in the transmission cooling system. Note that a possible restriction in the transmission cooling system may not allow a sufficient volume of fluid to properly release the TCC.
To properly diagnose for possible restriction in the transmission cooling system, complete the following:
- Use J45096 or equivalent to flow test the transmission oil cooler pipes.
- If the flow rate is below minimum, check for cooler restriction, cooler lines bent or kinked, and transmission cooler fluid line passages behind the fittings.