P0091
Fix within a few daysFuel Pressure Regulator 1 Control Circuit Low
Code P0091 means the engine computer detects a low voltage in the fuel pressure regulator's control circuit. Common causes: Faulty fuel pressure regulator (60%), wiring issues (30%). Drivability: No, stop driving. Repair cost: $100-$350 DIY, $250-$800 professional.
Can I Drive With P0091?
No, stop driving
Immediate repair needed. Driving with this code can cause unexpected stalling, leaving you stranded, and potentially damaging other engine components.
Stop driving immediately if: Engine stalls, won't start, significant power loss, or any unusual noises.
Symptoms of P0091
- 1Check Engine Light on
- 2Engine cranks but won't start
- 3Hard starting
- 4Engine stalling
- 5Rough idle
- 6Reduced engine power
- 7Poor acceleration
Common Causes of P0091
Parts most likely causing this code, ranked by probability
The internal solenoid or control circuit within the fuel pressure regulator is faulty, causing a low voltage signal back to the engine computer.
60% of P0091 cases are fixed by replacing this part
A damaged wire, loose connection, or corrosion in the fuel pressure regulator's control circuit can cause a low voltage reading.
30% of P0091 cases are fixed by repairing wiring or connectors
A rare internal fault in the engine control module's driver circuit for the fuel pressure regulator can cause this code.
10% of P0091 cases are fixed by replacing the ECM/PCM
Check These First (Before Buying Parts)
- Visually inspect the electrical connector at the fuel pressure regulator for any signs of corrosion, damage, or loose pins.
- Check the wiring harness leading to the fuel pressure regulator for any chafing, cuts, or signs of rodent damage.
How to Diagnose P0091
- 1Visually inspect the fuel pressure regulator and its electrical connector for damage, corrosion, or loose wires.
- 2Using a multimeter, check for proper voltage and ground at the FPR connector with the key on.
- 3Check the resistance of the fuel pressure regulator's solenoid (if applicable and accessible) to ensure it's within specifications.
- 4If wiring and FPR test good, consider testing fuel pressure with a mechanical gauge to confirm actual fuel rail pressure.
- 5If all else checks out, a professional diagnosis of the ECM/PCM may be necessary.
P0091 on Popular Vehicles
Ford F-150
2011-2020P0091 on EcoBoost engines can sometimes be related to the low-pressure fuel pump control module or wiring issues leading to the high-pressure fuel pump's regulator.
65% fixed by FPR, 25% by wiring
Chevrolet Silverado
2007-2024P0091 is common on Duramax engines and often points to a faulty fuel pressure regulator (also called fuel rail pressure sensor/regulator) on the high-pressure fuel pump or the fuel rail. Wiring harness issues are also frequent.
70% fixed by FPR, 20% by wiring
Ram 2500/3500
2007-2024Similar to Duramax, P0091 on Cummins engines frequently indicates a problem with the fuel pressure regulator (FPR) on the CP3 or CP4 high-pressure fuel pump, or its electrical connector/harness.
70% fixed by FPR, 20% by wiring
Frequently Asked Questions
What does P0091 mean?
P0091 indicates the engine computer has detected a low voltage condition in the control circuit for the fuel pressure regulator. This means the computer isn't getting the expected electrical signal from or to the regulator.
Can I drive with P0091?
No, stop driving. A faulty fuel pressure regulator can cause severe engine performance issues, including stalling, hard starting, and potential engine damage.
Will P0091 clear itself?
No, P0091 will not clear itself. The underlying electrical or mechanical fault must be repaired before the code will clear.
How do I fix P0091 myself?
Start by inspecting the fuel pressure regulator's wiring and connector for damage. If the wiring is good, test the regulator's electrical resistance with a multimeter. If it's out of spec, replace the fuel pressure regulator.
How much does it cost to fix P0091?
DIY costs range from $100-$350 for a new fuel pressure regulator and basic tools. Professional repair costs typically range from $250-$800, including parts and labor.
P0091 keeps coming back - why?
If P0091 returns, it means the initial repair did not address the root cause. This could be due to a persistent wiring issue, a faulty new part, or a rare ECM problem.
Will P0091 fail emissions/smog test?
Yes, P0091 will cause your vehicle to fail an emissions or smog test. The Check Engine Light being on is an automatic failure, and fuel system issues directly impact emissions.
What's the difference between P0091 and P0092?
P0091 indicates a 'low' voltage condition in the fuel pressure regulator control circuit, meaning the voltage is too low. P0092 indicates a 'high' voltage condition, meaning the voltage is too high. Both point to an electrical issue with the regulator's control.
P0091 on Ford F-250/350 6.7L Powerstroke?
P0091 on a Ford 6.7L Powerstroke often points to an issue with the fuel pressure control valve (FPCV) or the fuel volume control valve (FVCV) on the high-pressure fuel pump, or their wiring. These are common failure points on these diesel engines.
Questions to Ask Your Mechanic
Did you check the voltage and ground at the fuel pressure regulator connector?
Good answer: Yes, I confirmed the correct voltage and ground signals are present, which tells me the wiring from the ECM is good. The issue is likely internal to the regulator itself.
What was the resistance reading of the fuel pressure regulator solenoid?
Good answer: I measured the resistance at X ohms, which is outside the factory specification of Y-Z ohms, indicating an internal fault with the regulator.
Repair Cost Estimate
DIY Repair
Parts only
$100-$350
Shop Repair
Parts + labor
$250-$800
Save $150-$450 by doing it yourself
Difficulty
intermediate
Time
1-3 hours
Intermediate. Requires a multimeter and understanding of electrical diagnostics, along with basic mechanical skills.
Cost of Waiting
Ignoring P0091 can lead to your vehicle stalling unexpectedly, becoming undrivable, or causing long-term damage to your fuel system components or even the engine due to incorrect fuel delivery. A $100-$350 fuel pressure regulator replacement now prevents being stranded or facing more expensive repairs later.
While You're In There...
While not directly causing P0091, a restricted fuel filter can sometimes put strain on the fuel system. If you're working on fuel system components, it's a good preventative maintenance item.
If you're disconnecting fuel lines to access the regulator, replacing the O-rings or seals prevents leaks and ensures a tight seal upon reassembly.
Tools You'll Need
- OBD-II scan tool
- Multimeter
- Basic hand tools (sockets, wrenches, screwdrivers)
- Safety glasses
- Shop rags
P0091 is a common fuel system code that points to an electrical issue with the fuel pressure regulator. While it can cause serious drivability problems, it's a fixable issue, and getting it repaired promptly will restore your vehicle's performance and reliability.
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Your Next Steps
Step 1: Visually inspect the fuel pressure regulator's electrical connector and wiring harness for any obvious damage, corrosion, or loose connections. Ensure the connector is fully seated.
Step 2: If the visual inspection doesn't reveal any issues, use a multimeter to test for proper voltage and ground at the fuel pressure regulator connector. Compare your readings to your vehicle's service manual specifications.
Step 3: If the wiring and voltage are correct, disconnect the fuel pressure regulator and test its internal resistance with a multimeter. If the resistance is outside the manufacturer's specified range, replace the fuel pressure regulator.