Service 4WD

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 1999 Oldsmobile Bravada, 1999 GMC Sonoma, 1999 GMC Jimmy, 1999 GMC Envoy, and 1999 Chevrolet S10 Pickup. However, it is still accessible from the selected car via links, so may be relevant.

Light Emitting Diode (LED) is controlled by Instrument Panel Cluster (IPC). LED illuminates when IPC receives Class 2 data from Automatic Transfer Case (ATC) module. LED illuminates when one or more of the following conditions exists:

System related DTC is set.
Instrument cluster cannot communicate with ATC module on Class 2 serial data line.
Instrument cluster receives a Class 2 serial data message from ATC module requesting SERVICE 4WD indicator on.