P0191 on RAM: How to Diagnose & Fix
Fuel Rail Pressure Sensor Circuit Range/Performance
1 RAM model · 1 documented issue · 1 critical · $8,000-$12,000 repair
P0191 on RAM by model: symptoms, diagnosis and fix
The 2019+ RAM 2500 with the 6.7L Cummins diesel uses a Bosch CP4.2 high-pressure fuel injection pump that is prone to catastrophic self-destruction. The CP4.2 relies on diesel fuel for internal lubrication, and any contamination, water intrusion, or low fuel levels cause the pump to disintegrate, sending metal shavings throughout the entire fuel system. This contaminates fuel injectors ($500+ each x6), fuel rails, fuel lines, and the fuel tank, requiring a complete fuel system replacement costing $8,000-12,000+. The previous-generation CP3 pump was far more reliable. Multiple class-action lawsuits have been filed against Stellantis/Bosch.
Common Symptoms
- Engine no-start or sudden loss of power
- Metallic debris in fuel filter
- Loud knocking or grinding from fuel pump area
- Check engine light with fuel pressure codes (P0087, P0088, P228D)
- Excessive cranking before starting
- Fuel filter clogging frequently
- White or black smoke from exhaust
How to Fix
If the CP4.2 has failed, the ENTIRE fuel system must be replaced or thoroughly cleaned: fuel pump, all 6 injectors (Bosch 0445120413), fuel rails, high-pressure fuel lines, fuel tank (or professionally cleaned), and fuel filter. Total cost: $8,000-12,000+ at dealer. Prevention: Install a FASS or AirDog lift pump system ($800-1,200) that provides additional fuel filtration and water separation before the CP4.2. Some owners proactively replace the CP4.2 with a CP3 conversion kit ($3,000-4,500) from S&S Diesel Motorsport or Fleece Performance for permanent reliability.
Sources for this issue (1)
P0191 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0191 mean on a RAM?
P0191 stands for "Fuel Rail Pressure Sensor Circuit Range/Performance." This code sets when the fuel rail pressure sensor's signal is out of its expected range or doesn't match what the computer expects for current conditions. On direct-injection and many modern engines, this sensor reports fuel pressure in the rail so the computer can precisely control fueling and the fuel pump. When the reading is implausible — too steady, erratic, or inconsistent with commanded pressure — this code is set, sometimes with hard starting, hesitation, or reduced power. It generally points to the sensor or its wiring, though an actual fuel-pressure problem can also trigger it. On RAM it is documented across 1 model: 2500.
What are the most common causes of P0191?
The most common causes of P0191 are: Faulty fuel rail pressure sensor, Corroded, loose, or damaged sensor connector, Open, shorted, or high-resistance sensor wiring, Actual fuel pressure out of range (weak pump or regulator), Restricted fuel filter or supply line, Loss of reference voltage or ground from the ECM/PCM, Faulty fuel pressure regulator or control valve. The specific cause varies by vehicle.
How much does it cost to fix P0191 on a RAM?
Published repair estimates on RAM range from $8,000 to $12,000 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P0191 on a different make?
View P0191 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.