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Home >> Buick >> 2018 >> Regal GS >> Repair and Diagnosis >> Accessories & Equipment >> Exterior Lights >> Lighting System - Diagnostic Information And Procedures (B388B-P0504) And Symptoms >> Diagnostic Information and Procedures >> Headlamps Malfunction >> Circuit/System Verification

Circuit/System Verification

  1. Ignition ON.
  2. Verify the scan tool Headlamps On Switch parameter changes between Active and Inactive while commanding the headlamp ON and OFF with the headlamp switch.
    • If the parameter does not change 

      Refer to Circuit/System Testing - Headlamp Switch Malfunction.

    • Go to next step: If the parameter changes 
  3. Verify the scan tool Automatic Headlamps Disable Switch parameter changes between Active and Inactive while commanding the automatic lamp control ON and OFF with the headlamp switch.
    • If the parameter does not change 

      Refer to Circuit/System Testing - Headlamp Switch Malfunction.

    • Go to next step: If the parameter changes 
  4. Verify the scan tool Headlamps Flash Switch parameter changes between Active and Inactive while commanding the flash to pass ON and OFF with the turn signal/multifunction switch.
    • If the parameter does not change 

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

    • Go to next step: If the parameter changes 
  5. Verify the scan tool High Beam Select Switch parameter changes between Active and Inactive while commanding the high beams ON and OFF with the turn signal/multifunction switch.
    • If the parameter does not change 

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

    • Go to next step: If the parameter changes 
  6. Verify the left low beam turns ON and OFF when commanding the Left Headlamp Low Beam ON and OFF with a scan tool.
    • If the left low beam does not turn ON and OFF 

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

    • Go to next step: If the left low beam turns ON and OFF 
  7. Verify the right low beam turns ON and OFF when commanding the Right Headlamp Low Beam ON and OFF with a scan tool.
    • If the right low beam does not turn ON and OFF 

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

    • Go to next step: If the right low beam turns ON and OFF 
  8. Low beam headlamps ON, verify the high beams turn ON and OFF when commanding the High Beams ON and OFF with the S78 Turn Signal/Multifunction Switch.
    • 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. Verify the high beam indicator on the instrument cluster turns ON and OFF while commanding the All Indicators ON and OFF with a scan tool.
    • If the high beam indicator does not turn ON and OFF 

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

    • Go to next step: If the high beam indicator turns ON and OFF 
  10. (TQ5/UVG only), verify the automatic high beam control indicator on the instrument cluster turns ON and OFF while commanding the automatic high beam control ON and OFF with the automatic high beam control switch located on the Turn Signal/Multifunction switch.
    • If the automatic high beam control indicator does not turn ON and OFF 

      Refer to Circuit/System Testing - Automatic High Beam Select Switch Malfunction.

    • Go to next step: If the automatic high beam control indicator turns ON and OFF 
  11. All OK.
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