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 provides an overview of each of the diagnostic category. |
DTC Descriptors
DTC P0641: 5V Reference 1 CircuitDTC P0651: 5V Reference 2 Circuit
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Accelerator Pedal Position (APP) Sensor 1 5V Reference 2 Circuit | P0651, P2122 | P2122 | P0651, P2123 | -- |
Accelerator Pedal Position (APP) Sensor 2 5V Reference 1 Circuit | P0641, P2127 | P2127 | P0641, P2128 | -- |
Air Conditioning (A/C) Refrigerant Pressure Sensor 5V Reference 1 Circuit | P0641 | P0532 | P0641 | -- |
Crankshaft Position Sensor 5V Reference 2 Circuit | P0651 | P0335 | P0651 | -- |
Exhaust Camshaft Position Sensor 5V Reference 1 Circuit | P0641, P0365 | P0365 | P0641, P0365 | -- |
Intake Camshaft Position Sensor 5V Reference 1 Circuit | P0641, P0340 | P0340 | P0641, P0340 | -- |
Manifold Absolute Pressure (MAP) Sensor 5V Reference 1 Circuit | P0641, P0107 | P0107 | P0641, P0107 | -- |
Throttle Position (TP) Sensor 1 5V Reference 2 Circuit | P0651, P0122 | P0122 | P0651, P0123 | -- |
Throttle Position (TP) Sensor 2 5V Reference 2 Circuit | P0651, P0222 | P0222 | P0651, P0223 | -- |
Circuit/System Description
The engine control module (ECM) has 2 internal 5V reference busses called 5V reference 1 and 5V reference 2. Each reference buss provides 5V reference circuits for more than one sensor. A fault condition on one 5V reference circuit will affect the other 5V reference circuits connected to that reference buss. The ECM monitors the voltage on the 5V reference buss.
The 5V reference 1 buss provides 5V to the following sensors:
| • | The manifold absolute pressure (MAP) sensor |
| • | The air conditioning (A/C) refrigerant pressure sensor |
| • | The accelerator pedal position (APP) sensor 2 |
| • | The exhaust camshaft position (CMP) sensor |
| • | The intake CMP sensor |
The 5V reference 2 buss provides 5V 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, and P2610 are not set. |
| • | The ignition is in Unlock, Accessory, Run, or Crank. |
| • | The ignition voltage is more than 5.23V. |
| • | DTCs P0641 and P0651 run continuously when the above conditions are met. |
Conditions for Setting the DTC
The ECM detects a voltage out of range condition on the 5V reference 1 or 2 buss 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.
Diagnostic Aids
It may be possible to locate the fault by disconnecting one component at a time from the 5V reference circuit while viewing the 5V Reference circuit parameter on the scan tool. The scan tool parameter would change from Fault to OK when the source of the fault is disconnected.
If all 5V reference components have been disconnected and a Fault is still indicated, the fault may exist in the wiring harness.
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
- With the ignition ON and the engine OFF, observe the 5V Reference 1 and 2 parameters. The scan tool should display 4.8-5.2V for a normally operating system.
- Ignition ON, observe the DTC information with a scan tool. DTCs P0641 and P0651 should not set on this ignition cycle.
- Operate the vehicle within the Conditions for Running the DTC. 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 of all appropriate sensors for the applicable DTC.
- Ignition ON, measure for 4.8-5.2V between one of the 5V reference circuits and ground.
- Connect each component associated with the 5V reference circuit, one at a time, while monitoring the voltage. Verify the voltage remains between 4.8-5.2V.
Note: A short to voltage on the signal circuit of certain components may cause this DTC to set.
| ⇒ | If the voltage is less than the specified value, test for a short to ground on all the 5V reference circuits. If all circuits test normal, replace the K20 ECM. |
| ⇒ | If the voltage is greater than the specified value, test for a short to voltage on all the 5V reference circuits. If all circuits test normal, replace the K20 ECM. |
| ⇒ | If the voltage display is not within the specified range when a component is connected, test the signal circuit for a short to voltage. If all circuits test normal, replace the component. |
Repair Instructions
| • | Control Module References for ECM replacement, setup, and programming |
Repair Verification
With the ignition ON and the engine OFF, observe the 5V Reference 1 and 2 parameters. The scan tool should display 4.8-5.2V for a normally operating system.
