The OBD2 code P0091 is defined as “Fuel Pressure Regulator Control Circuit Low,” indicating an issue with the electrical circuit that controls the fuel pressure regulator. This problem can lead to symptoms such as reduced engine power, intermittent stalling, rough idle, and loss of power under acceleration,
P0091 quick overview
| Meaning | P0091: Fuel Pressure Regulator Control Circuit Low |
| Is it serious? | Yes, it can affect the vehicle’s performance and fuel efficiency. |
| Possible causes | – Faulty fuel pressure regulator – Damaged wiring or connectors – Problems with the fuel system – ECM software needing an update |
| How to diagnose? | Inspect wiring and connectors for damage or corrosion. Check the fuel pressure regulator for proper operation. Verify fuel pressure against manufacturer specifications. Consider ECM software updates to correct potential issues. |
P0091 Meaning
Encountering a P0091 code means there’s a problem in the system that helps control how much fuel gets into your engine. If the circuit that tells the fuel pressure regulator what to do isn’t working right, your car might not run as it should. This could be because of a bad regulator, wires that are damaged, or other fuel system troubles.
Fixing it usually involves looking closely at these parts, making sure they’re all in good shape and doing what they’re supposed to do. Sometimes, updating the car’s computer software is all it takes to get everything working right again.
Car Diagnostics Training
- Car Electrical basics
- OBD-II scanner basics
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- Introduction to a Bi-directional Scan tool
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How to fix P0091 – learn from mechanics
I looked into P0091 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.
Case #1: Dodge P0091
Vehicle information
2004 Dodge Sprinter 3500 2.7L
Issue + repair history
- Initial complaint of engine having no power upon purchase, but running normal the next morning
- DTC P0091 for a fuel pressure control circuit low fault detected
- No relevant information found in Mitchell or Alldata databases
- Regular maintenance up to date
Other OBD2 Codes + Test Results
- Code P0091: fuel pressure regulator control circuit low
Mechanic suggestions
- Verify the accuracy of the scan tool being used, as aftermarket scanners may provide inaccurate codes
- Common recurring problems on 2004 Sprinters include EGR valve failure, collapsed MAF sensor inlet, and issues with the turbo boost solenoid system
- Check for EGR valve malfunction, collapsed MAF sensor inlet, and turbo boost solenoid system issues
- Investigate potential ECM problems or leaking fuel injectors, as they could cause hard starting issues related to the P0091 code
Final fix
- Replaced fuel pressure regulator
Case #2: Ford P0091
Vehicle information
2015 Ford F-250 Super Duty 6.7L
Issue + repair history
- Customer complained of reduced engine power and intermittent stalling
- DTC P0091 for fuel pressure regulator control circuit low detected
- Previous repairs included replacement of the fuel filter and fuel pressure sensor, but issue persisted
Other OBD2 Codes + Test Results
- Code P0091: fuel pressure regulator control circuit low
Mechanic suggestions
- Check the wiring harness and connectors associated with the fuel pressure regulator for any signs of damage or corrosion
- Perform a thorough inspection of the fuel pressure regulator itself, as it may be malfunctioning and causing the low circuit fault
- Verify proper fuel pressure readings and compare them to manufacturer specifications
- Consider performing a software update or reflash on the engine control module to address any potential software-related issues contributing to the fault code
Final fix
- Replaced faulty fuel pressure regulator and cleared DTCs, issue resolved.
Case #3: Chevrolet P0091
Vehicle information
2012 Chevrolet Silverado 2500HD 6.6L Duramax
Issue + repair history
- Owner reported rough idle and loss of power under acceleration
- Diagnostic scan revealed DTC P0091 for fuel pressure regulator control circuit low
- Previous repairs included replacement of the fuel filter and fuel pressure sensor, but symptoms persisted
Other OBD2 Codes + Test Results
- Code P0091: fuel pressure regulator control circuit low
Mechanic suggestions
- Inspect the wiring harness and connectors related to the fuel pressure regulator for any signs of damage or loose connections
- Test the fuel pressure regulator for proper functionality and ensure it is receiving the correct voltage signals
- Check for any restrictions or leaks in the fuel system that could be causing inadequate fuel pressure
- Perform a comprehensive fuel system inspection, including fuel line integrity and fuel injector performance
Final fix
- Discovered a damaged wiring harness connector leading to the fuel pressure regulator. Repaired the wiring and cleared DTCs, resolving the issue.
How to diagnose P0091
I made you an overview of solving this DTC, based on all the advice that was suggested by certified mechanics to address this issue in previously mentioned service cases.
| Diagnostic Step | Brief Explanation |
|---|---|
| Inspect wiring and connectors | Looks for any electrical problems that could cause the code. |
| Check the fuel pressure regulator | Tests if the regulator itself is faulty or malfunctioning. |
| Verify fuel pressure | Ensures the fuel system is providing the right amount of pressure. |
| Update ECM software | Corrects any software glitches that might be causing the issue. |
Car Diagnostics Training
- Car Electrical basics
- OBD-II scanner basics
- How to use an OBD reader
- Introduction to a Bi-directional Scan tool
- OBD scanner buyer’s guide + discounts
I test OBD-II scanners and make DIY Engine diagnostics guides to help you solve your car problems without having to depend on the mechanic. A lot of them will try to scam you or are just no help at all. About Juraj Lukacko