Technical Service Bulletin PIT4989B — 2013 GMC SIERRA DENALI

This Preliminary Information communication provides the technician with a list of modules to check for communication with the scan tool, if the navigation radio does not display the current Hybrid mode. Dealer will use a scan tool to check communication with Accessory Direct current Power Control Module, Air Condition control module, Drive Motor Generator Power Inverter Module, Engine Control Module, Battery Energy Control Module, and Transfer Case Control Module. Repair the loss of communication with the affected module and the power flow should return to the radio display.