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Home >> Buick >> 2007 >> Allure CX >> Repair and Diagnosis >> External Pages >> Different car >> Section 23 (Fixed & MOVEABLE Window Systems) >> Diagnostic Information and Procedures >> Rear Window Defogger Malfunction >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2008 Buick LaCrosse and 2008 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the R/DEFOG relay.
  2. Ignition ON, verify a test lamp does not illuminate between the output circuit terminal J1 and ground.
    • If the test lamp illuminates, test output circuit for a short to voltage.
  3. Verify a test lamp illuminates between the B+ circuit terminal J3 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 BATT MAIN 3 fuse is open, test or replace the R/DEFOG relay.
  4. Verify a test lamp illuminates between the B+ circuit terminal K3 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 BATT MAIN 3 fuse is open, test the output circuit terminal for a short to ground.
  5. Disconnect the harness connector at the rear window defogger grid.
  6. Ignition OFF, test for less than 1 ohm of resistance between the ground circuit terminal A and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  7. Connect the harness connector at the rear window defogger grid.
  8. Ignition ON, connect a 40A fused jumper wire between the B+ circuit terminal K3 and the output circuit terminal J1. Verify the rear window defogger grid is activated.
    • If the rear window defogger grid does not activate, test the output circuit terminal for an open/high resistance. If the circuit tests normal, test or replace the rear window defogger grid.
  9. Connect a test lamp between the B+ circuit terminal J3 and the control circuit terminal K1.
  10. Command the rear window defogger 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 voltage. If the circuit tests normal, replace the BCM.
    • 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, replace the BCM.
  11. If all circuits test normal, test or replace the R/DEFOG relay.
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