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Home >> Chevrolet >> 2007 >> Impala SS >> Repair and Diagnosis >> External Pages >> Different car >> Section 784 (Suspension Control System - Automatic Level Control) >> Diagnostic Information and Procedures >> DTC C0712 (W/O F55) >> Circuit/System Testing
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Circuit/System Testing

WARNING: This page is about a different car, the 2008 Buick Lucerne. However, it is still accessible from the selected car via links, so may be relevant.
    IMPORTANT: Whenever repairing and/or replacing ALC system components, perform Suspension Position Calibration  procedure.
  1. Ignition OFF, disconnect the ELC relay from the rear fuse block.
  2. Ignition ON, verify that 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. If the circuit tests normal, replace the ALC sensor/module.
  3. Verify that 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 or faulty ALC compressor motor. If all circuits test normal, test or replace the ELC relay.
  4. Verify that 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.
  5. Disconnect the harness connector at the air compressor.
  6. Test for less than 1 ohm between the ALC compressor ground circuit terminal D and ground.
    • If greater than 1 ohm, test the ground circuit for an open/high resistance.
  7. Connect the harness connector at the ALC compressor.
  8. Connect a 40A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the ALC compressor is activated.
    • If the ALC compressor does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the ALC compressor.
  9. Connect a test lamp between the B+ circuit terminal 85 and the control circuit terminal 86.
  10. Command the ALC compressor 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 ALC sensor/module.
    • 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 ALC sensor/module.
  11. If all circuits test normal, test or replace the ELC relay.
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