OBD-II Code
P20EE
Severity
Not yet reviewed
Nobody on our side has assessed this code yet, so we are not going to guess at how serious it is.
Can you drive it
We cannot say
Treat it as unknown until a shop reads it with live data. If the check-engine light is FLASHING, stop driving as soon as it is safe to — that means an active misfire, whatever the code.
Indicative cost (USD)
$380–$3,800
From this code's diagnostic notes. Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
P20EE means the SCR NOx catalyst on Bank 1 is converting less NOx than the ECM's efficiency model requires - it is the catalyst-level efficiency code, distinct from quality (P207F) or dosing (P204F) faults.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then follow the diagnostic notes further down this page, in the order they are written.
They are written in the order a shop works this code, cheapest checks first. Where they name a component, inspect its wiring and connector before replacing it.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Check engine light
Read the full diagnostic procedureP20EE means the SCR NOx catalyst on Bank 1 is converting less NOx than the ECM's efficiency model requires - it is the catalyst-level efficiency code…
P20EE means the SCR NOx catalyst on Bank 1 is converting less NOx than the ECM's efficiency model requires - it is the catalyst-level efficiency code, distinct from quality (P207F) or dosing (P204F) faults.
Cheapest-first ladder
- this is the single most over-condemned code on modern diesels, so work the ladder honestly.
- First refractometer the DEF, then verify upstream NOx sensor reads 200 to 600 ppm under cruise and downstream reads under 50 ppm; if downstream is reading 150+ ppm with good DEF and verified dosing, the SCR catalyst may genuinely be aged.
- Before condemning the cat, swap or test both NOx sensors (they fail more often than the catalyst by roughly 4 to 1).
- Caveat: a $3,500 catalyst replacement on a $400 sensor fault is the most expensive mistake on this code.
Vehicle-specific patterns2011 to 2016 Duramax LML set P20EE constantly from failed downstream NOx sensor 2, GM bulletin PI1149 explicitly says to replace the sensor before th…
- 2011to 2016 Duramax LML set P20EE constantly from failed downstream NOx sensor 2, GM bulletin PI1149 explicitly says to replace the sensor before the SCR;
- 2011to 2014 Ford 6.7L Powerstroke throw P20EE from sulfur poisoning after extended idle, Ford TSB 13-7-15;
- 2010to 2016 Mercedes Sprinter OM642/OM651 BlueTEC set P20EE from cracked SCR substrate after repeated DEF crystallization events;
- 2009to 2014 VW/Audi 3.0 TDI set the code from genuinely aged SCR catalysts at 120,000+ miles.
Estimated repair$380 to $3,800.
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