P20EE on Ford: How to Diagnose & Fix
SCR NOx Catalyst Efficiency Below Threshold
2 Ford models · 2 documented issues · 1 critical · $350-$4,500 repair
P20EE on Ford by model: symptoms, diagnosis and fix
The Selective Catalytic Reduction (SCR) system on 2015-2022 6.7L Power Stroke trucks - which uses Diesel Exhaust Fluid (DEF) to reduce NOx emissions - is prone to failure, most commonly triggering DTC codes P207F (Reductant Quality Performance) and P20EE (SCR NOx Catalyst Efficiency Below Threshold). Causes include degraded or crystallized DEF fluid (DEF has a shelf life of 1-2 years and degrades faster in heat), a failed DEF injector, SCR catalyst failure, DEF quality sensor failure, or NOx sensor failure. In limp mode, the truck's performance is severely limited. The system is complex and diagnosis requires a professional scan tool. The DEF injector is a particularly common failure point on 2017+ trucks.
Common Symptoms
- Check engine light with P207F (Reductant Quality Performance) code
- Check engine light with P20EE (SCR NOx Catalyst Efficiency Below Threshold)
- Reduced engine power / limp mode
- DEF gauge or warning light showing issue
- Truck will not restart after excessive limp mode cycles
- Rough running at idle
- Increased fuel consumption
How to Fix
Diagnose with Ford IDS or quality OBDII scanner capable of reading all PCM codes. Common fixes: (1) Drain and refill DEF tank with fresh fluid (AutoZone DEF, Ford Motorcraft DEF VC-10-B) - $15-$30. (2) Replace DEF quality sensor ($150-$300). (3) Replace DEF injector ($300-$600 + labor). (4) SCR catalyst replacement ($2,000-$4,000). Always use fresh, quality-brand DEF (avoid bargain/store-brand DEF). Do not let DEF tank run to empty repeatedly.
Sources for this issue (1)
EcoBlue diesel Transits have documented owner reports of check engine lights and emissions system warnings related to SCR/DEF operation, commonly tied to NOx sensor faults or SCR efficiency monitoring. When the system detects persistent faults, it may trigger reduced power or countdown-to-no-start strategies depending on market/calibration. These issues are frequently accompanied by emissions-related DTCs and can be intermittent before becoming persistent.
Common Symptoms
- Check engine light with emissions warnings
- Reduced power / limp mode
- DEF/SCR warning messages
- Increased DEF consumption or abnormal dosing behavior
- Potential countdown-to-no-start (market dependent)
How to Fix
Diagnose SCR system with a capable scan tool, verify DEF quality, check wiring/connectors at NOx sensors, and replace failed NOx sensor(s) as indicated; perform required resets/adaptations. If applicable per Ford service guidance, update PCM calibration addressing false SCR/NOx diagnostics and confirm proper dosing operation.
Sources for this issue (1)
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 Ford?
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 Ford it is documented across 2 models: F-250 Super Duty, Transit.
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 Ford?
Published repair estimates on Ford range from $350 to $4,500 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.