P0191 — Fuel Rail Pressure Sensor Circuit Range / Performance
The fuel rail pressure sensor signal is within electrical limits but doesn't match commanded rail pressure under various engine loads. Common in common-rail diesel and GDI petrol engines.
General code reference. Confirm the definition and diagnostic procedure for your vehicle's year, model and engine. A stored code alone does not identify a failed part.
Affected components
- Fuel rail pressure sensor
- High pressure pump
- Rail pressure regulator
Possible causes to check
These are possible checks, not a ranked diagnosis. Follow the vehicle manufacturer's test procedure before replacing parts.
- Pressure sensor drifted
- Pressure regulator stuck
- High-pressure pump worn
Diagnostic notes
- The malfunction indicator lamp may illuminate
- This code can affect emissions
- A drive cycle may be required after repair
Sources
Check each reference's vehicle and model-year scope. General background links do not establish which fault is most likely on your vehicle.
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.