Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. 3. This step will determine if this is a hard or intermittent DTC.
2. 5. This step will determine if there is a 5-volt reference.
3. 7. This step will check to see if the sensor is sending a signal back to the PCM.
4. 11. The PCM supplies 5 volts on the signal circuit. This step determines if that voltage is present, not present, or too much voltage is present.
5. 16. This step determines if the signal circuit is shorted to 5 volts. A normal CAM signal circuit will have 3-5 mA. Any reading over 50 mA indicates a short to 5 volts.

Fig 1: DTC P0251 (Steps 1-10)

Courtesy of GENERAL MOTORS CORP.

Fig 2: DTC P0251 (Steps 11-22)

Courtesy of GENERAL MOTORS CORP.