What are the common causes of P0091?

A short to ground on the regulator A control wire. A regulator A solenoid with low internal resistance. A weak voltage supply to the regulator A circuit. Corroded pins at the regulator A connector. A faulty PCM driver holding the circuit low.

Inspect the regulator A wiring for a pinch or chafe to ground. Check supply voltage at the regulator A connector under load. Measure the regulator A solenoid resistance against spec. Disconnect the PCM and check the control wire for a ground short. Replace the fuel pressure regulator A if the solenoid is shorted. Clear the code and retest.

P0091

Fuel Pressure Regulator A Control Circuit Low

System: Fuel and air metering (P code)
Lamp: Check Engine Light
Category: Powertrain - Fuel/Air Metering

What it means

P0091 means Fuel Pressure Regulator A Control Circuit Low.

Check these first

A short to ground on the regulator A control wire
A regulator A solenoid with low internal resistance
A weak voltage supply to the regulator A circuit
Corroded pins at the regulator A connector
A faulty PCM driver holding the circuit low

What to do next

Inspect the regulator A wiring for a pinch or chafe to ground
Check supply voltage at the regulator A connector under load
Measure the regulator A solenoid resistance against spec
Disconnect the PCM and check the control wire for a ground short
Replace the fuel pressure regulator A if the solenoid is shorted
Clear the code and retest

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Updated

Generic SAE J2012 definition. Last updated 2026-10-10.