Faulty fuel rail pressure sensor (both sources). Damaged wiring, a poor connection, or excessive resistance in the sensor circuit (both sources). Actual fuel pressure that is too high or too low (OBD-Codes.com). Low fuel or running out of fuel (OBD-Codes.com). Vacuum leaks, including the sensor's vacuum hose on engines that use one (OBD-Codes.com). Faulty fuel pressure regulator (RepairPal). Less often: a PCM fault, which OBD-Codes.com suggests only after every other test has passed.

Repair damaged wiring or a corroded or loose connector at the sensor (or at the PCM). Fix a leaking vacuum hose to the sensor, if your engine uses one. Replace the fuel rail pressure sensor (on some engines it is part of the fuel rail, per OBD-Codes.com). If a gauge shows the real pressure is wrong or erratic, repair the fuel delivery problem, such as the pump or the pressure regulator (both sources).

P0191⛽ Fuel / fuel rail pressure sensorStop and fix promptly

P0191: Fuel Rail Pressure Sensor Range/Performance (Meaning, Causes, Fixes)

Q: What does P0191 mean?

P0191 means the engine computer thinks the fuel rail pressure sensor's reading doesn't make sense: it is erratic or doesn't match the fuel actually being delivered. It can be a bad sensor or wiring, but it can also be real fuel pressure trouble (too high, too low, or running low on fuel). Comparing the scan-tool reading with a mechanical fuel pressure gauge tells you which. The fuel rail pressure (FRP) sensor tells the engine computer (PCM) how much pressure is in the fuel rail feeding the injectors, so it can meter the right amount of fuel. P0191 is a range/performance code: the signal is present but doesn't behave the way the PCM expects. OBD-Codes.com says it is a generic code for most fuel-injected gas and diesel engines since about 2000, and that it is strictly about the sensor signal not matching what is being delivered to the engine, which can be a mechanical or an electrical fault. RepairPal describes the trigger as an erratic sensor signal indicating an abnormal fuel pressure condition. The sources differ on causes: OBD-Codes.com includes actual high or low fuel pressure, vacuum leaks, circuit resistance and low or no fuel, while RepairPal lists the sensor, its circuit or connector, and the fuel pressure regulator. Unlike P0193 (signal reads high), P0191 doesn't say which direction the reading is off.

Q: Can I keep driving with P0191?

Stop and fix promptly. RepairPal puts P0191 in its urgent category, meaning action is needed right away because it can cause severe damage or put the people in the car at risk. RepairPal lists hesitation and stalling (including dying at stop signs) as symptoms, and OBD-Codes.com says the engine may lack power or crank but not start. A stall in traffic is dangerous, so get it diagnosed promptly, and have it towed if the engine stalls or hesitates badly. Fuel in the rail is under pressure, and diesel common-rail systems run extremely high pressure, so do not open or loosen anything on the fuel rail yourself.

Reviewed 2026-10-23 · Based on 2 cited source(s)

What P0191 means

The fuel rail pressure (FRP) sensor tells the engine computer (PCM) how much pressure is in the fuel rail feeding the injectors, so it can meter the right amount of fuel. P0191 is a range/performance code: the signal is present but doesn't behave the way the PCM expects. OBD-Codes.com says it is a generic code for most fuel-injected gas and diesel engines since about 2000, and that it is strictly about the sensor signal not matching what is being delivered to the engine, which can be a mechanical or an electrical fault. RepairPal describes the trigger as an erratic sensor signal indicating an abnormal fuel pressure condition. The sources differ on causes: OBD-Codes.com includes actual high or low fuel pressure, vacuum leaks, circuit resistance and low or no fuel, while RepairPal lists the sensor, its circuit or connector, and the fuel pressure regulator. Unlike P0193 (signal reads high), P0191 doesn't say which direction the reading is off.

Severity: can I keep driving?

Stop and fix promptly

RepairPal puts P0191 in its urgent category, meaning action is needed right away because it can cause severe damage or put the people in the car at risk. RepairPal lists hesitation and stalling (including dying at stop signs) as symptoms, and OBD-Codes.com says the engine may lack power or crank but not start. A stall in traffic is dangerous, so get it diagnosed promptly, and have it towed if the engine stalls or hesitates badly. Fuel in the rail is under pressure, and diesel common-rail systems run extremely high pressure, so do not open or loosen anything on the fuel rail yourself.

