P0091 code meaning
Fuel Pressure Regulator A Control Circuit Low
Powertrain system Generic code P00xx codes Check engine light
What P0091 means
On common-rail diesel and gasoline direct-injection engines, a high-pressure pump feeds the fuel rail, a sensor measures rail pressure, and the engine control module regulates it towards a target from its maps. The fuel pressure regulator A is the actuator the manufacturer designates for this: depending on the system a pressure control valve that releases fuel from the rail, or the control valve on the high-pressure pump. Some manufacturers report the pump valve under the "fuel volume regulator" codes instead. P0091 means the voltage in the control circuit is too low, typically a short to ground. Rail pressure can then no longer be controlled as intended, and the engine usually runs in reduced power.
P0091 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 2 hours
- Clears after repairAfter a drive cycle
Symptoms of P0091
- Check engine light on
- Reduced power mode
- Hard starting or stalling
Common causes of P0091
- Most likelyControl wire shorted to ground, or connector corroded
- Most likelyRegulator coil faulty
- PossibleFuse or supply voltage faulty
- Less likelyOutput driver in the engine control module faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Fuel pressure regulatorFuel pressure regulator wiringEngine control module
What each part of P0091 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 0 | Area: fuel and air metering and auxiliary emission controls. |
| 91 | The exact fault in that area. |
What to do next
- Note P0091 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0091
What does P0091 mean?
P0091 means "Fuel Pressure Regulator A Control Circuit Low". On common-rail diesel and gasoline direct-injection engines, a high-pressure pump feeds the fuel rail, a sensor measures rail pressure, and the engine control module regulates it towards a target from its maps. It is a generic code, so it means the same on every make.
Is it safe to drive with P0091?
Drive gently and only to a workshop. With P0091 the car can go into limp mode (reduced power) to protect itself.
Will P0091 fail an emissions test?
Yes, it can. P0091 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0091 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P0091 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.