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Home >> Pontiac >> 2008 >> Torrent GXP, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 130 (HVAC System - Manual) >> Diagnostic Information and Procedures >> DTC P0645 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2009 Pontiac Torrent and 2009 Chevrolet Equinox. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the A/C Compressor Clutch Relay.
  2. Ignition ON, verify that a test lamp does not illuminate between the relay control circuit switch supply voltage terminal 30 and relay control circuit switch control terminal 87 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, relay coil voltage supply circuit terminal 85 and ground.
    • If the test lamp does not illuminate, test the ignition circuit for a short to ground or a open/high resistance. If the circuit tests normal and ignition circuit fuse is open, test all components connected to the ignition circuit and replace as necessary.
  4. Verify that a test lamp illuminates between the relay coil B+ supply circuit, terminal, and ground.
    • If the test lamp does not illuminate, test the B+ supply circuit for a short to ground or a open/high resistance. If the circuit tests normal and B+ circuit fuse is open, replace the A/C Clutch Relay.
  5. Disconnect the harness connector at the A/C Clutch Coil.
  6. Test for less than 1.0 ohm of resistance between the A/C Clutch Coil ground circuit terminal 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 Clutch Coil.
  8. Connect a 3-amp fused jumper wire between the B+ supply circuit switch side terminal and control circuit switch side terminal of the A/C Clutch Relay. Verify the A/C Clutch Relay is activated.
    • If the A/C Clutch Relay does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, replace the A/C Clutch Relay.
  9. Connect a test lamp between the coil side of the A/C Clutch Relay ignition circuit terminal, and the control circuit terminal.
  10. Command the A/C Relay output function 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, replace the A/C Clutch Relay.
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