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P0091 Code – What Does It Mean & How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.


P0091 is a special DTC with the title “Fuel Pressure Regulator’s 1 Control Channel Low.” This code shall be triggered by the detection of a low voltage signal in the fuel pressure regulator 1 control circuit by the engine control module.


In order to maintain optimum fuel pressure in the gasoline system, a fuel pressure regulator is of critical importance. The low voltage signal to the control circuit may lead to incorrect fuel pressure regulation, which can have a detrimental effect on engine performance and fuel efficiency.


  • A defective fuel pressure regulator may not be able to provide the ECM with the correct voltage signal, resulting in the P0091 error code.
  • Problems with the wire or connections: Signals to the ECM can be interfered with by frayed, corroded, or damaged wiring, connectors, or terminals connected to the fuel pressure regulator control circuit.
  • ECM Malfunction: The ECM itself may occasionally be at fault, leading to erroneous readings and the P0091 error code.


  • Check engine light: The illumination of check engine lights on the vehicle’s dashboard is the most obvious indication of the P0091 code. 
  • Poor engine performance: the vehicle may experience rough idle, hesitation during acceleration, or a lack of power. 
  • Lower fuel efficiency: If problems occur with the control circuit of the Pressure Regulator System, it can lead to an insufficient supply of fuel and result in a reduced fuel economy.


The P0091 error code must be diagnosed methodically:

  • OBD-II Scanner: A skilled mechanic will access the exact code and any associated codes recorded in the ECM using an OBD-II scanner.
  • Visual check: The fuel pressure regulator, along with any related wiring and connectors, will undergo a comprehensive visual check by the expert.
  • Verify Voltage and Ground: The mechanic will check the fuel pressure regulator control circuit’s voltage and ground signals using a multimeter.

Common mistakes

  •  Overlooking Wiring and Connector Issues: Sometimes, the root cause of the problem lies in damaged or loose wiring, which may be missed during the initial inspection. 
  • Neglecting related codes: In order to determine the true cause of the problem, other related codes may provide essential information.

How serious is this?

The P0091 code is very serious in terms of its actual causes and their effects on the fuel system and engine performance. If this is not addressed, it may lead to poor engine performance, reduced fuel efficiency, or possible harm to the rest of the components.

What repairs can fix the code?

repair manuals

  • Replace the Fuel Pressure Regulator: To guarantee correct fuel pressure regulation, the fuel pressure regulator should be changed if it is determined to be defective.
  • Repair or Replace Wiring and Connectors: To reestablish effective communication between the fuel pressure regulator and ECM, damaged or loose wiring and connectors should be fixed or replaced.
  • Examine and fix ECM problems: If an ECM fault is the source of the P0091 code, the ECM may need to be repaired or reprogrammed.

Related codes

  • P0088 (Fuel Rail/System Pressure – Too High): This code indicates high fuel pressure, which may be related to the P0091 issue.


The P0091 DTC code denotes a possible issue with the control circuit of the fuel pressure regulator, which may interfere with effective fuel pressure regulation in the fuel system. It’s critical to have the problem quickly diagnosed and fixed by a certified automobile mechanic if you see this code.

Maintaining engine performance, fuel efficiency, and the general health of your vehicle’s fuel system requires timely maintenance. Ignoring the issue might result in future difficulties that are more serious and more expensive to fix.

P0091 Code – What Does It Mean & How To Fix It