P0651
DTC P0641 or P0651
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.
DTC Descriptors
DTC P0641
- 5-Volt Reference 1 Circuit
DTC P0651
- 5-Volt Reference 2 Circuit
Diagnostic Fault Information
Circuit/System Description
The engine control module (ECM) has 2 internal 5-volt reference circuits called 5-volt reference 1 and 5-volt reference 2. Each reference circuit provides 5-volt reference circuits for more than one sensor. Therefore, a fault condition on one 5-volt reference circuit will affect the other 5-volt reference circuits connected to that reference circuit. The ECM monitors the voltage on the 5-volt reference circuits.
Conditions for Running the DTC
* The ignition is in Unlock, Accessory, Run, or Crank.
* The ignition voltage is more than 5.23 volts.
* DTCs P0641 and P0651 run continuously when the above conditions are met.
Conditions for Setting the DTC
The ECM detects a voltage out of tolerance condition on the 5-volt reference 1 or 2 circuit for more than 0.5 second.
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 volts to the following sensors:
* The manifold absolute pressure (MAP) sensor
* The fuel tank pressure (FTP) sensor
* The air conditioning (A/C) refrigerant pressure sensor
* The accelerator pedal position (APP) sensor 2
* The engine oil pressure (EOP) sensor
* The camshaft position (CMP) sensor
The 5-volt reference 2 circuit provides 5 volts to the following sensors:
* The APP sensor 1
* The throttle position (TP) sensor 1 and 2
* The crankshaft position (CKP) sensor
* The brake booster vacuum 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 (Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
Electrical Information Reference
* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Diagnostic Trouble Code Descriptions)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
Ignition ON, observe the scan tool 5-volt reference 1 and 2 parameters. The reading should display Circuit OK for a normally operating system.
Circuit/System Testing
Important: A short to voltage on the signal circuit of certain components may cause this DTC to set.
1. Ignition OFF, disconnect the harness connector of all appropriate sensors for the applicable DTC. Refer to Diagnostic Aids for appropriate sensors.
2. Ignition ON, measure for 4.8-5.2 volts between one of the 5-volt reference circuits and ground.
• If less than the specified range, test for a short to ground on all the 5-volt reference circuits. If all circuits test normal, replace the ECM.
• If greater than the specified range, test for a short to voltage on all of the 5-volt reference circuits. If all circuits test normal, replace the ECM.
3. Connect each component associated with the 5-volt reference circuit, one at a time, while monitoring the voltage. Verify the voltage remains between 4.8-5.2 volts.
• 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 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 (Service and Repair)
* Manifold Absolute Pressure Sensor Replacement (Service and Repair)
* Power Brake Booster Vacuum Sensor Replacement (Service and Repair)
* Throttle Body Assembly Replacement (Removal and Replacement)
* Control Module References (Programming and Relearning) for ECM replacement, setup, and programming