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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1386 (Transfer Case - Mp 1222/1225/1226-NQG) >> Diagnostic Information and Procedures >> Four-Wheel Drive Indicator Inoperative >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2009 GMC Sierra, 2009 GMC Cab & Chassis Sierra, 2009 Chevrolet Silverado, and 2009 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 an open or high resistance.
    • If everything checks normal then go to the next step.
  2. Check the front axle actuator control circuit pin B at the front axle actuator connector or pin C at the transfer case shift control switch for an open or high resistance.
    • If everything checks normal then short the axle actuator control circuit to ground this should cause the actuator to engage. Remove the short to ground and then short the circuit to ground again, this should cause the actuator to disengage. If the actuator does not operate properly then refer to Four-Wheel Drive Does Not Engage  or Four-Wheel Drive Does Not Disengage . If everything checks normal go to ECM and IPC functionality check.
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