Fault code P0191 – a step-by-step guide to diagnosing and fixing it

Error code P0191 is displayed and the check engine light is on - what does this mean?

DTC P0191 is recognized by the OBD/EOBD system when there is a problem with the fuel rail pressure sensor (FRP sensor). This trouble code indicates that the ECU is receiving a signal outside the expected range from the fuel rail pressure sensor. Different manufacturers may have slightly different names for this trouble code, but it always refers to the fuel pressure sensor in the rail system.

What causes can this error code have?

• Defective fuel rail pressure sensor (FRP sensor)
• Damaged or corroded cable connections to the sensor
• Loose or defective plug connections on the pressure sensor
• Short circuit or interruption in the sensor wiring
• Defective fuel pump with irregular pressure
• Clogged fuel filter
• Leaks in the fuel rail system
• Faulty engine control unit (ECU)
• Defective fuel pressure regulator

What symptoms occur in parallel with fault code P0191?

• Starting problems: The vehicle is difficult to start or does not start at all. Uneven idling: The engine runs unevenly and jerks when idling. Loss of power: Significantly reduced engine power, especially under load or when accelerating. Increased fuel consumption: Consumption increases noticeably due to the disrupted fuel supply. Engine misfiring: Jerking and misfiring while driving, especially at higher engine speeds. Exhaust problems: Black smoke from the exhaust or increased emission values.

How to fix the problem of fault code P0191?

• Repairing the P0191 fault code requires a systematic diagnosis of the fuel pressure system.
• Replace the fuel rail pressure sensor: Remove the defective FRP sensor on the fuel rail and replace it with a new original part, replacing the seals in the process
• Repair sensor wiring: Locate damaged cables to the pressure sensor and replace with new cables, check all connections for tightness
• Clean and secure plug connections: Clean corroded or loose plugs on the sensor, treat with contact spray and connect firmly
• Replace fuel filter: Replace clogged fuel filter with new filter to ensure even fuel pressure
• Check and replace the fuel pump: Measure fuel pump pressure and replace the complete pump unit in the tank if there are deviations
• Check fuel rail system for leaks: Check all connections, lines and the rail itself for leaks and replace defective parts