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) provide 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 manifold absolute pressure (MAP) sensor
* The fuel tank pressure (FTP) sensor
* AIR pressure sensor
* The exhaust gas recirculation (EGR) valve
The 5-volt reference 2 bus provides 5 volts to the air conditioning (A/C) refrigerant pressure sensor
Conditions for Running the DTC
* DTCs P0601, P0602, P0603, P0604, P0605, P0606, P0607, P060D, P062F, and P2610 are not set.
* The ignition is ON.
* The ignition voltage is more than 9.5 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)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
P0641
Observe the MAP sensor voltage parameter with a scan tool with the ignition ON and the engine OFF. The scan tool should display 3.6-4.8 volts for a normally operating system.
P0651
With the ignition ON and the engine OFF, observe the A/C Refrigerant Pressure-A/C High Side Pressure parameter with a scan tool. The scan tool should display 0.2-4.9 volt or 9-453 psi for a normally operating system.
Circuit/System Testing
P0641
1. With the ignition OFF, disconnect the harness connector at the MAP sensor.
2. With the ignition ON, measure for 4.8-5.2 volts between the MAP sensor 5-volt reference circuit and ground.
3. Command the EGR valve to 100 percent while monitoring the MAP sensor 5-volt reference circuit with a DMM.
• If within 4.8-5.2 volts, refer to Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics).
4. With the ignition OFF, disconnect the harness connector at the EGR valve.
5. With the ignition ON, measure EGR valve 5-volt reference circuit.
• If within 4.8-5.2 volts, replace the EGR valve.
• If over 5.2 volts, check for unexpected voltage at each 5-volt reference circuit or the signal circuit for each component associated with the 5-volt reference.
• If under 4.8 volts, check for a short to ground or low reference circuit at each 5-volt reference circuit.
6. With the ignition ON, use a scan tool to observe the voltage parameter for each component associated with the 5-volt reference circuit while disconnecting each component one at a time.
• If the data parameters change with any component being disconnected, replace the component.
7. If all circuits tested are normal, replace the control module.
P0651
1. With the ignition OFF, disconnect the harness connector at the A/C pressure sensor.
2. With the ignition ON, measure for 4.8-5.2 volts between the A/C pressure sensor 5-volt reference circuit and ground.
• If within 4.8-5.2 volts, refer to Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics).
• If over 5.2 volts, test all 5-volt references circuits for a short to voltage. If all circuits tested are normal, replace the A/C pressure sensor.
• If under 4.8 volts, turn OFF the ignition and test all 5-volt references circuits for a short to ground or any sensor low reference circuit.
3. If all circuits tested are normal, replace the control module.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement (Service and Repair)
* Exhaust Gas Recirculation Valve Replacement (Service and Repair)
* Fuel Tank Pressure Sensor Replacement (NT7) (Service and Repair)Fuel Tank Pressure Sensor Replacement (NU6) (Service and Repair)
* Manifold Absolute Pressure Sensor Replacement (Service and Repair)
* Secondary Air Injection Shutoff Valve Replacement (Secondary Air Injection Shutoff Valve Replacement)
* Control Module References (Programming and Relearning) for powertrain control module (PCM) replacement, setup, and programming