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Home >> Hummer >> 2008 >> H3 Base, Automatic >> Repair and Diagnosis >> External Pages >> Different car >> Section 172 (Lighting Systems) >> Diagnostic Information and Procedures >> Front Fog Lamps Malfunction >> Circuit/System Testing

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.

Front Fog Lamp 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 3.
    • If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify that a test lamp does not illuminate between B+ and the front fog lamp switch signal circuit terminal 4.
    • If the test lamp illuminates, test the signal circuit for a short to ground. If the circuit tests normal, replace the IPM.
  4. Install a 3-A fused jumper wire between the signal circuit terminal 4 and the ground circuit terminal 3. Verify the front fog lamps are ON.
    • If the front fog lamps are OFF, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the IPM.
  5. If all circuits test normal, test or replace the turn signal/multifunction switch.

Front Fog Lamps Malfunction

  1. Ignition OFF, disconnect the front fog lamp relay.
  2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal R4 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 R2 and ground.
    • If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the control circuit terminal R3 for a short to ground. If the circuit tests normal, test or replace the front fog lamp relay.
  4. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal R1 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 front fog lamp.
  6. Ignition OFF, scan tool OFF, exterior lamps OFF, test for less than 5.0 ohms between the inoperative front fog lamp ground circuit and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  7. Connect the harness connector at the inoperative front fog lamp.
  8. Connect a 15-A fused jumper wire between the B+ circuit terminal R2 and the relay controlled output circuit terminal R3. Verify the front fog lamps are activated.
    • If the front fog lamps do not activate, test the relay controlled output circuit terminal R3 for an open/high resistance. If the circuit tests normal, test or replace the inoperative front fog lamp.
  9. Connect a test lamp between the B+ circuit terminal R1 and the control circuit terminal R4
  10. Command the front fog lamps ON and OFF with the 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 IPM.
    • If the test lamp is always OFF, test the control circuit for a short to voltage or open/high resistance. If the circuit tests normal, replace the IPM.
  11. If all circuits test normal, test or replace the front fog lamp relay.
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