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Home >> Buick >> 2008 >> Allure CXL >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System & Fuel System - 3.8L - DTC P0385 To DTC P2108 >> DTC P0650 >> Circuit/System Testing
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Circuit/System Testing

  1. Turn OFF the ignition.
  2. Disconnect the PCM.
  3. Turn ON the ignition with the engine OFF.
    • If the MIL is still ON, test the MIL control circuit for a short to ground.
    • If the MIL control circuit tested OK and the MIL stayed ON, replace the instrument cluster. Refer to Instrument Cluster Replacement .
    • If the MIL control circuit tested OK and the MIL went out when the PCM was disconnected, replace the PCM. Refer to Control Module References for PCM replacement, setup, and programming.
  4. Measure for 12 volts from the MIL ignition voltage circuit in the instrument cluster harness connector to a ground.
    • If there is less than 12 volts, test the MIL ignition voltage circuit for an open, or a short to ground, and an open fuse.
  5. Remove the fuse that supplies voltage to the MIL.
  6. Measure for less than 1 volt from the MIL control circuit in the PCM harness connector to a good ground.
    • If there is more than 1 volt, test the MIL control circuit for a short to voltage.
  7. Install the fuse that supplies voltage to the MIL.
  8. The MIL should illuminate with a 3-amp fused jumper wire connected between the MIL control circuit in the PCM harness connector and a good ground.
    • If the MIL does not illuminate, test the MIL control circuit for an open or high resistance.
    • If the MIL control circuit tests OK, replace the instrument cluster. Refer to Instrument Cluster Replacement .
    • If the MIL does illuminate, but does not when commanded ON with a scan tool, replace the PCM. Refer to Control Module References for PCM replacement, setup, and programming.
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