OBD-II code · Powertrain (generic, extended)
P2BAB NOx Exceedence — Reagent System Performance
The SCR system has detected that NOx emissions exceed the legal limit and the cause is traced to a performance fault in the reagent dosing system — for example a slow dosing pump, a clogged injector, or a frozen line that is not yet caught by another DTC.
Is it safe to drive with P2BAB?
The car may go into limp mode (reduced power). Get it diagnosed before a long trip.
Common causes
- Most likelyReductant injector clogged with crystals
- PossibleDosing pump output below spec
- PossibleReagent supply line blocked
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
- 1–5 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 Injector, Reductant Pump
Related codes
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.