P0091: Fuel pressure regulator control circuit low
The ECU sees a voltage that is too low in the fuel pressure regulator circuit. Usually a wire shorted to earth or a damaged connector.
| Code | P0091 |
|---|---|
| System | Engine and transmission |
| Group | P00xx, Air, fuel and emissions |
| Type | Generic: it means the same on every make |
| Can you keep driving? | With care |
What P0091 means
The ECU sends an electrical signal to the fuel pressure regulator and monitors the circuit voltage. If it sees it below what is possible, it stores this code. It is almost always electrical: a wire touching earth (body or engine), a damaged connector or the regulator coil itself.
Most common causes
- Chafed regulator wire touching earth
- Regulator connector with corrosion, moisture or bent pins
- Regulator coil shorted internally
- Wiring loom crushed or burnt near the engine
- Rarely, the ECU
Symptoms
- Engine warning light on
- Loss of power or limp mode
- Hard starting
- Jerking or the engine cutting out
Can you drive with P0091?
With care You can drive carefully to a garage, but the engine may lose power or stall. Do not leave it for long.
Open the bonnetthe in-depth explanation
How to check it
With the engine off, follow the wire to the regulator looking for chafing or burnt spots. If the code comes back as soon as you clear it, the fault is permanent and the garage will find it faster by testing the circuit.
How to read and clear P0091 with Final OBD
Plug an OBD2 scanner in under the steering wheel, switch the ignition on and open Final OBD. Under Faults you’ll see P0091 with its description and whether it’s confirmed, pending or permanent.
If the engine stores it over standard OBD, with FREE you read this code with its explanation for nothing and clear it. With PRO you also read the faults of every control unit and clear them in all of them.
Clearing the code only turns the light off: if the cause is still there, it comes back. Clear it once it’s fixed, and not right before an inspection. It’s all in how to read and clear fault codes and in inspections and OBD.
Similar codes
- P008D The fuel cooler pump control gives a lower signal than normal
- P008E The fuel cooler pump control gives a higher signal than normal
- P008F The engine coolant and fuel temperatures do not agree
- P0090 Fuel pressure regulator control circuit fault
- P0092 Fuel pressure regulator control circuit high
- P0093 Large leak detected in the fuel system
- P0094 A small leak has been detected in the fuel system
- P0095 The intake air temperature (bank 1, sensor 2) has an electrical fault
- P0010 Camshaft A actuator control: open circuit (bank 1)
- P0011 Camshaft A timing over-advanced (bank 1)
- P0012 Camshaft A timing over-retarded (bank 1)
- P0013 Camshaft B actuator control: open circuit (bank 1)
What does code P0091 mean?
The ECU sends an electrical signal to the fuel pressure regulator and monitors the circuit voltage. If it sees it below what is possible, it stores this code. It is almost always electrical: a wire touching earth (body or engine), a damaged connector or the regulator coil itself.
Can you drive with P0091?
You can drive carefully to a garage, but the engine may lose power or stall. Do not leave it for long.
How do you clear P0091?
With an OBD2 scanner and an app like Final OBD, which clears it for free if it’s stored by the engine control unit. But clearing it only turns the light off: if the cause isn’t fixed, P0091 comes back.
Read it on your car
Final OBD reads and clears engine faults through standard OBD for free, each one explained in plain English. With PRO it also reads the faults of every control unit, each make’s own codes included, and clears them in all of them.
