KlaroFault codeP0191
MODERATEFuel Rail Pressure Sensor Circuit Range/Performance
What this code means
Fuel Rail Pressure Sensor Circuit Range/Performance.
P0191 is a generic code: it means the same thing on every make. P0191 belongs to family P01xx — Fuel and air metering. Its page explains how to read a code and groups all its codes by part.
Type of fault
The signal stays within its electrical limits, but its value is not plausible: it does not match what the control unit expects given the other sensors. The sensor may be drifting with age, but it may also be faithfully measuring a real mechanical problem — a leak, a blockage, an air leak. Replacing the sensor without checking does not always clear the fault.
Fuel rail pressure sensor
On direct-injection and common-rail diesel engines, this sensor at the end of the fuel rail measures the high pressure delivered to the injectors, from tens to more than two thousand bar. The control unit uses it to regulate the pump and to calculate the injection time.
What you notice
Hard or impossible starting, sudden loss of power, limp mode, sometimes stalling.
How to check it
The sensor is often screwed into the rail and replaced together with it on some engines. Check the connector and wiring first. In Klaro, rail pressure at idle should be stable and rise sharply when you accelerate; a reading frozen or impossible with the engine off points to the sensor or its circuit.
Watch it live in Klaro
With an OBD2 adapter plugged in, these live readings show the part at work, when your car reports them:
- Fuel rail pressure (absolute)
- Fuel rail absolute pressure
- Fuel rail pressure (relative)
What to do
Have it checked this week. The car remains usable, but the fault will not clear itself and will fail the roadworthiness test.
Clearing a code switches the light off but repairs nothing: if the fault remains, the code comes back. Clearing a fault code yourself →
How to read this code
- PPowertrain
- 0standardised code
- 1Fuel and air metering
- 91P0191