Common symptoms

Check engine light on (both sources)
Lack of power (OBD-Codes.com)
Engine cranks but won't start (OBD-Codes.com)
Engine hesitation or stalling, including dying at stop signs (RepairPal)
Higher fuel consumption and an unusual exhaust smell (RepairPal)
A rich (P0172) or lean (P0171) fuel trim code may also set (RepairPal)
Failed emissions test, or in rare cases no noticeable symptoms (RepairPal)

Likely causes

Roughly most to least common, based on the sources below. Your vehicle may differ.

Faulty fuel rail pressure sensor (both sources)
Damaged wiring, a poor connection, or excessive resistance in the sensor circuit (both sources)
Actual fuel pressure that is too high or too low (OBD-Codes.com)
Low fuel or running out of fuel (OBD-Codes.com)
Vacuum leaks, including the sensor's vacuum hose on engines that use one (OBD-Codes.com)
Faulty fuel pressure regulator (RepairPal)
Less often: a PCM fault, which OBD-Codes.com suggests only after every other test has passed

Diagnostic steps you can do

⚠ Before you start

Work on a cool engine, parked on level ground with the parking brake set. Never work under a car supported only by a jack.

Make sure there's enough fuel in the tank, since OBD-Codes.com lists low or no fuel as a cause.
Look up technical service bulletins (TSBs) for your year, make, model and engine (OBD-Codes.com).
Check for other fuel pump or fuel pressure codes. OBD-Codes.com says to diagnose those first, especially with a no-start.
Find the fuel rail pressure sensor and inspect its connector and wiring for chafing, bare wires, burn marks, melted plastic or corroded (green) terminals. Clean corroded terminals with electrical contact cleaner and add dielectric grease (OBD-Codes.com).
If the sensor has a vacuum hose to the intake manifold, check it and its connections for leaks (OBD-Codes.com).
Clear the code with a scan tool and see if it returns. If it doesn't, the connection was likely the problem (OBD-Codes.com).
If it comes back, compare the scan tool's fuel pressure reading with a mechanical fuel pressure gauge. OBD-Codes.com says they should be within 5 psi of each other with the key on. Fuel is under pressure and flammable, so leave the gauge test to a shop if you aren't set up for it.

Typical fixes

Repair damaged wiring or a corroded or loose connector at the sensor (or at the PCM)
Fix a leaking vacuum hose to the sensor, if your engine uses one
Replace the fuel rail pressure sensor (on some engines it is part of the fuel rail, per OBD-Codes.com)
If a gauge shows the real pressure is wrong or erratic, repair the fuel delivery problem, such as the pump or the pressure regulator (both sources)

Repair costs vary widely by vehicle, region, parts brand and shop, so we don't quote prices. Get a written estimate after diagnosis.

🛠 When to call a pro

RepairPal's shop procedure: read freeze frame data, watch the fuel pressure reading on a test drive, confirm with a mechanical gauge, check the sensor circuit with a lab scope, and if real pressure is erratic, inspect the fuel delivery system and check the fuel pump's current draw
The sources rank the last resort differently: OBD-Codes.com says that if everything else passes, a failed PCM is most likely (after a battery-disconnect reset), while RepairPal says that with good wiring and normal real pressure, the sensor is most likely at fault
On diesel common-rail engines, OBD-Codes.com warns rail pressure is at least about 2,000 psi at warm idle and can exceed 35,000 psi under load; a leak can cut skin and cause blood poisoning, so have a professional replace the sensor
RepairPal lists common misdiagnoses: replacing the sensor when the real cause is the pressure regulator, the fuel pump, or a poor connection or chafed wiring

Where to buy

Plain search links. Always match parts to your exact year, make, model and engine.

OBD2 scanners on Amazon Parts at Advance Auto Parts catalog at RockAuto

FAQs

Is P0191 always a bad fuel pressure sensor?

No. OBD-Codes.com says it can be mechanical or electrical, including real high or low fuel pressure, vacuum leaks or low fuel, and RepairPal warns sensors are often replaced when the regulator, fuel pump or wiring is the real problem. A mechanical gauge check is the way to tell.

Can I drive with P0191?

RepairPal rates it urgent, and the sources list stalling, hesitation, lack of power or a no-start. Limit driving and get it checked soon; tow it if the engine stalls.

What's the difference between P0191 and P0193?

P0193 means the sensor signal reads too high. P0191 means the signal is erratic or doesn't match the fuel being delivered, without saying which way it's off.

Sources

Last reviewed 2026-10-23. Code definitions and repair steps can vary by manufacturer. Confirm with your vehicle's service information.