P2BAD
NOx Exceedence - Insufficient Reagent Consumption
The aftertreatment system detects elevated NOx emissions while reagent (AdBlue/DEF) consumption is below the expected level. Causes include clogged dosing injector, incorrect dosing rate or tampering.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: hard
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)
Common causes
Ordered by how often each turns out to be the cause.
- Clogged DEF dosing valveCommon
- Incorrect dosing calibrationPossible
Parts involved
- Def Dosing Valve
- SCR Catalyst
- NOX Sensor
P2BAD is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.