P0191
DTC P0191
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 (FRP) Sensor Performance
Diagnostic Fault Information
Typical Scan Tool Data
Circuit/System Description
The fuel rail pressure (FRP) sensor has a 5-volt reference circuit, a signal circuit, and a low reference circuit. The engine control module (ECM) monitors the voltage on the FRP sensor circuits. When the fuel pressure is high, the signal voltage is high. When the fuel pressure is low, the signal voltage is low. The fuel pressure regulator has a solenoid supply voltage circuit and a solenoid control circuit. The ECM controls the fuel pressure regulator, which regulates high pressure fuel that goes to the fuel injector rails and the injectors.
Conditions for Running the DTC
* DTCs P0016, P062F, P0116, P0117, P0118, P0192, P0193, P0652 or P0653 are not set.
* The ignition is ON, with the engine OFF for 30 seconds.
* The coolant temperature has dropped more than 5°C (9°F) since Last Key Cycle.
* The FRP sensor voltage is between 352-650 volts.
OR
* The ignition has been off less than 70 seconds.
* The fuel temperature is more than 60°C (140°F).
* The FRP sensor voltage is between 352-650 volts.
* This diagnostic runs continuously within the above conditions.
Conditions for Setting the DTC
* The FRP sensor is below 0.352 volt or above 0.650 volt when the ignition is ON and the engine is OFF.
OR
* The FRP sensor is below 0.352 volt or above 0.650 volt within 70 seconds of the ignition being turned OFF.
Action Taken When the DTC Sets
DTC P0191 is a Type A DTC.
Conditions for Clearing the MIL/DTC
DTC P0191 is a Type A DTC.
Circuit/System Verification
Important:
* You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.
* If you cannot duplicate the condition, operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
1. Verify that DTCs P0652 or P0653 are not set.
• If any of the DTCs are set, Refer to Diagnostic Trouble Code (DTC) List - Vehicle. Diagnostic Trouble Code Descriptions
2. Observe the Fuel Rail Pressure Sensor parameter with a scan tool. During engine cranking, the pressure should be at least 10 MPa. With the engine running at idle, the pressure should be close to the Desired Fuel Rail Pressure. As the engine speed increases, the Desired Fuel Rail Pressure and the Actual Fuel Rail Pressure should closely match each other.
3. Engine running, observe the DTC information with a scan tool. DTC P0191 should not set.
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame Records data.
Circuit/System Testing
Important: Fuel pressure control will be disable if DTC P0087, P0088, P0192, or P0193 are set. Codes must be cleared to enable the device control.
1. Turn OFF the ignition.
2. Disconnect the ECM connector and the fuel pressure regulator connector.
3. Test the fuel pressure regulator solenoid supply voltage circuit for a short to voltage.
4. Disconnect the FRP sensor.
5. Test the FRP signal circuit, the 5-volt reference circuit, and the low reference circuit for high resistance.
• If all circuits test normal, replace the FRP sensor.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
* Fuel Injection Fuel Rail Fuel Pressure Sensor Replacement
* Control Module References for ECM replacement, programing and setup Programming and Relearning Verification Tests