P0651-SENSOR REFERENCE VOLTAGE 2 CIRCUIT

For a complete wiring diagram, refer to the Wiring Information.

Theory of Operation

The Powertrain Control Module (PCM) contains three internal 5-Volt Sensor Supply sources. Each 5-Volt Supply source is split into parallel circuits to provide 5 Volts to multiple sensors. Sensor Supply 2 provides 5 Volts to the Boost Pressure/Intake Air Temperature Sensor, Fuel Rail Pressure Sensor, Camshaft Position Sensor, and the Accelerator Pedal Position Sensor No.2.

When Monitored:
With the ignition on.
Set Condition:
The Powertrain Control Module (PCM) detects low voltage on the Sensor Supply 2 circuit for 0.10 second.

Possible Causes
ACCELERATOR PEDAL POSITION SENSOR
BOOST PRESSURE/INTAKE AIR TEMPERATURE SENSOR 2
FUEL RAIL PRESSURE SENSOR
CAMSHAFT POSITION SENSOR
5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND
POWERTRAIN CONTROL MODULE (PCM)

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

1. CHECK FOR ACTIVE DTCS

1.	Turn the ignition on.

2.	Using the scan tool, select View DTCs.

Is the status Active for this DTC?

Yes

Go To 2

Perform the INTERMITTENT DTC diagnostic procedure. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

2. CAMSHAFT POSITION SENSOR

1.	Turn the ignition off.

2.	Disconnect the CMP Sensor harness connector.

3.	Turn the ignition on.

4.	Measure the voltage of the (K844) 5-Volt Supply circuit at the CMP Sensor harness connector.

Is the voltage above 4.75 Volts?

Yes

Replace the Camshaft Position Sensor in accordance with the service information.
Perform the PCM VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

Go To 3

3. FUEL RAIL PRESSURE SENSOR

1.	Turn the ignition off.

2.	Disconnect the Fuel Rail Pressure Sensor harness connector.

3.	Turn the ignition on.

4.	Measure the voltage of the (K844) 5-Volt Supply circuit at the Fuel Rail Pressure Sensor harness connector.

Is the voltage above 4.75 Volts?

Yes

Replace the Fuel Pressure Sensor in accordance with the service information.
Perform the PCM VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

Go To 4

4. BOOST PRESSURE/INTAKE AIR TEMPERATURE SENSOR 2

1.	Turn the ignition off.

2.	Disconnect the Boost Pressure/Intake Air Temperature Sensor 2 harness connector.

3.	Turn the ignition on.

4.	Measure the voltage of the (K356) Boost Pressure Sensor 5-Volt Supply circuit at the Boost Pressure/Intake Air Temperature Sensor 2 harness connector.

Is the voltage above 4.75 Volts?

Yes

Replace the Boost Pressure Sensor in accordance with the service information.
Perform the PCM VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

Go To 5

5. ACCELERATOR PEDAL POSITION SENSOR

1.	Turn the ignition off.

2.	Disconnect the Accelerator Pedal Position (APP) Sensor harness connector.

3.	Turn the ignition on.

4.	Measure the voltage of the (K857) Accelerator Pedal Position Sensor No.2 5-Volt Supply circuit at the APP Sensor harness connector.

Is the voltage above 4.75 Volts?

Yes

Replace the Accelerator Pedal Position Sensor in accordance with the service information.
Perform the PCM VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

Go To 6

6. CHECK THE 5-VOLT SUPPLY CIRCUIT FOR A SHORT TO GROUND

1.	Turn the ignition off.

2.	Disconnect the PCM harness connectors.

3.	Measure the resistance between ground and the (K857) Accelerator Pedal Position Sensor No. 2 5-Volt Supply circuit at the APP Sensor harness connector..

4.	Measure the resistance between ground and the (K844) 5-Volt Supply circuit at the CMP Sensor harness connector.

5.	Measure the resistance between ground and the (K356) Boost Pressure Sensor 5-Volt Supply circuit at the Boost Pressure/Intake Air Temperature Sensor 2 harness connector.

Is the resistance above 10k Ohms for each circuit?

Yes

Go To 7

Repair the 5-Volt Supply circuit that measured below 10k Ohms for a short to ground.
Perform the PCM VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

7. POWERTRAIN CONTROL MODULE

1.	Turn the ignition off.

2.	Inspect the (K857) Accelerator Pedal Position Sensor No.2 5-Volt Supply circuit between the APP Sensor and the PCM.

3.	Inspect the (K844) 5-Volt Supply circuit between the CMP Sensor and the PCM.

4.	Inspect the (K844) 5-Volt Supply circuit between the Fuel Rail Pressure Sensor and the PCM.

5.	Inspect the (K356) Boost Pressure Sensor 5-Volt Supply circuit between the Boost Pressure/Intake Air Temperature Sensor 2 and the PCM.

6.	Look for any chafed, pierced, pinched or partially broken wires.

7.	Look for broken, bent, pushed out or corroded terminals.

8.	Perform any Technical Service Bulletins that may apply.

Were any problems found?

Yes

Repair as necessary.
Perform the PCM VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

Replace and program the Powertrain Control Module in accordance with the service information.
Perform the PCM VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

P0651-SENSOR REFERENCE VOLTAGE 2 CIRCUIT

P0651-SENSOR REFERENCE VOLTAGE 2 CIRCUIT

Theory of Operation

Possible Causes