For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle

• | Review Strategy Based Diagnosis

• | Diagnostic Procedure Instructions

### 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 located on the fuel line. The fuel pressure sensor monitors the fuel pressure in the fuel line. The fuel pump flow control module (FPCM) monitors the voltage signal from the fuel pressure sensor.

### Conditions for Running the DTC

The ignition is on.

### Conditions for Setting the DTC

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

### Action Taken When the DTC Sets

DTCs P0641 and P06A6 are Type A DTCs.

### Conditions for Clearing the DTC

DTCs P0641 and P06A6 are Type A 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

### Circuit/System Testing

1. Ignition OFF, disconnect harness connector of the B47 fuel pressure sensor.
2. Ignition OFF, test for less than 1.0 Ω between the low reference circuit terminal 2 and ground.

⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the K27 FPCM.

3. Ignition ON, test for 4.8-5.2 V between the 5 V reference circuit terminal 3 and ground.

⇒ | If less than the specified range, test the 5 V reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K27 FPCM.

⇒ | If greater than the specified range, test the 5 V reference circuit for a short to voltage. If the circuit tests normal, replace the K27 FPCM.

4. If all circuits test normal, replace the B47 fuel pressure sensor.

### Repair Instructions

Perform the Diagnostic Repair Verification

• | Fuel Pressure Sensor Replacement Fuel Injection Fuel Rail Fuel Pressure Sensor Replacement

• | Control Module References