P0641
DTC P0641 or P0651
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 V Reference 1 Circuit
DTC P0651
- 5 V Reference 2 Circuit
Circuit/System Description
The engine control module (ECM) has 2 internal 5 V reference circuits. Each internal reference circuit provides external 5 V reference circuits for more than one sensor. A short to ground or short to voltage on one external 5 V reference circuit can affect all the components connected to the same internal 5 V reference circuit.
Conditions for Running the DTC
* Reduced engine power is not active.
* The ignition is ON.
* The ignition voltage is greater than 6 V.
* The DTCs run continuously when the above conditions are met.
Conditions for Setting the DTC
The ECM detects a voltage out of range condition on the 5 V reference 1 or 2 circuit for greater than 0.5 s.
Action Taken When the DTC Sets
DTCs P0641 and P0651 are Type A DTCs
Conditions for Clearing the DTC
DTCs P0641 and P0651 are Type A DTCs
Diagnostic Aids
The 5 V 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
* Air conditioning (A/C) refrigerant pressure sensor
* Camshaft position sensor
* Engine oil pressure sensor
The 5 V reference 2 circuit provides 5 V to the following sensors:
* APP sensor 1
* Crankshaft position sensor
* Throttle position sensor 1 and 2
It may be possible to locate the fault by disconnecting one component at a time from the affected 5 V reference circuit while viewing the 5 V 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 V 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 End Views By Name)
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. Observe the scan tool 5 V reference 1 circuit status and the 5 V reference 2 circuit status parameters. Verify the parameters display OK.
2. Ignition ON, observe the DTC information with a scan tool. DTCs P0641 and P0651 should not set.
3. Operate the vehicle within the Conditions for Running the DTC. 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 will set when disconnecting the components.
1. Ignition OFF, disconnect the harness connector of all appropriate 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 V reference circuits and ground.
• If less than the specified range, test for a short to ground on the 5 V 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 V 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 V 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 the specified range when a component is connected, test the signal circuit for a short to voltage. If the circuit tests normal, replace the appropriate 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 (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 (Fuel Tank Pressure Sensor Replacement)
* 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