Fault code P0091 – a step-by-step guide to diagnosing and fixing it

Error code P0091 is displayed and the check engine light is on - what does this mean?

With this DTC, the OBD system detects a fault in the fuel pressure control valve control circuit 1, which is classified as too low. The trouble code P0091 indicates a problem with the fuel pressure control, which can impair engine performance. For various manufacturers, this fault code may also be referred to as "Fuel Pressure Regulator 1 Control Circuit Low".

What can cause this fault code?

• Defective fuel pressure regulator valve
• Damaged wiring to the pressure regulator valve
• Corroded or loose plug connections
• Defective fuel pump
• Clogged fuel filter
• Faulty engine control unit (ECU)
• Short circuit in the electrical circuit
• Defective fuel pressure sensor

What symptoms occur in parallel with fault code P0091?

• Starting problems: The vehicle is difficult to start or does not start at all
• Loss of power: Noticeable drop in engine power, especially under load
• Uneven idling: Engine runs unevenly at idle speed
• Jerking when accelerating: Vehicle does not pull away smoothly
• Increased fuel consumption: Significantly higher fuel consumption than usual
• Stalling of the engine: Engine stalls while driving

How can the problem with error code P0091 be rectified?

• The repair requires a systematic approach to identify the exact cause.
• Replace the fuel pressure control valve if electrical tests confirm an internal defect
• Check the wiring and plug connections to the pressure control valve and replace if damaged
• Replace the fuel filter if it is clogged and affects the system pressure
• Replace fuel pump if pressure tests show insufficient delivery rate
• Check engine control unit and reprogram or replace if necessary
• Replace fuel pressure sensor if it is transmitting incorrect values to the control unit
• Test the entire electrical circuit of the fuel system for short circuits and interruptions