OBD-II code · Powertrain (generic, extended)
P2BA9 NOx Exceedence — Insufficient Reagent
The SCR system has detected that NOx emissions exceed the legal limit and the cause is traced to insufficient AdBlue/DEF dosing. Modern emission regulations require this fault to be reported separately so that operator-induced misuse (running an empty tank, diluting the fluid) is recorded.
Is it safe to drive with P2BA9?
The car may go into limp mode (reduced power). Get it diagnosed before a long trip.
Common causes
- Most likelyDEF tank repeatedly run empty
- PossibleDiluted or contaminated DEF
- PossibleDosing pump output below spec
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
- Medium
- DIY friendly
- Best left to a mechanic
- Typical labour
- 1–4 h
- Emissions test
- Likely to fail
- After the fix
- A drive cycle is needed before the light stays off
- Parts involved
- Reductant Dosing Unit, Reductant Tank, Scr Catalyst
Related codes
- P2BA6NOx Exceedance - SCR NOx Catalyst Performance
- P2BA7NOx Exceedence - Empty Reagent Tank
- P2BA8NOx Exceedence - Interruption of Reagent Dosing Activity
- P2BAANOx Sensor Range/Performance (Bank 1, Sensor 1)
- P2BABNOx Exceedence — Reagent System Performance
- P2BACNOx Exceedence - Insufficient Reagent Quality
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.