P0641
DTC P0641 or P0651
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions 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 manifold absolute pressure (MAP) sensor
* The fuel tank pressure (FTP) sensor
* The accelerator pedal position (APP) sensor 2
* The engine oil pressure (EOP) switch
* The air conditioning (A/C) refrigerant pressure sensor
* The camshaft position (CMP) 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, 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
DTC P0641 and P0651 are Type A DTCs.
Conditions for Clearing the MIL/DTC
DTC P0641 and P0651 are Type A DTCs.
Circuit/System Verification
1. Ignition ON, observe the DTC information with a scan tool. DTCs P0641 and P0651 should not set.
2. If the vehicle passes the Circuit/System Verification test, then operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records list.
Circuit/System Testing
Important:
* Additional DTCs will set when disconnecting the components.
* 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.
2. Ignition ON, measure for 4.8-5.2 volts between one of the 5-volt reference circuits and ground.
• If the voltage is less than the specified value, test for a short to ground on all the 5-volt reference circuits. If all circuits test normal, replace the control module.
• If the voltage is greater than the specified value, test for a short to voltage on all the 5-volt reference circuits for each component associated with the appropriate 5-volt reference circuit. If all circuits test normal, replace the control module.
3. Connect each component associated with the 5-volt reference circuit, one at a time, while monitoring the voltage. The voltage should not change more than 1 volt.
• If the voltage display increases more than the specified value when a component is connected, test the signal circuit for a short to voltage. If all circuits test normal, replace the control module.
• If the voltage display decreases more than the specified value when a component is connected, replace the component.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
* Control Module References for ECM replacement, setup, and programming
* Accelerator Pedal Position Sensor Replacement
* Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement
* Fuel Tank Pressure Sensor Replacement
* Manifold Absolute Pressure Sensor Replacement
* Throttle Body Assembly Replacement
* Engine Oil Pressure Sensor and/or Switch Replacement
* Camshaft Position Sensor Replacement
* Crankshaft Position Sensor Replacement Verification Tests