OBD-II code · Powertrain (generic, extended)
P2BAC NOx Exceedence - Insufficient Reagent Quality
The diesel exhaust aftertreatment system detects elevated NOx levels combined with abnormal reagent (AdBlue/DEF) consumption, indicating that the reagent quality is insufficient or contaminated. Many regions trigger driver inducement (limited restarts).
Is it safe to drive with P2BAC?
The car may go into limp mode (reduced power). Get it diagnosed before a long trip.
Common causes
- Most likelyNon-DEF liquid in tank (water, diesel)
- PossibleAged or diluted DEF/AdBlue
Symptoms
- Check engine light or NOx warning on
- AdBlue/DEF level or quality warning
- Possible no-start countdown after ignore period
- Failed emissions inspection (NOx)
Repair at a glance
- Difficulty
- Hard
- DIY friendly
- Best left to a mechanic
- Typical labour
- 1–6 h
- Emissions test
- Likely to fail
- After the fix
- A drive cycle is needed before the light stays off
- Parts involved
- Scr Catalyst, Def Tank, Nox Sensor, Def Quality Sensor
Related codes
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.