P20EE on RAM: How to Diagnose & Fix
SCR NOx Catalyst Efficiency Below Threshold
1 RAM model · 1 documented issue · 1 critical · $300-$3,500 repair
P20EE 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)
P20EE 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 P20EE mean on a RAM?
P20EE stands for "SCR NOx Catalyst Efficiency Below Threshold." This is a diesel emissions code meaning the Selective Catalytic Reduction (SCR) catalyst on Bank 1 is not cleaning up exhaust as well as it should. The SCR system sprays Diesel Exhaust Fluid (DEF) into the hot exhaust to convert harmful nitrogen oxides (NOx) into harmless nitrogen and water; NOx sensors before and after the catalyst tell the computer how well it is working. When the measured efficiency falls below the required threshold, this code sets. Because it is an emissions-protection code, it often triggers warning lights and can lead to reduced power or a speed limit (a 'derate') if left unfixed. On RAM it is documented across 1 model: 2500.
What are the most common causes of P20EE?
The most common causes of P20EE are: Poor quality, contaminated, or wrong DEF fluid, Faulty or clogged DEF injector/dosing valve, Failed upstream or downstream NOx sensor, Degraded or failed SCR catalyst, Exhaust gas temperature sensor fault affecting dosing, Exhaust or DEF line leak, DEF line/heater problems (crystallization or freezing). The specific cause varies by vehicle.
How much does it cost to fix P20EE 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 P20EE on a different make?
View P20EE 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.