Fuel Rail/System Pressure - Too Low
On direct injection engines (common rail diesels and many petrol engines), fuel reaches the injectors at very high pressure from a shared pipe, the rail. A sensor measures that pressure and a regulator adjusts it. This code means rail pressure has dropped below the minimum.
What the car has detected
The engine computer has measured a rail fuel pressure below the minimum threshold for the engine's conditions.
With low pressure the engine may lose power, be slow to start or cut out while driving, which is dangerous on the road. Have it checked as soon as possible and avoid long trips.
Symptoms
- Engine warning light on
- Loss of power or limp mode
- Hard or long starting
- Hesitation or the engine cuts out while driving
Possible causes
- Clogged fuel filter or bent or squashed lines
- Weak low-pressure pump in the tank, or its strainer dirty
- Leaks on the high-pressure side or leaking injectors
- Rail pressure regulator sticking open or a worn high-pressure pump
- High-pressure pump out of time or wear of its cam and follower
- In cold weather, ice from water in the fuel at the tank pick-up strainer
Checks for the garage
- Read the other codes (for example pump timing ones) and the freeze frame data
- Compare actual and requested rail pressure in live data, at idle and when accelerating
- Command the pressure up and down with diagnostics and see whether the sensor follows
- Check power, earth and wiring of the regulator and the pressure sensor
- Measure the in-tank pump pressure with a gauge and check filter, lines and leaks
Next step
Make sure there is enough fuel and have the fuel filter, pump and possible leaks checked.
Go to a garage as soon as possible, especially if the engine pulls badly or has ever cut out. Pressure tests need diagnostics and a gauge.