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Chevy Transmission Issues

This bulletin applies to 2007-2008 Chevy Cobalt, Malibu and HHR vehicles equipped with the 4T45E transmission.

Non-BAS hybrid vehicles:

The customer may complain about a chuggle or stall when coming to a stop. The engine will restart. This may be caused by a momentarily applied torque converter causing excessive loads on the engine.

BAS hybrid vehicle:

If this condition is experienced on a BAS hybrid, the engine tachometer will drop to zero and not Auto Stop. 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. 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 transmission cooling system restriction, complete the following:

  • Use J45096 or equivalent to flow test the transmission oil cooler pipes. If the flow rate is below minimum, check the following areas:

  a. The transmission cooler for restriction.

  b. Transmission cooler lines for bends or kinks.

  c. Transmission cooler fluid line passages (behind the fittings) for restriction.

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