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Home >> Buick >> 2006 >> Allure CX >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - 3.8L - DTC P0451 To DTC P2120 >> DTC P0641 or P0651 >> Circuit/System Testing >> P0641

Circuit/System Testing: P0641

  1. With the ignition OFF, disconnect the harness connector at the MAP sensor.
  2. With the ignition ON, measure for 4.8-5.2 volts between the MAP sensor 5-volt reference circuit and ground.
  3. Command the EGR valve to 100 percent while monitoring the MAP sensor 5-volt reference circuit with a DMM.
  4. With the ignition OFF, disconnect the harness connector at the EGR valve.
  5. With the ignition ON, measure EGR valve 5-volt reference circuit.
    • If within 4.8-5.2 volts, replace the EGR valve.
    • If over 5.2 volts, check for unexpected voltage at each 5-volt reference circuit or the signal circuit for each component associated with the 5-volt reference.
    • If under 4.8 volts, check for a short to ground or low reference circuit at each 5-volt reference circuit.
  6. With the ignition ON, use a scan tool to observe the voltage parameter for each component associated with the 5-volt reference circuit while disconnecting each component one at a time.
    • If the data parameters change with any component being disconnected, replace the component.
  7. If all circuits tested are OK, replace the control module.
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