Powertrain Management (ECM, with Supercharger)

DTC P0641 or P0651 (ECM, with Supercharger)

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.

* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC P0641
- 5 V Reference 1 Circuit

DTC P0651
- 5 V Reference 2 Circuit

Circuit/System Description

The engine control module (ECM) has 2 internal 5 V reference circuits. Each internal reference circuit provides a 5 V reference for more than one sensor. A short to ground or short to voltage on one of the external 5 V reference circuits can affect all the components connected to the same internal 5 V reference circuit.

Conditions for Running the DTC

* Reduced Engine Power is not active.

* The ignition is ON.

* The ignition voltage is greater than 6 V.

* 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 V reference 1 or 2 circuit for greater than 0.5 s.

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

DTC P0641

The 5 V reference 1 circuit provides 5 V to the sensors listed below:

* Fuel tank pressure sensor

* Barometric pressure (BARO) sensor, throttle inlet absolute pressure sensor

* Supercharger air inlet pressure sensor

* Manifold absolute pressure (MAP) sensor, supercharger air outlet pressure sensor

* Accelerator pedal position (APP) sensor 2

* Engine oil pressure sensor

* Air conditioning (A/C) refrigerant pressure sensor

* Camshaft position sensor

DTC P0651

The 5 V reference 2 circuit provides 5 V to the sensors listed below:

* APP sensor 1

* Throttle position sensor 1 and 2

* Crankshaft position sensor

* Clutch pedal position sensor, if equipped

It may be possible to locate the fault by disconnecting one component at a time from the affected 5 V reference circuit while viewing the 5 V Reference Circuit Status parameter on the scan tool. The scan tool parameter will change from Malfunction to OK when the source of the fault is disconnected. If all 5 V reference components have been disconnected and a fault is still indicated, the fault may exist in the wiring harness.

Reference Information

Schematic Reference

Engine Controls Schematics (L99/LS3) [1][2]Electrical DiagramsEngine Controls Schematics (LSA) [1][2]Electrical Diagrams

Connector End View Reference

Component Connector End Views Fuel Pump and Level Sensor Assembly - Primary

Electrical Information Reference

* Circuit Testing Circuit Testing

* Connector Repairs Connector Repairs

* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections

* Wiring Repairs Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References Control Module References for scan tool information

Circuit/System Verification

1. Observe the scan tool 5 V reference 1 circuit status and the 5 V reference 2 circuit status parameters. Verify the parameters display OK.

2. Ignition ON, observe the DTC information with a scan tool. DTCs P0641 and P0651 should not set.

3. 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

Note: Additional DTCs will set when disconnecting the components.

1. Ignition OFF, disconnect the harness connector of all the sensors for the applicable DTC. Refer to Diagnostic Aids for the appropriate sensors.

2. Ignition ON, measure for 4.8-5.2 V between one of the 5 V reference circuits and ground.

• If less than the specified range, test for a short to ground on the 5 V reference circuit for each affected component. If all circuits test normal, replace the K20 engine control module.

• If greater than the specified range, test for a short to voltage on the 5 V reference circuit for each affected component. If all circuits test normal, replace the K20 engine control module.

Note: A short to voltage on the signal circuit of certain components may cause this DTC to set.

3. Connect each component associated with the 5 V reference circuit, one at a time, while monitoring the appropriate scan tool 5 V Reference Voltage parameter. Verify the voltage remains between 4.8-5.2 V.

• If not within the specified range when a component is connected, test the signal circuit for a short to voltage. If the circuit tests normal, replace the appropriate component.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.

* Accelerator Pedal Position Sensor Replacement Service and Repair

* Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement (LFX) Service and RepairAir Conditioning (A/C) Refrigerant Pressure Sensor Replacement (LSA, LS3, L99) Service and Repair

* Barometric Pressure Sensor Replacement (LSA) Service and Repair

* Camshaft Position Sensor Replacement (Without Actuator) Camshaft Position Sensor Replacement (Without Actuator)Camshaft Position Sensor Replacement (With Actuator) Camshaft Position Sensor Replacement (With Actuator)

* Clutch Pedal Position Sensor Replacement Service and Repair

* Crankshaft Position Sensor Replacement Service and Repair

* Engine Oil Pressure Sensor and/or Switch Replacement (L99/LS3) Service and RepairEngine Oil Pressure Sensor and/or Switch Replacement (LSA) Service and Repair

* Fuel Tank Pressure Sensor Replacement Service and Repair

* Supercharger Air Inlet Pressure Sensor Replacement Supercharger Air Inlet Pressure Sensor Replacement

* Supercharger Air Outlet Pressure Sensor Replacement Supercharger Air Outlet Pressure Sensor Replacement

* Throttle Body Assembly Replacement (L99 or LS3) Removal and ReplacementThrottle Body Assembly Replacement (LSA) Removal and Replacement

* Control Module References Control Module References for ECM replacement, setup, and programming