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Home >> Pontiac >> 2009 >> Vibe Base, 2.4 0, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 9 (Fixed & MOVEABLE Window System) >> Diagnostic Information and Procedures >> Rear Window Defogger Malfunction >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2009 Cadillac DTS. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the RR DEFOG relay.
  2. Test for less than 1 ohm between the relay coil ground circuit terminal and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify that a test lamp does not illuminate between the relay controlled output circuit terminal and ground.
    • If the test lamp illuminates, test the output circuit for a short to voltage.
  4. Verify that a test lamp illuminates between the relay switch B+ circuit terminal 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 relay controlled output circuit terminal for a short to ground.
  5. Ignition OFF, disconnect the X1 harness connector at the rear window defogger.
  6. Test for less than 1 ohm 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.
  8. Ignition ON, connect a 40A fused jumper wire between the relay switch B+ circuit terminal and the relay controlled output circuit terminal. Verify the rear window defogger grid is activated.
    • If the rear window defogger grid does not activate, test the output circuit 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 relay coil control circuit terminal and ground.
  10. Command the Rear Defog Request 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 HVAC control module.
    • 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 HVAC control module.
  11. If all circuits test normal, test or replace the RR DEFOG relay.
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