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Home >> Cadillac >> 2007 >> XLR V >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls And Fuel - 4.4L - DTC P0171 To DTC 00700 >> DTC P0650 >> Circuit/System Testing
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Circuit/System Testing

  1. Ignition OFF, disconnect the harness at the instrument panel cluster (IPC).
  2. Ignition ON, verify that a test lamp illuminates between the ignition circuit 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, replace the IPC.
  3. Connect a test lamp between the control circuit and the ignition circuit.
  4. Command the MIL 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 engine control module (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.
  5. If all circuits test normal, replace the IPC.
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