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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 981 (Lighting Systems) >> Diagnostic Information and Procedures >> Headlamps Malfunction >> Circuit/System Verification

Circuit/System Verification

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. Ignition ON, observe the scan tool Headlamp Switch parameter while cycling the headlamp switch between the auto and headlamp position. The parameter should cycle between Active and Inactive.
    • If the parameter does not cycle between the specified values, refer to the Headlamp Switch Circuit Test below.
  2. Observe the headlamps while cycling the headlamp switch between the auto and headlamp position. The low beam headlamps should turn on and off.
    • If 1 or both of the low beam headlamps do not turn on and off, refer to the Low Beam Headlamp Circuit Test below.
  3. Low beam headlamps ON, observe the scan tool High Beam Select Switch parameter while switching the high/low beam select switch between the low and high beam positions. The parameter should cycle between Active and Inactive.
    • If the parameter does not cycle between the specified values, refer to the High/Low Beam Select Switch Circuit Test below.
  4. Connect a test lamp between the relay side of a high beam headlamp fuse and ground.
  5. Verify that the test lamp turns on and off while switching the high/low beam select switch between the low and high beam positions.
    • If the test lamp does not turn on and off while changing between the commanded states, refer to the High Beam Relay Control Circuit Test below
  6. If 1 or both of the high beam headlamps do not turn on and off, refer to the High Beam Headlamp Circuit Test below.
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