P2BA6NOx Exceedance - SCR NOx Catalyst Performance
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- P2BA6 opens the group of NOx exceedance codes that grew out of the European rules on reagent-based NOx control. Each code names why tailpipe NOx has climbed above the diagnostic limit; here the blame lies with the SCR catalyst itself, while dosing, reagent and EGR still look plausible. Regulation (EU) 2017/1151 Annex XVI lets makers use exhaust NOx sensors to detect such excess, with the warning and inducement chain that follows. CARB separately asks for SCR conversion monitoring, usually reported as P20EE. FEV describes a test that tells a weak catalyst apart from poor feed gas. No maker documents P2BA6 publicly. Expect the MIL and an emissions warning; if not fixed, speed or restart limits may follow.
- What you may notice
- MIL and emission system warning in the cluster
- Countdown to speed limit or no restart after some distance
- Higher DEF consumption without better NOx reduction
- Likely causes
- LikelySCR catalyst aged, overheated or chemically poisoned
- PossibleUrea crystal deposits on mixer or catalyst face
- PossibleDownstream NOx sensor drifting high
- RareToo little NO2 from upstream oxidation catalyst
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €300 – €4,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.