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DTC B0768: Service 4WD Light Circuit High: Testing

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 1998 GMC Yukon, 1998 GMC Suburban, 1998 GMC Pickup, 1998 GMC Cab & Chassis, and 1998 Chevrolet Tahoe. However, it is still accessible from the selected car via links, so may be relevant.
  1. If ATC system check was performed, go to next step. If system check was not performed, see ATC SYSTEM CHECK  .
  2. Connect scan tool to DLC. Turn ignition to run (engine off). Using scan tool, command SERVICE 4WD light on. If light comes on, go to step 8). If light does not come on, go to next step.
  3. Turn ignition off. Disconnect ATC control module connectors C1 and C2. Disconnect instrument cluster connector. Turn ignition to run position (engine off). Connect a test light between ground and Light Blue/Black wire terminal E2 at ATC control module connector C1. See WIRING DIAGRAMS  . If test light is on, go to next step. If test light is off, go to step 5).
  4. Locate and repair short to voltage in Light Blue/Black wire circuit. When repair is complete, go to step 9).
  5. Turn ignition off. Reconnect instrument cluster connector. Turn ignition to run position (engine off). Connect fused jumper wire between ground and Light Blue/Black wire terminal E2 at ATC control module connector C1. If SERVICE 4WD light is on, go to next step. If SERVICE 4WD light is off, go to step 7).
  6. Replace ATC control module. See REMOVAL & INSTALLATION  . When replacement is complete, go to step 9).
  7. Check instrument cluster printed circuit and SERVICE 4WD light. Repair or replace as necessary. When repair is complete, go to step 9).
  8. Check instrument cluster printed circuit, SERVICE 4WD light and Light Blue/Black wire circuit for intermittent short to voltage. Repair or replace as necessary. When repair is complete, go to next step.
  9. Turn ignition off. Reconnect all disconnected components. Turn ignition to run position (engine off). Using scan tool, command SERVICE 4WD light on then off. If light comes on then goes off, system is functioning properly. If light does not come on then go off, repeat test from step 1).
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