Action Taken When the DTC Sets

WARNING: This page is about a different car, the 2007 GMC Sierra and 2007 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The TCM requests the ECM to illuminate the malfunction indicator lamp (MIL).
The TCM commands maximum line pressure.
The TCM inhibits 4th gear.
The TCM freezes transmission adaptive functions.
At the time of the first failure, the TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as a Failure Record.
At the time of the second failure, the ECM records the operating conditions when the Conditions for Setting the DTC are met. The ECM stores this information as a Freeze Frame.
The TCM stores DTC P0977 in TCM history during the second consecutive trip in which the Conditions for Setting the DTC are met.