GM Service Manual Online
For 1990-2009 cars only

DTC P0641 or P06A6 FPCM

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 diagnostic category.

DTC Descriptors

DTC P0641: 5-Volt Reference Circuit

DTC P06A6: 5-Volt Reference Performance

Diagnostic Fault Information

Circuit

Short to Ground

Open or High Resistance

Short to Voltage

Signal Performance

5-Volt Reference

P0641

P0641, P06A6

P0641

P06A6

Fuel Rail Pressure (FRP) Sensor Signal

P0192

P0191, P0192

P0193

P0191

Fuel Line Pressure Sensor Low Reference

--

P0641, P06A6

--

P06A6

Circuit/System Description

The fuel pressure sensor is mounted on the fuel line. Fuel pressure is measured by the fuel pressure sensor. The fuel pump flow control module (FPCM) monitors the voltage signal from the fuel pressure sensor and also supplies the voltage and the ground of the fuel pressure sensor.

Conditions for Running the DTC

The ignition is on.

Conditions for Setting the DTC

The FPCM detects that the fuel rail pressure (FRP) 5-volt reference is above or below a predetermined voltage threshold.

Action Taken When the DTC Sets

DTC P0641 and P06A6 are A type DTCs.

Conditions for Clearing the DTC

DTC P0641 and P06A6 are A type DTCs.

Diagnostic Aids

Using the Failure Records data may help locate an intermittent condition. If you cannot duplicate the DTC, the information in the Failure Records can help determine how many miles since the DTC set. The Fail Counter and Pass Counter can help determine how many ignition cycles that the diagnostic test reported a pass and/or a fail.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Fuel System Description

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the fuel line pressure sensor.
  2. Ignition OFF, test for less than 1.0 ohm between the low reference circuit terminal 2 and ground.
  3. If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the FPCM.
  4. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 3 and ground.
  5. If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the FPCM.
    If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the FPCM.
  6. If all circuits test normal, replace the fuel pressure sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Fuel Tank Pressure Sensor Replacement
    •  Control Module References for FPCM replacement, setup, and programming