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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 140 (Suspension Control System - Suspension Leveling) >> Diagnostic Information and Procedures >> DTC C0660 >> Circuit/System Testing

Circuit/System Testing

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  1. Ignition OFF, disconnect the harness connector at the ALC compressor.
  2. Ignition ON, verify that a test lamp illuminates between ignition circuit terminal B 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 air compressor.
  3. Connect a test lamp between the control circuit terminal C and the ignition circuit terminal B. Using scan tool, clear all ALC DTCs.
  4. Command the exhaust valve solenoid 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 ESCM.
    • If the test lamp is always OFF, test the control circuit for an open/high resistance. If the circuit tests normal, replace the ESCM.
  5. If all circuits test normal, replace the air compressor.
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