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DTC P0191 (LF1, LFW)

DTC P0191 (LF1, LFW)

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 Descriptor

DTC P0191

Fuel Rail Pressure Sensor Performance

Diagnostic Fault Information

Circuit Short to Ground Open/High Resistance Short to Voltage Signal Performance
5 V Reference Voltage P0192, P0193, P0340, P0345, P0365, P0390, P0506, P0641, P2227, P2229 P0192 P0193, P0641, P2227, P2229 P0191
Fuel Rail Pressure Sensor Signal P0192 P0192, P0193 P0193 P0191
Low Reference - P0193 P0193 P0191


Circuit/System Description

The fuel rail pressure sensor detects fuel pressure within the fuel rail. The engine control module (ECM) provides a 5 V reference voltage on the 5 V reference circuit and ground on the low reference circuit. The ECM receives a varying signal voltage on the signal circuit. The ECM monitors the voltage on the fuel rail pressure sensor circuits. When the fuel pressure is high, the signal voltage is high. When the fuel pressure is low, the signal voltage is low.

Conditions for Running the DTC


Condition 1

• The engine speed is greater than 25 RPM for greater than 31 s.

• DTC P0191 runs once an ignition cycle at engine start up when the condition has been met.



Condition 2 and 3

• The engine speed is greater than 25 RPM for greater than 30 s.

• The engine coolant temperature (ECT) at the previous engine shut down was warmer than 72°C (162°F).

• The ECT at engine start is colder than 55°C (131°F).

• At engine start, if the ECT is warmer than the intake air temperature (IAT), then the IAT must be within 35°C (95°F) of the ECT.

• At engine start, if the IAT is warmer than the ECT, then the ECT must be within 10°C (50°F) of the IAT.

• The block heater, if equipped, is not active.

• The engine off time since the previous engine shut down is greater than 4.2 h.

• DTC P0191 runs once an ignition cycle at engine start up when the above conditions have been met.


Conditions for Setting the DTC

Condition 1

DTC P0087, P2187, or P2188 is set, and the fuel pressure at ignition ON is less than 120 kPa (17.4 psi) for greater than 4 s or for a cumulative of 30 s.

Condition 2

DTC P0088, P2177, or P2187 is set, and the fuel pressure at ignition ON is greater than 1.5 MPa (218 psi) for greater than 4 s or for a cumulative of 30 s.

Condition 3

The fuel pressure at ignition ON is greater than 1.5 MPa (218 psi) and a fuel pressure increase of greater than 385 kPa (56 psi) occurs during the fuel pump prime. The condition exists for greater than 4 s or for a cumulative of 30 s.

Action Taken When the DTC Sets


• DTC P0191 is a Type A DTC.

• A message center or an indicator may display Reduced Engine Power.


Conditions for Clearing the DTC

DTC P0191 is a Type A DTC.

Diagnostic Aids

A condition with the fuel tank fuel pump module or the fuel pump control module may set this DTC.

Reference Information

Schematic Reference

Engine Controls Schematics (3.0L (LF1)) Engine Controls Schematics (2.8L (LAU))

Connector End View Reference

Component Connector End Views

Description and Operation

Fuel System Description (LF1) Fuel System Description (LAU or LY7)

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 Verification


1. Observe the scan tool DTC information, verify DTC P0627, P0628, P0629, P069E or U0109 is not set.

2. If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .

3. Engine idling, observe the scan tool Fuel Rail Pressure Sensor parameter. The pressure should be approximately 1.9-5.0 Mpa (276-725 psi).

4. Engine idling, the scan tool Fuel Rail Pressure Sensor should be close to the scan tool Desired Fuel Rail Pressure. As the engine speed increases, the Desired Fuel Rail Pressure and the Fuel Rail Pressure Sensor should closely match each other.

5. Move related harnesses/connectors of the B47B fuel rail pressure sensor and verify the engine does not stumble, stall, or change engine speed.

6. If the engine stumbles, stalls, or changes engine speed, test or repair the suspected harness or connection.

7. Observe the DTC information with a scan tool, DTC P0191 should not set.

8. 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


1. Ignition OFF, disconnect the B47B fuel rail pressure sensor connector.

2. Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 5 Ω between the low reference circuit terminal C 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 K20 ECM.

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

5. 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 K20 ECM.

6. If greater than the specified range, test the 5 V reference circuit for a short to voltage. If the circuit tests normal, replace the K20 ECM.

7. Ignition ON, verify the scan tool Fuel Rail Pressure Sensor voltage parameter is less than 0.02 V.

8. If greater than the specified value, test the signal circuit for a short to voltage. If the circuit tests normal, replace the K20 ECM.

9. Connect a 3 A fused jumper wire between the signal circuit terminal B and the 5 V reference circuit terminal A. Verify the scan tool Fuel Rail Pressure Sensor Voltage parameter is greater than 4.96 V.

10. If less than the specified value, test the signal circuit for an open/high resistance or a short to ground. If the circuit tests normal, replace the K20 ECM.

11. If all circuits test normal, replace the B47B fuel rail pressure sensor.


Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.


• Fuel Pressure Sensor Replacement - Fuel Injection Fuel Rail

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