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Home >> Cadillac >> 2021 >> CT4 Sport, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 87 (Lighting System - Diagnostic Information And Procedures (2 Of 2)) >> Diagnostic Information and Procedures >> Headlamps Malfunction >> Circuit/System Verification

Circuit/System Verification

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  1. Ignition ON.
  2. Verify there are no related DTCs set.
    • Go to next step: If no related DTCs are set 
  3. Verify each scan tool parameter changes while commanding the appropriate Turn Signal Switch function:
    • Headlamps On Switch parameter changes between Active and Not Requested while commanding the headlamps ON and OFF with the Turn Signal Switch.
    • Automatic Headlamps Disable Switch parameter changes between Active and Not Requested while commanding the automatic lamp control ON and OFF with the Turn Signal Switch.
    • High Beam Select Switch parameter changes between Active and Not Requested while commanding the high beams ON and OFF with the Turn Signal Switch.
    • Headlamps Flash Switch parameter changes between Active and Not Requested while commanding the flash to pass ON and OFF with the Turn Signal Switch.
    • If one or more of the parameters does not change 

      Refer to Circuit/System Testing - Turn Signal Switch Malfunction.

    • Go to next step: If all of the parameters change 
  4. Engine running, headlamps set to AUTO.
  5. Verify the AUTO high beam assist indicator in the P16 instrument Panel Cluster Module turns ON and OFF when pressing the AUTO High Beam Assist button on the Turn Signal Switch.
    • If the indicator does not turn ON and OFF 

      Refer to Circuit/System Testing - Turn Signal Switch Malfunction.

    • Go to next step: If the indicator turns ON and OFF 
  6. Verify the Ambient Light Intensity data parameter value changes appropriately:
    • LX value increases with an incandescent light shined on the B10B Sun Load and Ambient Light and Security Indicator Sensor to simulate bright conditions.
    • LX value decreases with a towel covering the B10B Sun Load and Ambient Light and Security Indicator Sensor to simulate dark conditions.
    • If the value does not change 

      Refer to Circuit/System Testing - Ambient Light Sensor Malfunction

    • Go to next step: If the value changes 
  7. Verify the left and right low beam headlamps turn ON and OFF when commanding the Left and Right Low Beams ON and OFF with a scan tool.
    • If the low beam headlamps do not turn ON and OFF 

      Refer to Circuit/System Testing - Headlamps Malfunction - Low Beam.

    • Go to next step: If the low beam headlamps turn ON and OFF 
  8. Verify the left and right high beams turn ON and OFF when commanding the Left and Right High Beams ON and OFF with a scan tool.
    • If the high beams do not turn ON and OFF 

      Refer to Circuit/System Testing - Headlamps Malfunction - High Beam.

    • Go to next step: If the high beams turn ON and OFF 
  9. A fault is not currently present and may be an intermittent condition.
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