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.
   • If within 4.8-5.2 volts, refer to Testing for Intermittent Conditions and Poor Connections .
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.

P0651

1. With the ignition OFF, disconnect the harness connector at the A/C pressure sensor.
2. With the ignition ON, measure for 4.8-5.2 volts between the A/C pressure sensor 5-volt reference circuit and ground.
   • If within 4.8-5.2 volts, refer to Testing for Intermittent Conditions and Poor Connections .
   • If over 5.2 volts, test all 5-volt references circuits for a short to voltage. If all circuits tested are OK, replace the A/C pressure sensor.
   • If under 4.8 volts, turn OFF the ignition and test all 5-volt references circuits for a short to ground or any sensor low reference circuit.
3. If all circuits tested are OK, replace the control module.