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Circuit/System Testing: Notes

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Headlamp Switch Malfunction

  1. Ignition OFF, disconnect the harness connector at the Headlamp and Panel Dimmer Switch.
  2. Ignition OFF, verify that a test lamp illuminates between B+ and the ground circuit terminal 8.
    • If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify the scan tool Headlamp Switch parameter is INACTIVE.
    • If not the specified value, test the signal circuit terminal 1 for a short to ground. If the circuit tests normal, replace the BCM.
  4. Verify the scan tool Auto Hdlp. Disable Sw. parameter is INACTIVE.
    • If not the specified value, test the signal circuit terminal 3 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 1 and ground. Verify the scan tool Headlamp 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 3 and ground. Verify the scan tool Auto Hdlp. Disable Sw. 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.

Headlamps Malfunction - Low Beam

  1. Ignition OFF, disconnect the HDLP LO/HID Relay.
  2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 87 and ground.
    • If the test lamp illuminates, test the control circuit for a short to voltage.
  3. Verify that a test lamp illuminates between the B+ circuit terminal 30 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 between the B+ circuit terminal 85 and ground.
    • If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
  5. Disconnect the harness connector at the inoperative low beam headlamp.
  6. Ignition OFF, scan tool OFF, exterior lamps OFF, test for less than 5.0 ohms between the listed ground circuit terminal below and ground.
    • low beam headlamp terminal A - X88
    • low beam headlamp terminal B - Z88
    • low beam headlamp terminal 2 - Z75
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  7. Connect the harness connector at the inoperative low beam headlamp.
  8. Connect a 20A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the low beam headlamps are activated.
    • If the low beam headlamps do not activate, and the appropriate LO BEAM headlamp fuse tests normal, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the inoperative low beam headlamp.
  9. Connect a test lamp between the B+ circuit terminal 85 and the control circuit terminal 86.
  10. Command the Low Beam headlamps 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.
  11. If all circuits test normal, test or replace the HDLP LO/HID Relay.

Headlamps Malfunction - High Beam

  1. Ignition OFF, disconnect the X4 connector at the underhood fuse block.
  2. Connect a test lamp between terminal C3 and B+.
  3. Ignition ON, toggle the high beams ON and OFF with a scan tool. The test 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.
  4. If all circuits test normal, replace the underhood fuse block.
  5. Disconnect the harness connector at the inoperative high beam headlamp.
  6. Ignition OFF, scan tool OFF, exterior lamps OFF, test for less than 5.0 ohms between the listed ground circuit terminal below and ground.
    • high beam headlamp terminal A - X88
    • high beam headlamp terminal B - Z88
    • high beam headlamp terminal 1 - Z75
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  7. Connect a test lamp between the listed control circuit terminal and ground.
    • high beam headlamp terminal B - X88
    • high beam headlamp terminal C - Z88
    • high beam headlamp terminal 2 - Z75
  8. Command the high beam headlamps ON and OFF with a scan tool. The test lamp should turn ON and OFF.
    • If the test lamp is always ON, test the control circuit for a short voltage. If the circuit tests normal, replace the underhood fuse block.
    • 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, and the appropriate HI HEADLAMP fuse tests normal, replace the underhood fuse block.
  9. If all circuits test normal, replace the appropriate high beam headlamp.

Turn Signal/Multifunction Switch Malfunction

  1. Ignition OFF, disconnect the harness connector at the turn signal/multifunction switch.
  2. Ignition OFF, verify that a test lamp illuminates between B+ and the ground circuit terminal D.
    • 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 Select 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 an 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 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.
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