P0091 code definition

Fuel Pressure Regulator 1 Control Circuit Low

What the P0091 code means

P0091 means that the Powertrain Control Module (PCM) has detected fuel pressure that is outside the specification set by the manufacturer.

What are the causes of the P0091 code?

  • Faulty fuel pump
  • Faulty fuel pump relay
  • Faulty PCM
  • Faulty electric fuel pressure regulator
  • Restriction in the fuel filter or other parts of the fuel system
  • Damaged wiring such as a short to ground
  • Fuel tank low on fuel

What are the symptoms of the P0091 code?

  • No start or rough start condition
  • Stalling during acceleration
  • Lack of power
  • Poor fuel economy

In some cases, the engine may start but the starter may need to crank longer in order to achieve this. It is also possible that other trouble codes will accompany P0091

How does a mechanic diagnose the P0091 code?

A mechanic may start with a good visual inspection of the fuel system, including:

  • Fuel tank
  • Fuel pump
  • Fuel filter
  • Lines and hoses
  • Electrical wiring
  • Electrical connectors
  • Sensors
  • Injectors

There may be other parts of your vehicle's fuel system not listed here that are specific to your particular vehicle.

During a through inspection, the mechanic will note any obvious damages to the system and repair them before proceeding with the diagnosis.

After the visual inspection has been performed, the mechanic will perform a fuel pressure test to test the functionality of all fuel system sensors.

Common mistakes when diagnosing the P0091 code.

A common mistake when diagnosing the P0091 code would be replacing the fuel pressure regulator or fuel pump without knowing for sure they are bad.

Sometimes, mechanics will see a trouble code and take that for what is actually wrong with the car. A trouble code is simply a sensor giving a reading that the Powertrain Control Module sees as out of specification. Just because a particular part is mentioned in a trouble code, it does not mean that the part is faulty.

How serious is the P0091 code?

The P0091 code can be very serious as it affects the way the engine runs and could potentially stop the engine from starting; it could likely leave a driver stranded on the side of the road. It would behoove the driver of a vehicle with this code stored to have this issue diagnosed and repaired as soon as possible in order to prevent the possibility of a break down.

What repairs can fix the P0091 code?

Additional comments regarding the P0091 code.

  • It is very important to take other codes stored with the P0091 code into consideration during diagnosis, as the P0091 code by itself may mean something different than if it were accompanied by other diagnostic trouble codes.

Need help with a P0091 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

This article originally appeared on YourMechanic.com as P0091 OBD-II Trouble Code: Fuel Pressure Regulator 1 Control Circuit Low and was authored by Andrew Quinn.


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