This Preliminary Information communication provides information to the technician about vehicles that may have Service 4WD message in the Driver Information Center. During inspection technician may find Diagnostic Trouble Code C0398 or C0326 stored in the Transfer Case Control Module. If the vehicle has Regular Production Option Code NP0 and only has diagnostic trouble code C0398 stored in the Transfer Case Control Module, then use Service Programming System to update the Transfer Case Control Module. When working with vehicles equipped NHQ and NQ6 and setting Diagnostic Trouble Code C0398 when operated in areas where the ambient temperature is below 32 Fahrenheit (0 Celsius) use Global Diagnostic System 2 to review the freeze frame failure records, record all findings and Diagnostic Trouble Codes then clear the DTCs and data. Technician will need to operate the vehicle in all ranges and ensure that no Diagnostic Trouble Codes reset. If the vehicle had a Diagnostic Trouble Code C0398 in the Transfer Case Control Module stored with any other Diagnostic Trouble Code such as C0392, C0396, C0306 or other codes related to rotational position sensor or actuator position sensor it is likely that is causing a C0398 to set and replacement of the actuator will likely not repair the vehicle. If no Diagnostic Trouble Codes reset and C0398 was set without other rotational position sensor, or actuator position sensor Diagnostic Trouble Codes then replace the actuator motor with part number 23355888. Dealer will need to contact General Motors Product Quality Center for further assistance.
