Fuel Rail Pressure Sensor A Circuit Range/Performance
The DURAMAX-P0191 (Duramax) diesel fault code means: Fuel Rail Pressure Sensor A Circuit Range/Performance. This is a serious severity code.
- Keep driving?
- No — stop driving
- DIY difficulty
- advanced
- Estimated cost
- $400-$800 FPR, $7,000-$12,000 full CP4 failure repair, $4,500-$6,000 CP3 conversion
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View pilot availability →What Are the Symptoms of DURAMAX-P0191?
- Extended cranking or no start
- Loss of power / 'Reduced Engine Power' message
- Limp mode
- Metal shavings in fuel filter (if CP4 failed)
- Strong fuel smell
What Causes DURAMAX-P0191? (Most Likely First)
- FRP sensor drift Very Likely
- Failed fuel pressure regulator / FCA valve Likely
- Plugged fuel filter (service interval every 15K) Possible
- Air in fuel system Less Likely
- Cracked high-pressure fuel line Less Likely
Can I Still Drive with DURAMAX-P0191?
No — stop driving. DURAMAX-P0191 is rated serious severity. Continuing to drive in this state risks further damage — get it looked at before your next trip.
Frequently Asked Questions
What is P0191 on a Duramax?
Duramax code P0191 (Fuel Rail Pressure Sensor A Circuit Range/Performance) is a serious-severity diagnostic trouble code triggered by the engine control module when it detects a problem in the associated system. The Bosch CP4.2 pump in LML and L5P Duramax engines is known for catastrophic self-destruction, contaminating the entire fuel system.
Is a Duramax P0191 safe to drive?
NO. If the CP4 pump has failed, continuing to drive spreads metal through injectors, lines, and tank. Tow to the shop.
How much does it cost to fix P0191 on a Duramax?
FPR $400-$800. Plugged filter $40-$100. Full CP4 failure $7,000-$12,000. CP3 conversion $4,500-$6,000.
Mechanics Guide Step-by-step diagnosis
How Do You Diagnose DURAMAX-P0191?
Pull the fuel filter and inspect for metal debris. Metal = entire fuel system contaminated, requires full replacement.
Check fuel rail pressure with scan tool at key-on and during crank. Should see ~5,000+ psi at crank on LML/L5P
Test the fuel pressure regulator before condemning the pump — cheaper to replace first
Inspect fuel tank pickup and lift pump output
If CP4 pump has failed, recommend a CP3 conversion kit to prevent repeat failure
Sources 1
This page is built from documented references. Verify against your own service info before repair work.
- SAE J2012Diagnostic Trouble Code Definitions (defines P0191 as a generic OBD-II code)
P0191 on Other Platforms
The same code ID appears across other engines, vehicles, and equipment. Diagnostic flow varies by platform — see the matching breakdown:
Which Vehicles Commonly Get DURAMAX-P0191?
- 2001-2004 Chevy Silverado 2500/3500 HD 6.6L Duramax LB7
- 2001-2004 GMC Sierra 2500/3500 HD 6.6L Duramax LB7
- 2004.5-2005 Chevy Silverado 2500/3500 HD 6.6L Duramax LLY
- 2004.5-2005 GMC Sierra 2500/3500 HD 6.6L Duramax LLY
- 2006-2007 Chevy Silverado 2500/3500 HD 6.6L Duramax LBZ
- 2006-2007 GMC Sierra 2500/3500 HD 6.6L Duramax LBZ
- 2007.5-2010 Chevy Silverado 2500/3500 HD 6.6L Duramax LMM
- 2007.5-2010 GMC Sierra 2500/3500 HD 6.6L Duramax LMM
- 2011-2016 Chevy Silverado 2500/3500 HD 6.6L Duramax LML
- 2011-2016 GMC Sierra 2500/3500 HD 6.6L Duramax LML
- 2017+ Chevy Silverado 2500/3500 HD 6.6L Duramax L5P
- 2017+ GMC Sierra 2500/3500 HD 6.6L Duramax L5P
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