Code Definition

P0091 — Fuel Pressure Regulator 1 Control Circuit Low

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

About P0091

P0091 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 P0091 is stored, the module has detected a signal or supply voltage lower than the expected operating range.

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 P0091 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 P0091 code indicates a low voltage condition in the control circuit of Fuel Pressure Regulator 1. This regulator plays a critical role in managing the fuel pressure supplied to the engine's fuel injectors. The Engine Control Module (ECM) sets this code when it detects that the voltage in the control circuit for the fuel pressure regulator is lower than expected. Such a low voltage condition can lead to issues in fuel delivery, potentially affecting engine performance, efficiency, and emissions.

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