What P0191 means
P means powertrain (engine and transmission). The 0 marks a generic code defined by SAE, so the same number means the same thing across makes. The third character, 1, places it in the fuel and air metering subsystem; the last two digits identify the specific fault.
The fuel rail pressure sensor reports pressure in the fuel rail. On direct-injection petrol and common-rail diesel engines it is critical: the engine computer controls the high-pressure pump from it and calculates injector opening time from it.
The letter "A" distinguishes between two or more of the same component on one vehicle. Which physical part is "A" is set by the manufacturer, so confirm it in the service information before replacing anything.
What “Range/Performance” means here
"Range/Performance" means the circuit is electrically intact — the signal sits inside its normal window — but the value does not make sense for the operating conditions. The module cross-checks it against what other inputs predict (a rationality test). That usually points at the fuel rail pressure sensor itself or the system it measures, rather than at the wiring.
What you may notice
Symptoms depend on the vehicle and on how the module responds to the fault. Any of these can accompany P0191:
- Hard starting or long cranking
- Hesitation, stalling or loss of power
- Reduced-power mode on some engines
Where to start diagnosing P0191
- Check the connector and the 5 V reference and ground at the sensor.
- Compare commanded and actual rail pressure in live data at idle and under load.
- With the engine off and the system relieved, the sensor should read near zero; a reading well above zero suggests a sensor or circuit fault.
- Treat high-pressure fuel systems with respect: follow the manufacturer's depressurising procedure before opening anything.
Clear the code only after recording freeze frame data: it shows the engine speed, load and temperature at the moment the fault set, which is often the best clue to reproducing it.
Live data to watch
These standard OBD2 values relate to P0191. Support varies by vehicle; a value your car does not report will simply be missing.
| Value | What to look for |
|---|---|
| Fuel rail pressure (PIDs 0x22/0x23) | Actual should track commanded with little lag. |
| Engine RPM (PID 0x0C) | Watch for stumbles coinciding with pressure dropouts. |
Related codes
Codes from the same fuel rail pressure sensor family. If several are stored together, the shared part — wiring, a common reference voltage, or the component itself — is the place to start.
Further reading
Frequently Asked Questions
What does P0191 mean?
P0191 is the generic SAE J2012 code for "Fuel Rail Pressure Sensor "A" Circuit Range/Performance". In plain terms, it means the engine computer has detected a "range/performance" fault on the fuel rail pressure sensor.
Can I keep driving with P0191?
Fuel pressure faults can cause stalling. Avoid driving where a sudden loss of power would be dangerous until it is checked.
What should I check first for P0191?
Check the connector and the 5 V reference and ground at the sensor.
Definition source: SAE J2012 / ISO 15031-6 generic DTC definitions. This is the generic meaning that applies across makes; a manufacturer can define a code more narrowly or add its own sub-codes, so confirm against the service information for your vehicle before replacing parts. Written by the OBDAssistant engineering team — see our editorial policy.