P20EE SCR NOx catalyst efficiency below threshold (bank 1)
What P20EE means
Diesels with selective catalytic reduction (SCR) inject AdBlue into the exhaust to convert NOx into nitrogen and water. P20EE means the NOx sensors show the catalyst is not reducing NOx as much as it should. If it is not fixed, many cars start a countdown that limits power or prevents restarting.
P20EE is a generic SAE J2012 code: it means the same on every make. The exact cause still depends on the car, so read the freeze-frame data before replacing parts.
At a glance
- Severity
- Medium
- Typical repair cost
- 400–3500 €
- Workshop time
- 1.5–6 h
- Repair difficulty
- Hard
- DIY possible
- No
- Check engine light
- Yes
- Affects emissions test
- Yes
Parts and labour at an independent workshop in Europe. Main dealers charge more; the cause decides the bill, not the code.
Symptoms
- Check engine or AdBlue warning light
- Countdown warning for restricted starts
- Reduced power in some cases
- Technical inspection failure for NOx
Common causes
- Contaminated, diluted or old AdBlue
- Blocked or faulty AdBlue dosing injector
- Faulty upstream or downstream NOx sensor
- Exhaust leak before or after the SCR catalyst
- Worn or contaminated SCR catalyst
Can I keep driving with P20EE?
You can drive, but have it checked within one or two weeks. Watch for an AdBlue countdown message; if it appears, the car may not restart once it reaches zero.
What to check first
- Check AdBlue quality with a refractometer and replace it if diluted or contaminated
- Run a dosing test to check the quantity delivered by the AdBlue injector
- Compare upstream and downstream NOx sensor readings
- Check for exhaust leaks before considering SCR catalyst replacement
Related codes
- P2101 Throttle actuator control motor circuit range/performance
- P2099 Post-catalyst fuel trim system too rich (bank 2)
- P2098 Post-catalyst fuel trim system too lean (bank 2)
- P2097 Post-catalyst fuel trim system too rich (bank 1)
- P2096 Post-catalyst fuel trim system too lean (bank 1)
- P218F Reductant (AdBlue) no flow detected
- P203B Reductant (AdBlue) level sensor A circuit range/performance
- P2017 Intake manifold runner position sensor/switch circuit high (bank 1)
Data: TORKO fault-code catalogue, built on OBDex (CC0-1.0) and reviewed against workshop practice. Informational only — it does not replace a diagnosis by a mechanic.
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