Code Definition

P0191 — Fuel Rail Pressure Sensor Circuit Range/Performance

System: Powertrain  |  Type: Generic (OBD-II Standard)  |  Make: Generic

About P0191

P0191 is a generic (obd-ii standard) powertrain diagnostic trouble code. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P0191 is stored, the module has detected a plausibility fault — the measured value is in the electrical range but is not consistent with expected operating behaviour; and a sensor-related fault — the reported value from the named sensor is out of spec.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

Because P0191 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

The P0191 fault code is set when the Engine Control Module (ECM) detects that the range or performance of the fuel rail pressure sensor circuit is outside of the expected parameters. This sensor is critical for monitoring the pressure of the fuel within the fuel rail, which is essential for correct fuel delivery and efficient combustion in the engine. The sensor's data allows the ECM to regulate fuel injector operation and overall fuel pressure. Deviations in the sensor's range or performance might indicate issues such as sensor malfunctions, improper calibration, or problems with the wiring o...

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