P0641
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 control module has 2 internal 5-volt reference busses called 5-volt reference 1 and 5-volt reference 2. Each reference bus 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 bus. The control module monitors the voltage on the 5-volt reference busses.
The 5-volt reference 1 bus provides 5 volts to the following sensors:
* The air conditioning (A/C) refrigerant pressure sensor
* The manifold absolute pressure (MAP) sensor
* The fuel tank pressure (FTP) sensor
* The accelerator pedal position (APP) sensor 2
* The camshaft position (CMP) sensors
* The engine oil pressure (EOP) sensor
The 5-volt reference 2 bus provides 5 volts to the following sensors:
* The APP sensor 1
* The throttle position (TP) sensor 1 and 2
* The crankshaft position (CKP) sensor
Conditions for Running the DTC
* DTCs P0601, P0602, P0603, P0604, P0606, P0607, P060D, P062F, P1680 and P2610 are not set.
* The ignition is ON.
* 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 control module detects a voltage out of tolerance condition on the 5-volt reference 1 or 2 bus 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.
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: Additional DTCs may set when disconnecting components.
1. Ignition OFF, disconnect the harness connector of all the sensors connected tot he 5-volt reference bus for the applicable DTC. Refer to Circuit/System Description.
Important: A short to voltage on the signal circuit of certain components may cause this DTC to set.
2. Ignition ON, test for 4.8-5.2 volts between one of the 5-volt reference circuits and ground.
• If less than the specified range, test all of the 5-volt reference circuits for a short to ground. 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 or the signal circuit for each component associated with the appropriate 5-volt reference bus for a short to voltage. If all circuits test normal, replace the ECM.
3. Connect each component associated with the appropriate 5-volt reference bus, one at a time, while monitoring the voltage. The voltage should not change more than 1 volt.
• If the voltage display changes more than the specified range when a component is connected, 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 (Service and Repair)
* Control Module References (Programming and Relearning) for ECM replacement, setup, and programming
* Fuel Tank Pressure Sensor Replacement (Service and Repair)
* Manifold Absolute Pressure Sensor Replacement (Service and Repair)
* Throttle Body Assembly Replacement (Removal and Replacement)