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Circuit/System Testing

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

Headlamp Leveling Actuator Malfunction

  1. Ignition OFF, disconnect the harness connector at the headlamp leveling module.
  2. Ignition OFF, scan tool OFF, exterior lamps OFF, test for less than 5.0 ohms of resistance between the ground circuit terminal 24 and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, test for B+ between the voltage circuit terminal 12 and ground.
    • If less than the specified range, test the voltage circuit for a short to ground or an open/high resistance.
  4. Ignition OFF, reconnect the headlamp leveling control module harness connector.
  5. Disconnect the harness connector at the inoperative headlamp leveling actuator.
  6. Ignition ON, verify that a test lamp illuminates between the low reference circuit terminal 2 and B+.
    • If the test lamp does not illuminate, test the low reference circuit for a short to voltage or and open/high resistance. If the circuit tests normal, replace the headlamp leveling module.
  7. Ignition OFF, connect a test lamp between the control circuit terminal 1 and the low reference circuit terminal 2.
  8. Ignition ON, headlamps ON, perform the headlamp motor test with a scan tool. The test lamp should turn ON then OFF as the motor test is performed.
    • If the test lamp is always ON, test the control circuit terminal 1 for a short to voltage. If the circuit tests normal, replace the headlamp leveling module.
    • If the test lamp is always OFF, test the control circuit terminal 1 for a short to ground or an open/high resistance. If the circuit tests normal, replace the headlamp leveling module.
  9. Ignition OFF, connect a test lamp between the control circuit terminal 3 and the low reference circuit terminal 2.
  10. Ignition ON, headlamps ON, perform the headlamp motor test with a scan tool. The test lamp should turn ON then OFF as the motor test is performed.
    • If the test lamp is always ON, test the control circuit terminal 3 for a short to voltage. If the circuit tests normal, replace the headlamp leveling module.
    • If the test lamp is always OFF, test the control circuit terminal 3 for a short to ground or an open/high resistance. If the circuit tests normal, replace the headlamp leveling module.
  11. Ignition OFF, connect a test lamp between the control circuit terminal 4 and the low reference circuit terminal 2.
  12. Ignition ON, headlamps ON, perform the headlamp motor test with a scan tool. The test lamp should turn ON then OFF as the motor test is performed.
    • If the test lamp is always ON, test the control circuit terminal 4 for a short to voltage. If the circuit tests normal, replace the headlamp leveling module.
    • If the test lamp is always OFF, test the control circuit terminal 4 for a short to ground or an open/high resistance. If the circuit tests normal, replace the headlamp leveling module.
  13. Ignition OFF, connect a test lamp between the control circuit terminal 6 and the low reference circuit terminal 2.
  14. Ignition ON, headlamps ON, perform the headlamp motor test with a scan tool. The test lamp should turn ON then OFF as the motor test is performed.
    • If the test lamp is always ON, test the control circuit terminal 6 for a short to voltage. If the circuit tests normal, replace the headlamp leveling module.
    • If the test lamp is always OFF, test the control circuit terminal 6 for a short to ground or an open/high resistance. If the circuit tests normal, replace the headlamp leveling module.
  15. If all circuits test normal, replace the inoperative headlamp leveling actuator.

Suspension Position Sensor Malfunction - Front

  1. Ignition OFF, disconnect the harness connector at the LF suspension position sensor.
  2. Ignition OFF, verify that a test lamp illuminates between B+ and the low reference circuit terminal C.
    • If the test lamp does not illuminate, test the low reference circuit for an open/high resistance.
  3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal A and ground.
    • If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the headlamp leveling module.
    • If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the headlamp leveling module.
  4. Verify the scan tool front leveling position sensor parameter is less than 0.5 volts.
    • If greater than the specified range, test the signal circuit terminal B for a short to voltage. If the circuit tests normal, replace the headlamp leveling module.
  5. Install a 3A fused jumper wire between the signal circuit terminal B and the 5-volt reference circuit terminal A. Verify the scan tool front leveling position sensor parameter is greater than 4.49 volts.
    • If less than the specified range, test the signal circuit for short to ground or an open/high resistance. If the circuit tests normal, replace the headlamp leveling module.
  6. If all circuits test normal, test or replace the LF suspension position sensor.

Suspension Position Sensor Malfunction - Rear

  1. Ignition OFF, disconnect the harness connector at the LR suspension position sensor.
  2. Ignition OFF, verify that a test lamp illuminates between B+ and the low reference circuit terminal C.
    • If the test lamp does not illuminate, test the low reference circuit for an open/high resistance.
  3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal A and ground.
    • If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the headlamp leveling module.
    • If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the headlamp leveling module.
  4. Verify the scan tool rear leveling position sensor parameter is less than 0.5 volts.
    • If greater than the specified range, test the signal circuit terminal B for a short to voltage. If the circuit tests normal, replace the headlamp leveling module.
  5. Install a 3A fused jumper wire between the signal circuit terminal B and the 5-volt reference circuit terminal A. Verify the scan tool rear leveling position sensor parameter is greater than 4.49 volts.
    • If less than the specified range, test the signal circuit for short to ground or an open/high resistance. If the circuit tests normal, replace the headlamp leveling module.
  6. If all circuits test normal, test or replace the LR suspension position sensor.
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