P249F on RAM: How to Diagnose & Fix
Diesel Particulate Filter Pressure Sensor Intermittent/Erratic (Bank 2)
1 RAM model · 1 documented issue · 1 critical · $300-$3,500 repair
P249F on RAM by model: symptoms, diagnosis and fix
The 2013+ RAM 2500 6.7L Cummins diesel DEF (Diesel Exhaust Fluid) system is plagued with failures of the DEF heater, DEF pump, DEF injector, NOx sensors, and SCR catalyst. The DEF system is required for emissions compliance, and when it fails, the truck enters a "limp mode" that limits speed to 5 mph after a countdown timer expires. DEF heater failures are most common in cold climates where the fluid freezes and cracks the heater element. TSB 18-018-20 addresses DEF heater and quality sensor issues. The NOx sensors (inlet and outlet) fail frequently at $300-500 each.
Common Symptoms
- DEF system warning light or message
- Speed limited to 5 mph (limp mode)
- Check engine light with SCR-related codes (P20EE, P2BAD, P2201)
- DEF quality poor message despite fresh fluid
- DEF tank not reading correct level
- Truck will not restart after shutdown (DEF lockout)
- Ammonia smell from exhaust
How to Fix
Diagnose with Cummins INSITE or wiTECH to identify the specific DEF component failure. Common repairs: DEF heater replacement ($400-800, Mopar 68322877AA), DEF pump/injector assembly ($600-1,000), NOx sensor replacement ($300-500 each, two sensors). If SCR catalyst is failed, replacement costs $2,000-3,500. Check TSB 18-018-20 for updated DEF heater and quality sensor procedures. Use only API-certified DEF fluid (ISO 22241 standard). Avoid storing DEF over 1 year as it degrades.
Sources for this issue (5)
P249F 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 P249F mean on a RAM?
P249F stands for "Diesel Particulate Filter Pressure Sensor Intermittent/Erratic (Bank 2)." This is a diesel emissions code. The diesel particulate filter (DPF) traps soot from the exhaust, and a pressure sensor measures the pressure difference across the filter so the computer knows how full it is and when to run a cleaning (regeneration) cycle. P249F means the DPF pressure sensor signal on Bank 2 is intermittent or erratic — the reading jumps around or cuts out unpredictably rather than staying steady. This can cause the computer to misjudge soot levels, trigger unnecessary or failed regenerations, and may put the engine into a reduced-power mode. On RAM it is documented across 1 model: 2500.
What are the most common causes of P249F?
The most common causes of P249F are: Faulty or aging DPF differential pressure sensor, Loose, cracked or kinked pressure sensor hoses/tubes, Soot, moisture or carbon clogging the sensor lines, Loose or intermittent electrical connector at the sensor, Chafed or partially broken sensor wiring, Corrosion or water intrusion in the connector, Faulty ECM/sensor reference signal (less common). The specific cause varies by vehicle.
How much does it cost to fix P249F on a RAM?
Published repair estimates on RAM range from $300 to $3,500 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 P249F on a different make?
View P249F 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.