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HOMESERVICE MANUALSPONTIAC2008GRAND PRIX BASEREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 397 (HVAC SYSTEM - AUTOMATIC)DIAGNOSTIC INFORMATION AND PROCEDURESAIR CONDITIONING COMPRESSOR MALFUNCTIONCIRCUIT/SYSTEM TESTING
2008 Pontiac Grand Prix Base

Circuit/System Testing

2008 Pontiac Grand Prix BaseSECTION 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 A/C COMP relay.
  2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal G8 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 ignition circuit terminal E8 and ground.
    • If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition circuit fuse is open, test or replace the A/C COMP relay.
  4. Verify that a test lamp illuminates between the B+ circuit terminal E7 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 for a short to ground.
  5. Disconnect the harness connector at the A/C compressor clutch.
  6. Test for less than 1.0 ohm between the A/C compressor clutch ground circuit terminal B and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  7. Connect the harness connector at the A/C compressor clutch.
  8. Connect a 10A fused jumper wire between the B+ circuit terminal E7 and the control circuit terminal G8. Verify the A/C compressor clutch is activated.
    • If the A/C compressor clutch does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the A/C compressor clutch.
  9. Connect a test lamp between the ignition circuit terminal E8 and the control circuit terminal G7.
  10. Command the A/C relay 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 ECM.
    • 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 ECM.
  11. If all circuits test normal, test or replace the A/C COMP relay.
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Stop DIY work and contact a certified mechanic immediately if any of the following apply:

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