ECM

DTC P0641 or P0651 (ECM)

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provide an overview of each diagnostic category.

DTC Descriptors
DTC P0641
- 5-Volt Reference 1 Circuit

DTC P0651
- 5-Volt Reference 2 Circuit

Circuit/System Description

The engine control module (ECM) has 2 internal 5-volt reference circuits. Each internal reference circuit provides external 5-volt reference circuits to more than one sensor. A short to ground or short to voltage on one external 5-volt reference circuit can affect all the components connected to the same internal 5 V reference circuit.

Conditions for Running the DTC

* The ignition is in Run or Crank.
* The ignition voltage is greater than 6.0 V.
* The reduced engine power is Inactive.
* DTCs P0641 and P0651 run continuously when the above conditions are met.

Conditions for Setting the DTC

The ECM detects the 5-volt reference is out of range for less than 1 s.

Action Taken When the DTC Sets

DTCs P0641 and P0651 are Type A DTCs.

Conditions for Clearing the MIL/DTC

DTCs P0641 and P0651 are Type A DTCs.

Diagnostic Aids

* The 5-volt reference 1 circuit provides 5 V to the following sensors:

- Manifold absolute pressure (MAP) sensor
- Fuel tank pressure (FTP) sensor
- Accelerator pedal position (APP) sensor 2
- Engine oil pressure (EOP) sensor
- Air conditioning (A/C) refrigerant pressure sensor
- Camshaft position sensor
- Barometric pressure (BARO) sensor

* The 5-volt reference 2 circuit provides 5 V to the following sensors:

- APP sensor 1
- Throttle position sensor 1 and 2
- Crankshaft position sensor

* It may be possible to locate the fault by disconnecting one component at a time from the affected 5-volt reference circuit while viewing the 5-Volt Reference Circuit Status parameter on the scan tool. The scan tool parameter will change from Fault to OK when the source of the fault is disconnected. If all 5-volt reference components have been disconnected and a fault is still indicated, the fault may exist in the wiring harness.

Reference Information
Schematic Reference

Engine Controls Schematics ([1][2]Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Verification

1. Ignition OFF, open the hood to disable the Auto-Stop function. Refer to Hybrid Modes of Operation Description (Hybrid Modes of Operation).
2. Ignition ON, verify the scan tool hood position parameter displays Open.

• If the hood position does not display Open, refer to Diagnostic Trouble Code (DTC) List - Vehicle (Diagnostic Trouble Code (DTC) List - Vehicle) for DTC P254F.

3. Ignition ON, observe the scan tool 5-volt reference 1 and 2 circuit status parameters. The parameters should display OK.
4. Ignition ON, observe the DTC information with a scan tool. DTC P0641 and P0651 should not set.
5. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing

Note: Additional DTCs may set when disconnecting components.

1. Ignition OFF, disconnect the harness connector of all sensors for the applicable DTC. Refer to Diagnostic Aids for the appropriate sensors.
2. Ignition ON, measure for 4.8-5.2 V between one of the 5-volt reference circuits and ground.

• If less than the specified range, test for a short to ground on the 5-volt reference circuit for each affected component. If all circuits test normal, replace the K20 ECM.
• If greater than the specified range, test for a short to voltage on the 5-volt reference circuit for each affected component. If all circuits test normal, replace the K20 ECM.

Note: A short to voltage on the signal circuit of certain components may cause this DTC to set.

3. Connect each component associated with the 5-volt reference circuit, one at a time, while monitoring the appropriate scan tool 5 V Reference Voltage parameter. Verify the voltage remains between 4.8-5.2 V.

• If not within the specified range when a component is connected, test the signal circuit for a short to voltage. If the circuit tests normal, replace the component.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Accelerator Pedal Position Sensor Replacement (Service and Repair)
* Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement (Non-HP2).
* Barometric Pressure Sensor Replacement (Service and Repair)
* Camshaft Position Sensor Replacement (Service and Repair)
* Crankshaft Position Sensor Replacement (Service and Repair)
* Engine Oil Pressure Sensor and/or Switch Replacement (Service and Repair)
* Fuel Tank Pressure Sensor Replacement (Service and Repair)
* Manifold Absolute Pressure Sensor Replacement (Service and Repair)
* Throttle Body Assembly Replacement (Removal and Replacement)
* Control Module References (Programming and Relearning) for ECM replacement, setup, and programming