Circuit/System Description
WARNING: This page is about a different car, the 2009 GMC Yukon and 2009 Chevrolet Tahoe. However, it is still accessible from the selected car via links, so may be relevant.
The transmission control module (TCM) continuously monitors the system voltage on the Ignition 1 and the battery circuits. Lower than normal voltage may be inadequate to operate the transmission control solenoids properly. Improper solenoid operation may cause erratic transmission operation and tie-up conditions, which may result in internal damage.