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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1058 (Transfer Case - Mp 1222/1225/1226-NQG) >> Diagnostic Information and Procedures >> Four-Wheel Drive Does Not Disengage >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2008 GMC Sierra, 2008 GMC Cab & Chassis Sierra, 2008 Chevrolet Silverado, and 2008 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
  1. Check the axle switch signal circuit for a short to voltage.
    • If everything checks normal then go to the next step.
  2. Check the front axle actuator control circuit for a short to ground with the front axle actuator disconnected and the mode selection switch disconnected.
    • If everything checks normal reconnect the mode selection switch and retest. If the circuit shows a short to ground then replace the switch. If the circuit indicates no short to ground then refer to front axle actuator and axle testing.