P0191
Fuel Rail Pressure Sensor Circuit Range/Performance
- Severity
- High
- Driving
- Drive only to a garage
The fuel rail pressure reading is within its valid electrical range but does not match what the module commanded. This is the code that most often turns out to be true rather than a sensor fault: the pressure really is wrong, because the filter is blocked, the pump is worn, or the injectors are returning more fuel than they inject.
Possible causes
- CommonFailed fuel rail pressure sensor
- CommonCorroded or damaged connector at the sensor
- CommonWiring fault between the sensor and the module
- CommonGenuine fuel supply problem - blocked filter, weak pump, air in the system - that the sensor is correctly reporting
- PossibleFuel pressure regulator or metering valve fault
- PossibleWorn high pressure pump
What you might notice
- Hard starting, or refusing to start at all
- Loss of power, or dropping into limp mode
- Rough running, misfiring, or cutting out
- Smoke from the exhaust
- Check engine light on
What to check, in order
- Read all codes before deciding this is the sensor. Fuel delivery and pressure regulation codes stored alongside usually mean the sensor is telling the truth about a supply problem, and replacing it would fix nothing.
- Compare commanded rail pressure against actual on live data, at idle and under load. A system that holds pressure at idle and loses it under load is worn rather than broken.
- Check the low pressure supply and the filter first. Most rail pressure faults start upstream, and the filter is the cheapest thing in the chain.
- Inspect the sensor connector for corrosion and for damaged pins.
- Carry out an injector leak-off test before condemning the pump. Worn injectors bleed the rail down and produce exactly this, and injectors are far cheaper to test than a pump is to replace.
Read this code from your own car
Plug an ELM327 adapter into the OBD-II port under the dashboard. Pin16 reads every stored, pending and permanent code, explains each one like this page does — offline, with no account — and shows what the car recorded when the fault was set.
Where this code sits
P00xxP01xxP02xxP03xxP04xxP05xxP06xxP07xxP08xxP09xxP0AxxP0BxxP0CxxP0DxxP0ExxP0FxxP10xxP11xxP12xxP13xxP14xxP15xxP16xxP17xxP18xxP19xxP1AxxP1BxxP1CxxP1DxxP1ExxP1FxxP20xxP21xxP22xxP23xxP24xxP25xxP26xxP27xxP28xxP29xxP2AxxP2BxxP2CxxP2DxxP2ExxP2FxxP30xxP31xxP32xxP33xxP34xxP35xxP36xxP37xxP38xxP39xxP3AxxP3BxxP3CxxP3DxxP3ExxP3Fxx
Fuel and air metering
P0100P0101P0102P0103P0104P0105P0106P0107P0108P0109P0110P0111P0112P0113P0114P0115P0116P0117P0118P0119P0120P0121P0122P0123P0124P0125P0126P0127P0128P0129P0130P0131P0132P0133P0134P0135P0136P0137P0138P0139P0140P0141P0142P0143P0144P0145P0146P0147P0148P0149P0150P0151P0152P0153P0154P0155P0156P0157P0158P0159P0160P0161P0162P0163P0164P0165P0166P0167P0168P0169P0170P0171P0172P0173P0174P0175P0176P0177P0178P0179P0180P0181P0182P0183P0184P0185P0186P0187P0188P0189P0190P0191P0192P0193P0194P0195P0196P0197P0198P0199