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Home >> Buick >> 2007 >> Allure CX >> Repair and Diagnosis >> External Pages >> Different car >> Section 19 (Lighting Systems) >> Diagnostic Information and Procedures >> Headlamps Malfunction >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2008 Buick LaCrosse and 2008 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.

Headlamp Switch Malfunction

  1. Ignition OFF, disconnect the harness connector at the headlamp switch.
  2. Ignition OFF, test for less than 5 ohms of resistance between the ground circuit terminal 17 and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify the scan tool Headlamp Off Switch parameter is Inactive.
    • If not the specified value, test the signal circuit terminal 18 for a short to ground. If the circuit tests normal, replace the BCM.
  4. Verify the scan tool Low Beam Switch parameter is Inactive.
    • If not the specified value, test the signal circuit terminal 5 for a short to ground. If the circuit tests normal, replace the BCM.
  5. Install a 3A fused jumper wire between the signal circuit terminal 18 and ground. Verify the scan tool Headlamp Off Switch parameter is Active.
    • If not the specified value, test the signal circuit for a short to voltage or and open/high resistance. If the circuit tests normal, replace the BCM.
  6. Install a 3A fused jumper wire between the signal circuit terminal 5 and ground. Verify the scan tool Low Beam Switch parameter is Active.
    • If not the specified value, test the signal circuit for a short to voltage or and open/high resistance. If the circuit tests normal, replace the BCM.
  7. If all circuits test normal, test or replace the headlamp switch.

Headlamp Dimmer Switch Malfunction

  1. Ignition OFF, disconnect the X1 harness connector at the multifunction turn signal lever.
  2. Ignition OFF, test for less than 5 ohms of resistance between the ground circuit terminal D and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify the scan tool Flash to Pass Switch parameter is Inactive.
    • If not the specified value, test the signal circuit terminal A for a short to ground. If the circuit tests normal, replace the BCM.
  4. Verify the scan tool High Beam Switch parameter is Inactive.
    • If not the specified value, test the signal circuit terminal E for a short to ground. If the circuit tests normal, replace the BCM.
  5. Install a 3A fused jumper wire between the signal circuit terminal A and ground. Verify the scan tool Flash to Pass Switch parameter is Active.
    • If not the specified value, test the signal circuit for a short to voltage or and open/high resistance. If the circuit tests normal, replace the BCM.
  6. Install a 3A fused jumper wire between the signal circuit terminal E and ground. Verify the scan tool High Beam Switch parameter is Active.
    • If not the specified value, test the signal circuit for a short to voltage or and open/high resistance. If the circuit tests normal, replace the BCM.
  7. If all circuits test normal, test or replace the multifunction turn signal lever.

Low Beam Headlamp Malfunction

  1. Ignition OFF, disconnect the HDM.
  2. Ignition OFF, test for less than 1 ohm of resistance between the ground circuit terminal B11 and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify a test lamp illuminates between the B+ circuit terminal A12 and ground.
    • If the test lamp does not illuminate, replace the underhood fuse block.
  4. Install a test lamp between the B+ circuit terminal A12 and the control circuit terminal C12.
  5. Command the Low Beam/DLR ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
    • If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM.
    • If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
  6. Ignition OFF, connect the HDM. Disconnect the harness connector at the appropriate low beam headlamp bulb.
  7. Ignition OFF, test for less than 5 ohm of resistance between the ground circuit terminal B and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  8. Connect a test lamp between the control circuit terminal A and ground.
  9. Ignition ON, command the Low Beam/DLR ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
    • If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the HDM.
    • If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the HDM.
  10. If all circuits test normal, test or replace the low beam headlamp bulb.

High Beam Headlamp Malfunction

  1. Ignition OFF, disconnect the HI BEAM relay.
  2. Ignition ON, verify a test lamp illuminates between the B+ circuit terminal G19 and ground.
    • If the test lamp does not illuminate, replace the underhood fuse block.
  3. Verify a test lamp illuminates between the B+ circuit terminal G20 and ground.
    • If the test lamp does not illuminate, replace the underhood fuse block.
  4. Install a test lamp between the B+ circuit terminal G19 and the control circuit terminal E20.
  5. Command the High Beams ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
    • If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM.
    • If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
  6. Ignition OFF, connect the HI BEAM relay. Disconnect the harness connector at the appropriate high beam headlamp bulb.
  7. Ignition OFF, test for less than 5 ohm of resistance between the ground circuit terminal B and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  8. Connect a test lamp between the control circuit terminal A and ground.
  9. Ignition ON, command the High Beams ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
    • If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the HI BEAM relay.
    • If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the HI BEAM relay.
  10. If all circuits test normal, test or replace the high beam headlamp bulb.
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