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Home >> Cadillac >> 2006 >> STS V >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - 4.4L - DTC P0506 To P2544 >> DTC P0641 or P0651 >> Circuit/System Testing
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Circuit/System Testing

P0641

  1. Disconnect the MAP sensor electrical connector.
  2. With the ignition ON and the engine OFF, measure for 4.8-5.2 volts between the 5-volt reference circuit terminal C of the MAP sensor and ground.
    • If the voltage is more than 5.2 volts, test for a short to voltage on the 5-volt reference circuits of all the sensors connected to the 5-volt reference 1 bus, test for a short to voltage on the FTP sensor signal circuit.
    • If the voltage is less than 4.8 volts, test for a short to ground on the 5-volt reference circuits of all the sensors connected to the 5-volt reference 1 bus.
  3. Continue to measure the voltage between the 5-volt reference circuit terminal C of the MAP sensor and ground. Monitor the DMM while disconnecting all other sensors connected to the 5-volt reference 1 bus, one at a time.
    • If the voltage returns to 4.8-5.2 volts when a sensor is disconnected, replace the applicable sensor.
  4. Reconnect all sensors.
  5. Measure for 4.8-5.2 volts between the 5-volt reference circuit terminal B of the A/C refrigerant pressure sensor and ground.
    • If the voltage is not between 4.8-5.2 volts, test for a short to voltage on the MAP sensor signal circuit or a faulty MAP sensor.
  6. If all circuits test normal, replace the ECM.

P0651

  1. Disconnect the throttle body electrical connector.
  2. With the ignition ON and the engine OFF, measure for 4.8-5.2 volts between the 5-volt reference circuit terminal 3 and ground.
    • If the voltage is more than 5.2 volts, test for a short to voltage on the 5-volt reference circuits on the 5-volt reference 2 bus.
    • If the voltage is less than 4.8 volts, test for a short to ground on the 5-volt reference circuits on the 5-volt reference 2 bus.
  3. Continue to measure the voltage between the 5-volt reference circuit terminal 3 of the throttle body electrical connector and ground. Monitor the DMM while disconnecting APP sensor 1.
    • If the voltage returns to 4.8-5.2 volts when APP sensor 1 is disconnected, replace the APP sensor.
    • If the voltage did not return to 4.8-5.2 volts when disconnecting the APP 1 sensor, replace the throttle body assembly.
  4. If all circuits test normal, replace the ECM.
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