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Home >> Buick >> 2007 >> Allure CX >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System & Fuel System - 3.8L - DTC P0641 To U0107 >> 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 .
  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 .
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