Damaged or chafed control wire shorting to ground; Corroded or loose electrical connector at the fuel pressure regulator; Failed fuel pressure regulator solenoid or control valve; Open circuit in the regulator control wiring or a blown fuse; Faulty engine control module driver for the regulator circuit; Internal short in the regulator causing excessive current draw

DTC codes / P00xx · Fuel and air metering and auxiliary emission controls / P0091

P0091Fuel Pressure Regulator 1 Control Circuit Low

Q: What does code P0091 mean?

Fuel Pressure Regulator 1 Control Circuit Low. P0091 means the engine computer has detected that the electrical circuit controlling the fuel pressure regulator on bank 1 is showing a low voltage condition, which usually indicates a short to ground or an open circuit. The regulator itself may be mechanical, but the computer is specifically reporting a problem with the control wire that commands it.

P0091 means the engine computer has detected that the electrical circuit controlling the fuel pressure regulator on bank 1 is showing a low voltage condition, which usually indicates a short to ground or an open circuit. The regulator itself may be mechanical, but the computer is specifically reporting a problem with the control wire that commands it.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering and auxiliary emission controls

Symptoms you may notice

Illuminated check engine light, often with no other noticeable symptoms
Rough idle or stumbling acceleration if the regulator is stuck at low pressure
Extended cranking before the engine starts, or a no-start condition
Reduced engine power or limp mode in some vehicles
Poor fuel economy or black smoke from the tailpipe if the regulator fails rich
Intermittent misfire codes or hesitation under load

Common causes, most likely first

Damaged or chafed control wire shorting to ground
Corroded or loose electrical connector at the fuel pressure regulator
Failed fuel pressure regulator solenoid or control valve
Open circuit in the regulator control wiring or a blown fuse
Faulty engine control module driver for the regulator circuit
Internal short in the regulator causing excessive current draw

How to diagnose and fix it

Scan all modules for stored codes and record freeze-frame data to confirm the fault conditions
Visually inspect the regulator connector and wiring for corrosion, chafing, or loose pins
Measure resistance of the regulator solenoid and compare to manufacturer specification
Check for voltage on the control wire with the key on and engine off, looking for a short to ground
Perform a wiggle test on the harness while monitoring live data to catch intermittent faults
If wiring and connector are good, test the regulator with a known-good unit or follow the factory diagnostic flow chart
Clear codes and verify the repair with a road test under the same conditions that set the original code

What the low circuit code really means

A low circuit code does not automatically condemn the regulator; a shorted wire or corroded connector is just as common and far cheaper to fix.
Some vehicles use a fuel pressure control module that can set P0091 even when the regulator itself is fine, so always check for related module codes.
The regulator may be mechanically stuck while the electrical circuit tests good, so live fuel pressure data is essential before replacing parts.
Intermittent P0091 codes often appear after engine wash or in wet weather when moisture enters a connector, so inspect for water intrusion.
A failed regulator can cause fuel to leak into the vacuum line on some designs, leading to rich running and a low circuit code simultaneously.

Can I keep driving with P0091?

You can usually drive cautiously to a repair shop if the engine runs smoothly and the light is steady, but avoid heavy acceleration or towing. If the engine stumbles, stalls, or the light flashes, stop driving and have the vehicle towed to prevent catalytic converter damage.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.