Error Code P0191
Moderate Issue
DTC Code P0191 indicates a Fuel Rail Pressure Sensor Circuit Range/Performance issue. This code is triggered when the Powertrain Control Module (PCM) detects that the Fuel Rail Pressure (FRP) sensor's output is not within the expected range, affecting the fuel delivery system's performance.
What symptoms indicate Error Code P0191?
- Engine Light ON: The check engine light or service engine soon warning light illuminates, indicating an issue with the fuel rail pressure sensor circuit. This can be linked to potential causes such as a faulty fuel rail pressure sensor, wiring issues, or a malfunctioning fuel pump.
- Engine Will Not Start: The engine may fail to start due to incorrect fuel pressure readings. This symptom can be associated with potential causes like a defective fuel rail pressure sensor, fuel delivery problems, or electrical issues within the sensor circuit.
What causes OBD code Error Code P0191?
- Low or no fuel can lead to insufficient pressure in the fuel rail, triggering the sensor to detect an anomaly.
- A faulty Rail Pressure (FRP) Sensor may provide incorrect readings, causing the ECU to register a performance issue.
- An open or shorted FRP harness can disrupt the signal transmission, leading to inaccurate pressure readings.
- Poor electrical connections in the FRP circuit can result in intermittent or faulty sensor signals.
- A faulty fuel pump may not deliver adequate pressure, affecting the fuel rail's performance and triggering the error code.
How to fix OBD code Error Code P0191?
- Initial Inspection: Inspect the fuel rail pressure sensor and its wiring for any visible damage or disconnections. Ensure all connectors are secure and free from corrosion.
- Check Fuel Pressure: Use a fuel pressure gauge to measure the actual fuel pressure in the rail. Compare the readings with the manufacturer's specifications to determine if the pressure is within the acceptable range.
- Sensor Voltage Test: With a multimeter, check the voltage at the fuel rail pressure sensor connector. Verify that the voltage is within the specified range as per the vehicle's service manual.
- Inspect Fuel Pump: Examine the fuel pump for proper operation. A malfunctioning fuel pump can cause incorrect fuel pressure readings, leading to a P0191 code.
- ECM/PCM Check: Ensure the Engine Control Module (ECM) or Powertrain Control Module (PCM) is functioning correctly. Faulty modules can misinterpret sensor data, triggering the code.
- Review Related Codes: Investigate any related codes (P0190, P0192, P0193, P0194) that may provide additional context or indicate a broader issue with the fuel system.