P0191Fuel Rail Pressure Sensor A Circuit Range/Performance
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- The rail pressure sensor A measures the pressure in the high-pressure fuel rail of common-rail diesels and petrol direct-injection engines; it is either a three-wire sensor (5 V reference, ground, signal rising with pressure, about 0.5 V at 0 bar) or a digital SENT sensor with two measuring channels. The engine module uses it as the feedback signal for rail pressure control. P0191 means the signal is electrically valid but not believable – stuck, offset or drifting. Manufacturers check it differently: Ford's 2023 diesels and GM's diesels test the offset with the system depressurised (Ford before starting after 10 min and 12 s after switch-off, window about 0.25–0.38 V; GM 6.5–14 % of supply); GM petrol direct injection compares the two SENT channels (limit 1.0 MPa); Saab's V6 diesel flags a large target deviation while the signal barely moves. GM treats it as a one-trip fault. Ford petrol direct injection uses P0087/P0088 instead. On a fault the module uses a substitute value and usually limits power.
- What you may notice
- Check engine light on
- Limp mode or 'Reduced Engine Power'
- Hard starting, stalling
- Rough running
- Likely causes
- LikelyRail pressure sensor drifting or stuck (wrong offset at 0 bar)
- PossibleGenuine pressure fault: high-pressure pump, pressure or volume control valve, tank pump
- PossibleConnector corroded, contact resistance in signal or ground
- RareFuel shortage or clogged filter
- RareControl module software
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €80 – €600
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.