P0191: Fuel Rail Pressure Sensor "A" Circuit Range/Performance
The fuel rail pressure sensor reading is erratic or does not make sense for how the engine is running.
What P0191 means
The fuel rail pressure sensor tells the engine computer how much pressure the injectors are working with, which it needs to calculate how long to hold each injector open. RepairPal explains that P0191 means the sensor or its circuit is sending erratic readings that suggest an abnormal fuel pressure condition. The tricky part is that the problem can be the sensor or the actual fuel pressure. A sensor with a bad internal element or a corroded connector can produce jumpy readings, while a pump that cannot keep up or a regulator that sticks can make the real pressure jump around. RepairPal lists symptoms such as hesitation, stalling at stop signs, higher fuel use and lean or rich trim codes. Shops connect a mechanical gauge and compare it with the scan tool reading. If they match and both are unstable, they chase the fuel supply. If the gauge is steady but the sensor jumps, they test the wiring and replace the sensor.
Common symptoms
- Check engine light on
- Hesitation or stalling, especially at stops
- Higher fuel consumption
- Unusual exhaust smell
- Lean or rich codes like P0171 or P0172
Most common causes
- Faulty fuel rail pressure sensor
- Wiring or connector problem at the sensor
- Actual fuel pressure problem from a weak pump or bad regulator
- Clogged fuel filter
- Fuel leak on the high pressure side
What to check yourself first
Check the fuel rail pressure sensor connector for corrosion or a loose fit. Smell for raw fuel around the engine, which can point to a leak. Note whether lean or rich codes are set along with it.
Typical fixes and what they cost
| Fix | Typical cost | Note |
|---|---|---|
| Replace fuel pressure sensor | $422-$527 | When the sensor reading does not match a mechanical gauge. |
| Fuel pressure test | $60-$88 | Separates a sensor problem from a real pressure problem. |
| Electrical diagnosis to find a wiring or connector fault | $122-$179 | For corroded or loose sensor wiring. |
| Replace fuel pump | $1,344-$1,513 | If the pressure is truly unstable because the pump is failing. |
Typical US price ranges for parts and labor, not quotes. Your shop should confirm the cause with a diagnostic before replacing parts.
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Related codes
- P0087 Fuel Rail/System Pressure - Too Low
- P0171 System Too Lean (Bank 1)
- P0172 System Too Rich (Bank 1)
- P0230 Fuel Pump Primary Circuit
- P0300 Random/Multiple Cylinder Misfire Detected