For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle

• | Review Strategy Based Diagnosis

• | Diagnostic Procedure Instructions

### DTC Descriptor

DTC P0191: Fuel Rail Pressure (FRP) Sensor 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 engine is running.

• | DTC P0192, P0193, P0231, P0232, P023F, P064A, P1255 or P06A6 are not active.

• | DTC P0641 has not failed this ignition cycle.

• | Fuel pump control is enabled and the fuel pump control state is normal.

• | The engine has been running for at least 5 seconds.

### Conditions for Setting the DTC

The FPCM does not detect a change in the fuel rail pressure (FRP) of at least 30 kPa (4.4 psi) when the fuel pump is operating at its minimum or maximum voltage limits for over 5 seconds.

### Action Taken When the DTC Sets

DTC P0191 is a Type A DTC.

### Conditions for Clearing the DTC

DTC P0191 is a Type A DTC.

### 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

#### 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

Important: Verify that the fuel tank is not empty. Only perform this diagnostic if there is at least 2 gallons of fuel in the fuel tank. Clear the DTC, and start and run the engine. Verify that the DTC P0191 resets before proceeding with the circuit system testing. If the DTC does not reset, refer to diagnostic aids.

1. Ignition OFF, disconnect the harness connector at the B47 fuel pressure sensor.
2. Ignition OFF, test for less than 1 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 fuel pump flow control module.

3. Ignition ON, test for 4.8-5.2 V between the B47 fuel pressure sensor 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 fuel pump flow control module.

⇒ | 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 fuel pump flow control module.

4. Verify the scan tool 5 V reference is less than 1 V.

⇒ | If greater than the specified range, test the signal circuit terminal 1 for a short to voltage. If the circuit tests normal, replace the K27 fuel pump flow control module.

5. Install a 3A fused jumper wire between the signal circuit terminal 1 and the 5 V reference circuit terminal 3. Verify the scan tool 5 V reference is greater than 4.8 V.

⇒ | If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K27 fuel pump flow control module.

6. 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