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Home >> Cadillac >> 2006 >> DTS 4.6 9 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - 4.6L - DTC P0403 To P1381 >> DTC P0418 >> Circuit/System Testing
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Circuit/System Testing

  1. With the ignition ON, the engine OFF, and the AIR pump relay enabled with a scan tool, observe the AIR pump relay and the AIR pump while manipulating all related wiring and connectors.
    • If manipulation does affect the relay or the pump, repair the wire harness or connections.
  2. With the ignition ON, the engine OFF, and the pump relay removed, connect a test lamp from the relay coil voltage supply circuit to ground and verify that the test lamp illuminates.
    • If the test lamp does not illuminate, test the voltage supply circuit for an open, high resistance, or a short to ground.
  3. With the ignition ON, the engine OFF, and the pump relay removed, connect a test lamp from the relay coil voltage supply circuit to the relay control circuit and verify that the test lamp does not illuminate.
    • If the test lamp illuminates, test the control circuit for a short to ground. If the circuit test normal, replace the control module.
  4. With the ignition ON, the engine OFF, and the pump relay removed, a test lamp connected from the relay coil voltage supply circuit to the relay control circuit, and the AIR pump relay enabled with a scan tool, verify that the test lamp illuminates.
    • If the test lamp does not illuminate, test the relay control circuit for an open, high resistance, or a short to voltage. If the circuit test normal, replace the control module.
  5. If all circuits and the control module test normal, replace the pump relay.
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