P0191 — Fuel Rail Pressure Sensor Circuit Range/Performance

What P0191 means

The engine control unit constantly compares the fuel rail pressure sensor reading with the pressure it expects for the current operating conditions. P0191 is set when that signal is out of range, erratic or does not match what the engine is doing. The cause can be the sensor, its wiring, or a real fuel pressure problem.

Symptoms

• Check Engine light on
• Reduced power and sluggish acceleration
• Long cranking or hard starting
• Rough idle
• Hesitation or surging under throttle
• Worse fuel economy
• Limp mode or intermittent stalling

Possible causes

1. Failed fuel rail pressure sensor
2. Damaged or corroded sensor wiring or connector
3. Actual low or high fuel pressure
4. Faulty fuel pressure regulator or pressure control valve
5. Weak fuel pump or clogged fuel filter
6. Control module input circuit fault (uncommon)

How to diagnose

1. Scan all codes and freeze-frame data, noting companion codes such as P0087 and P0088
2. Inspect the sensor harness and connector for damage, corrosion, oil or fuel contamination
3. Check sensor reference voltage, ground and signal wire
4. Compare specified and actual rail pressure at cranking, idle and under load
5. Test low-pressure fuel supply for pressure and volume
6. Check the regulator or pressure control valve operation
7. Where applicable, measure injector return flow
8. Verify the sensor reading against a mechanical gauge

Common fixes

• Replace the fuel rail pressure sensor
• Repair the wiring or replace damaged connectors
• Replace the fuel filter or fuel pump if supply is weak
• Replace the pressure regulator or control valve
• Diagnose and, as a last resort, replace the control module

P0191 on different brands

Genesis

On Genesis the code appears as P0191:00 and indicates a fuel rail pressure sensor circuit range/performance fault; details from a specific bulletin should not be applied to other models.

Questions and answers

What does P0191 mean?

The engine computer sees a fuel rail pressure sensor signal that is out of range or doesn't match operating conditions. The cause may be the sensor, the wiring, or a real fuel pressure issue.

Can I drive with P0191?

Only a short distance to a repair shop. The engine can lose power, hesitate or stall, so don't put the repair off.

Do I always need a new sensor?

No. Check the wiring, connector and actual fuel pressure first. Replace the sensor if its supply is good but its reading disagrees with a mechanical gauge.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.