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Circuit/System Testing: Notes

WARNING: This page is about a different car, the 2009 GMC Canyon and 2009 Chevrolet Colorado. 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 and panel dimmer switch.
  2. Verify that a test lamp illuminates between the ground circuit terminal 3 and B+.
    • If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify the scan tool Headlamp ON Switch parameter is Inactive.
    • If not the specified value, test the signal circuit terminal 4 for a short to ground. If the circuit tests normal, replace the BCM.
  4. Verify the scan tool Headlamp OFF 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 4 and ground. Verify the scan tool Headlamp ON 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 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.
  7. If all circuits test normal, test or replace the headlamp and panel dimmer switch.

Headlamp Dimmer Switch Malfunction

  1. Ignition OFF, disconnect the inline harness connector X204.
  2. Test for less than 5 ohms between the ground circuit terminal B10 and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, headlamps ON, verify the scan tool Headlamp ON switch parameter is Active.
    • If not the specified value, test the signal circuit terminal A10 for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
  4. Verify the scan tool high beam select switch parameter is Inactive.
    • If not the specified value, test the signal circuit terminal A11 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 A10 and the ground circuit terminal B10. Verify the scan tool Headlamp ON switch parameter is active.
    • If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
  6. Install a 3A fused jumper wire between the signal circuit terminal A11 and the ground circuit terminal B10. Verify the scan tool high beam select switch parameter is active.
    • If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
  7. If all circuits test normal, test or replace the turn signal/multifunction switch.

Headlamp Malfunction - Low Beam

  1. Ignition OFF, disconnect the HDLP relay.
  2. Verify that a test lamp does not illuminate between the control circuit terminal 30 and B+.
    • If the test lamp illuminates, test the relay control circuit for a short to voltage.
  3. Verify that a test lamp illuminates at the B+ circuit terminal 86 and ground.
    • If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  4. Verify that a test lamp illuminates at the B+ circuit terminal 87 and ground.
    • If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  5. Install a 10A fused jumper wire between the B+ circuit terminal 87 and the control circuit terminal 30. The low beam headlamps should illuminate.
    • If the low beam headlamps do not illuminate, test the control circuit for a short to ground or an open/high resistance.
  6. Connect a test lamp between the relay control circuit terminal 85 and ground. With a scan tool command the Headlamps ON and OFF. The test lamp should turn ON and OFF between the commanded states.
    • If the test lamp is always ON, test the relay control circuit for a short to ground. If the circuit tests normal, replace the BCM.
    • If the test lamp is always OFF, test the relay control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
  7. Ignition OFF, disconnect the harness connector at the inoperative headlamp.
  8. Test for less than 5.0 ohms 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.
  9. Connect a test lamp between the control circuit terminal A and ground.
  10. Ignition ON, command the headlamps ON and OFF with a scan tool. The test should turn ON and OFF.
    • If the test lamp is always ON, test the control circuit for a short to voltage.
    • If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance.
  11. If all circuits test normal, replace the inoperative headlamp.

Headlamp Malfunction - High Beam

  1. Ignition OFF, disconnect the BEAM SEL relay.
  2. Verify that a test lamp illuminates between the control circuit terminal 87 and B+.
    • If the test lamp does not illuminate, test the control circuit for an open/high resistance.
  3. Verify a test lamp illuminates between the ground circuit terminal 30 and B+.
    • If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  4. Verify a test lamp illuminates between the ground circuit terminal 85 and B+.
    • If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  5. Connect a test lamp between the relay control circuit terminal 86 and ground. Command the High Beams ON and OFF with a scan tool. The test lamp should turn ON and OFF between the commanded states.
    • If the test lamp is always ON, test the relay control circuit for a short to ground. If the circuit tests normal, replace the BCM.
    • If the test lamp is always OFF, test the relay control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
  6. Ignition OFF, disconnect the harness connector at the inoperative high beam headlamp.
  7. Connect a test lamp between the ground circuit terminal B and B+.
  8. Ignition ON, high beams ON, the test lamp should illuminate.
    • If the test lamp does not illuminate, test the ground circuit for an open high resistance.
  9. Igniton OFF, connect a test lamp between the control circuit terminal A and ground.
  10. Ignition ON, command the Headlamps ON and OFF with a scan tool. The test should turn ON and OFF.
    • If the test lamp is always ON, test the control circuit for a short to voltage.
    • If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance.
  11. If all circuits test normal, replace the inoperative high beam headlamp.
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