Diagnostic Instructions
| • | Perform the Powertrain On Board Diagnostic (OBD) System Check prior to using this diagnostic procedure. |
| • | 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 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 | -- |
Camshaft Position (CMP) Sensor 5-Volt Reference 1 Circuit | P0641 | P0340 | P0641 | -- |
Crankshaft Position (CKP) Sensor 5-Volt Reference 2 Circuit | P0651 | P0335 | P0651 | -- |
Engine Oil Pressure (EOP) Sensor 5-Volt Reference 1 Circuit | P0641 | -- | P0641 | -- |
Manifold Absolute Pressure (MAP) Sensor 5-Volt Reference 1 Circuit | P0641 | P0107 | P0641 | -- |
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 5-volt reference circuits. The ECM provides the 5-volt reference to various sensors. Each reference circuit provides a 5-volt reference for greater than one sensor. A short to ground or voltage on one of the 5-volt reference circuits will affect all components connected to that 5-volt reference circuit. The ECM monitors the voltage on the 5-volt reference circuits.
Conditions for Running the DTC
| • | The ignition is ON, or the engine is running. |
| • | The ignition voltage is greater than 5.3 volts. |
| • | DTCs P0641 and P0651 run continuously when the above conditions are met. |
Conditions for Setting the DTC
The control module detects a voltage above 5.5 volts, or below 4.5 volts, on either 5-volt reference circuit for greater 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
If a shared 5-volt reference circuit is shorted to ground or shorted to a voltage, other 5-volt reference circuits may be affected.
P0641
The 5-volt reference 1 circuit provides 5 volts to the following sensors:
| • | The manifold absolute pressure (MAP) sensor |
| • | The accelerator pedal position (APP) sensor 2 |
| • | The engine oil pressure (EOP) sensor |
| • | The camshaft position (CMP) sensor |
P0651
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 |
Reference Information
Schematic Reference
Connector End View Reference
Electrical Information Reference
DTC Type Reference
Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Engine Control Module 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.
- Ignition ON, observe the DTC information with a scan tool. DTCs P0641 or P0651 should not set.
- Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at all appropriate sensors for the applicable DTC. Refer to Diagnostic Aids.
- 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 5-volt reference circuit one at a time while monitoring the scan tool 5 volt reference parameter. The voltage should remain within 4.8-5.2 volts.
Important: Additional DTCs will set when disconnecting the components.
| ⇒ | 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 control module. |
| ⇒ | If greater than the specified range, 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. |
Important: A short to voltage on the signal circuit of certain components may cause this DTC to set.
| ⇒ | If less than the specified range when a component is connected, replace the component. |
| ⇒ | If greater than the specified range when a component is connected, test the component signal circuit for a short to voltage. If all circuits test normal, replace the ECM. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Engine Control Module Replacement for ECM replacement, setup, and programming |
