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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1904 (Lighting System) >> Diagnostic Information and Procedures >> Park, License, and/or Tail Lamps Malfunction >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2009 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.

Park Lamp Switch Malfunction

  1. Ignition OFF, disconnect the harness connector at the headlamp switch.
  2. Ignition OFF, verify a test lamp illuminates between B+ and the ground circuit terminal 4.
    • If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify the scan tool Parklamp Switch parameter is Inactive.
    • If not the specified value, test the signal circuit terminal 2 for a short to ground. If the circuit tests normal, replace the BCM.
  4. Install a 3A fused jumper wire between the signal circuit terminal 2 and ground. Verify the scan tool Parklamp 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.
  5. If all circuits test normal, test or replace the headlamp switch.

Park, License, and/or Tail Lamps Malfunction

  1. Ignition OFF, remove the fuse of the inoperative park/marker lamps and inspect.
    • If the fuse is OPEN, test the control circuit of the blown fuse for a short to ground.
  2. Install the fuse.
  3. Ignition OFF, disconnect the park lamp relay.
  4. Ignition ON, verify 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.
  5. Verify 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. If the circuit tests normal and the B+ circuit fuse is open, test the control circuit terminal 87 for a short to ground. If the circuit tests normal, test or replace the park lamp relay.
  6. Verify 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.
  7. Disconnect the harness connector at the inoperative park/license/marker lamp.
  8. Ignition OFF, exterior lamps OFF, test for less than 5 ohms between the ground circuit terminal and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  9. Connect the harness connector at the inoperative park/license/marker lamp.
  10. Connect a 20A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the park/license/marker lamps illuminate.
    • If the park/license/marker lamps do not illuminate, test the control circuit for an open/high resistance. If the circuit tests normal, replace the inoperative park/license/marker lamp.
  11. Connect a test lamp between the B+ circuit terminal 85 and the control circuit terminal 86.
  12. Command the Parking Lamps 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.
  13. If all circuits test normal, test or replace the park lamp relay.
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