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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 439 (Lighting System) >> Diagnostic Information and Procedures >> Headlamps Malfunction (With T4Q) >> Circuit/System Verification

Circuit/System Verification

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  1. Ignition ON, observe the scan tool Headlamp Switch parameter while turning the headlamp switch ON and OFF. The reading should change between Active and Inactive.
    • If the reading does not change between the specified values, refer to Headlamp Switch Malfunction.
  2. Observe the scan tool Auto Hdlp. Disable Sw. parameter while turning the headlamp switch ON and OFF. The reading should toggle between Active and Inactive.
    • If the reading does not change between the specified values, refer to Headlamp Switch Malfunction.
  3. Observe the scan tool Flash to Pass Switch parameter while applying and releasing the turn signal/multifunction switch. The reading should toggle between Active and Inactive.
    • If the reading does not change between the specified values, refer to Turn Signal/Multifunction Switch Malfunction.
  4. Observe the scan tool High Beam Select Switch parameter while applying and releasing the high beam select switch. The reading should toggle between Active and Inactive.
    • If the reading does not change between the specified values, refer to Turn Signal/Multifunction Switch Malfunction.
  5. Command the Low Beams ON and OFF with a scan tool. The low beam headlamps should turn ON and OFF when commanded.
    • If the low beam headlamps do not turn ON and OFF when commanded, refer to Headlamps Malfunction - Low Beam.
  6. Command the High Beams ON and OFF with a scan tool. The high beam headlamps should turn ON and OFF when commanded.
    • If the high beam headlamps do not turn ON and OFF when commanded, refer to Headlamps Malfunction - High Beam.
  7. Observe the low beam, high beam, park and marker lamp LEDs at each headlamp assembly. All LEDs should illuminate when commanded ON
    • If all LEDs illuminate when commanded and the Service Headlamp Assembly indicator is ON, refer to Headlamp Outage Detection Malfunction.
  8. Command the Lamp Test ON and OFF with a scan tool. The lights on indicator, high beam indicator and service headlamp assembly indicator should turn ON and OFF when changing between the commanded states.
    • If the lights on indicator, high beam indicator and service headlamp assembly indicator illuminate during the test, replace the BCM.
    • If the lights on indicator, high beam indicator and service headlamp assembly indicator do not illuminate during the test or remain illuminated at all times, replace the instrument cluster.
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