This Preliminary Information communication provides information to the technician about vehicles that may have a Service 4WD message on the Driver Information Center when operated below 10 degrees Fahrenheit (-12 Celsius). Technician may find C0398 or C0326 stored in the Transfer Case Control Module. For vehicles with Regular Production Option Code NQH and NQ6 and only setting Diagnostic Trouble Codes C0398 or C0398 and C0326 the replacement of the actuator motor will correct the concern. Dealer will need to contact General Motors Product Quality Center for further assistance. For vehicles with Regular Production Option Code NQH and NQ6 with other transfer case Diagnostic Trouble Codes. If the vehicle had a Diagnostic Trouble Code C0398 in the transfer case control module stored with any other codes 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. For vehicles with Regular Production Option Code NP0 and only have a Diagnostic Trouble Code C0398 stored in the transfer case control module, the technician should insure the transfer case control module calibrations are up-to-date in Tis2Web.
