DTC P0641 or P0651 Set in ECM
Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provide an overview of each diagnostic category. |
DTC Descriptors
DTC P0641: 5-Volt Reference 1 CircuitDTC P0651: 5-Volt Reference 2 Circuit
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Accelerator Pedal Position (APP) Sensor 1 5-Volt Reference 2 Circuit | P0651 | P2122 | P0651 | -- |
Accelerator Pedal Position (APP) Sensor 2 5-Volt Reference 1 Circuit | P0641 | P2127 | P0641 | -- |
Air Conditioning (A/C) Refrigerant Pressure Sensor 5-Volt Reference 1 Circuit | P0641 | P0532 | P0641 | -- |
Camshaft Position (CMP) Sensor 5-Volt Reference 1 Circuit | P0641 | P0340 | P0641 | -- |
Engine Oil Pressure (EOP) Sensor 5-Volt Reference 1 Circuit | P0641 | P0522 | P0641 | -- |
Fuel Tank Pressure (FTP) Sensor 5-Volt Reference 1 Circuit | P0641 | P0452 | P0641 | -- |
Manifold Absolute Pressure (MAP) Sensor 5-Volt Reference 1 Circuit | P0641 | P0107 | P0641 | -- |
The Crankshaft Position (CKP) Sensor 5-Volt Reference 2 Circuit | P0651 | P0335 | P0651 | -- |
Throttle Position (TP) Sensor 1 and 2 5-Volt Reference 2 Circuit | P0651 | P0122, P0222 | P0651 | -- |
Circuit/System Description
The engine control module (ECM) 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 ECM 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 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 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
| • | 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 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
Connector End View Reference
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References 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.
- Ignition OFF, disconnect the harness connector of all the sensors connected to the 5-volt reference bus for the applicable DTC. Refer to Circuit/System Description.
- Ignition ON, test for 4.8-5.2 volts between one of the 5-volt reference circuits and ground.
- 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.
Important: A short to voltage on the signal circuit of certain components may cause this DTC to set.
| ⇒ | 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. |
| ⇒ | 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 after completing the diagnostic procedure.
| • | Control Module References for ECM replacement, setup, and programming |
