Fuel & air metering · Powertrain · generic (SAE-defined)
P0191: Fuel Rail Pressure Sensor "A" Circuit Range/Performance
P0191 means the fuel rail pressure sensor reading does not match what the engine computer expects for current operating conditions, or it is behaving implausibly.
Standard title per SAE J2012 / ISO 15031-6 · Updated 2026-11-07 · By CarWhere Research
How P0191 sets
The fuel rail pressure (FRP) sensor reports fuel pressure in the rail to the powertrain control module (PCM), which uses it to control the fuel pump or high-pressure pump and to calculate injector timing. The PCM compares the sensor reading with the pressure it expects for the commanded conditions and checks how the signal changes. If the reading is out of range relative to expectations, stuck, or does not respond as pressure is commanded, P0191 sets. Values differ widely between port-injection, gasoline direct-injection and diesel systems and are manufacturer-specific.
Common causes of P0191
Roughly most likely first; the actual cause depends on the vehicle and needs testing to confirm.
- Failed fuel rail pressure sensor
- Actual fuel pressure problem from a weak low-pressure pump or clogged filter
- Faulty high-pressure fuel pump on direct-injection or diesel engines
- Wiring or connector fault in the sensor circuit
- Fuel pressure regulator or pressure control valve malfunction
- Running low on fuel or poor-quality fuel
P0191 symptoms
- Check engine light on
- Hard starting or long cranking
- Hesitation or stumbling under acceleration
- Stalling
- Reduced power or limp mode
- Rough idle
How P0191 is diagnosed
- Scan for codes and freeze frame; note related fuel pressure codes such as P0087 or P0088.
- Inspect the sensor connector and harness for damage or corrosion.
- Compare the sensor reading with key-on engine-off and running values in service information.
- Verify actual fuel pressure with a mechanical gauge where safe and appropriate for the system; high-pressure systems require proper procedures.
- Check sensor reference voltage, ground and signal circuits.
- If actual pressure is low, test the lift pump, filter and high-pressure pump.
Typical fixes for P0191
- Replace the fuel rail pressure sensor
- Repair sensor wiring or connector
- Replace a weak fuel pump or clogged fuel filter
- Replace the high-pressure fuel pump on direct-injection or diesel engines
- Replace a faulty pressure regulator or control valve
Replace parts only after testing confirms the cause — a code names the circuit or condition that failed a check, not necessarily the faulty part. We don’t publish per-repair prices; for what households actually spend on upkeep, see car repair costs.
Manufacturer notes
P0191 is commonly reported on diesel pickups and on gasoline direct-injection engines, where the rail sensor is sometimes integrated into the fuel rail; definitions can vary by manufacturer; check factory service information.
Related codes & warning lights
P0191 FAQ
What does code P0191 mean?
P0191 means the fuel rail pressure sensor reading does not match what the engine computer expects for current operating conditions, or it is behaving implausibly. The standard definition is "Fuel Rail Pressure Sensor "A" Circuit Range/Performance."
Can I drive with a P0191 code?
Drive only as needed until it is checked. Depending on the system, the engine may hesitate, stall or enter a reduced-power mode, and on direct-injection or diesel engines fuel pressure problems can cause sudden loss of power.
Is P0191 the sensor or the fuel pump?
It can be either. The code means the reading does not make sense, so measure actual fuel pressure: if it is correct, the sensor or wiring is suspect; if it is wrong, the fuel supply is the problem.
Is it safe to test fuel pressure on a direct-injection engine myself?
High-pressure fuel systems on direct-injection and diesel engines operate at very high pressures and need proper procedures and equipment. Most DIYers should rely on scan data and leave high-pressure testing to a professional.
Keep researching
Engine guides by brand (known issues, specs)
More fuel & air metering codes
Sources
- SAE J2012 — Diagnostic Trouble Code Definitions (standard code titles)
- ISO 15031-6 — Road vehicles: communication between vehicle and external equipment for emissions-related diagnostics, Part 6: Diagnostic trouble code definitions
- U.S. EPA — Vehicle Emissions Inspection and Maintenance (I/M) programs
- U.S. EPA, 40 CFR 86.1806-17 — Federal onboard diagnostics requirements for light-duty vehicles
- California Air Resources Board — On-Board Diagnostic (OBD) Program
General information written by CarWhere Research, not a diagnosis of your vehicle. Manufacturers can add their own sub-definitions and test conditions; confirm with the factory service information for your year, make and model. Before paying for a repair, check NHTSA for open recalls and your warranty booklet: federal law requires an emissions warranty on major emission-control parts such as the catalytic converter and engine computer.