Powertrain, generic (extended)

P2BA6 NOx Exceedance - SCR NOx Catalyst Performance

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

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.

Likely causes

SCR catalyst aged, overheated or chemically poisoned
Urea crystal deposits on mixer or catalyst face
Downstream NOx sensor drifting high
Too little NO2 from upstream oxidation catalyst

Symptoms

  • 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

Repair estimate

DifficultyHardWorkshop job
Parts and labour€300–4,000
Time1–6 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

scr catalystreductant dosing unitnox sensor

Related codes

P20EEP2BADP2BA9P2BAEP2BA4

References: legislation.gov.uk, law.cornell.edu, patents.google.com.