OBD CodesWhat it means
Fuel is held at pressure in a pipe called the rail, ready for the injectors. On direct-injection petrol engines and all modern diesels the pressure is very high. These codes mean the pressure is not what the computer asked for, or the sensor that measures it cannot be trusted.
Codes in this group
| Code | Meaning |
|---|---|
| P0087 | Fuel rail pressure too low |
| P0088 | Fuel rail pressure too high |
| P0190 | Fuel rail pressure sensor circuit fault |
| P0191 | Fuel rail pressure reading out of range |
| P0192 | Fuel rail pressure sensor signal low |
| P0193 | Fuel rail pressure sensor signal high |
| P0194 | Fuel rail pressure sensor signal cuts in and out |
Bank 1 is the side of the engine that has cylinder 1. Sensor 1 is before the catalytic converter and sensor 2 is after it. More terms explained.
What you may notice
- Loss of power, most of all under load or uphill
- Engine cuts out or will not start
- Long cranking before starting
- Limp mode
Common causes
Most likely first:
- A blocked fuel filter (very common on diesels)
- A weak low-pressure or high-pressure fuel pump
- A faulty pressure regulator or control valve
- A failed rail pressure sensor or its wiring
- Running the tank very low or contaminated fuel
What to check first
- Check when the fuel filter was last changed
- Do not keep driving a diesel that loses power with this code: a failing pump can send metal through the whole fuel system
- Never loosen high-pressure fuel pipes yourself: the pressure can cause serious injury
Have a mechanic confirm. A fault code tells you which system reported a problem, not which part has failed. The same code can have several causes, and they differ between car models. Use this page to understand the code, then have a qualified mechanic test the car before any part is replaced.
After the repair
Once the cause is fixed, the code can be cleared with a scan tool, or the warning light goes out by itself after several trips without the fault. Clearing a code without fixing the cause only hides it for a while. More about clearing codes.
Related codes
Mass air flow (MAF) sensor (P0100), Manifold pressure (MAP) and barometric sensor (P0105), Intake air temperature sensor (P0110), Engine coolant temperature sensor (P0115), Thermostat and engine warm-up (P0125), Throttle position sensor (P0120), Accelerator pedal sensor and throttle agreement (P2120), Electronic throttle actuator (P2100). All codes.
Written in November 2026. These are generic OBD-II codes, the same on all makes. Causes and repair steps differ between models.