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OBD-II · Engine and powertrain (P)

P2BAE

NOx exceedance - NOx control monitoring system

What it means

NOx emissions cannot be confirmed within limits because the system that monitors NOx control is not working, typically due to a NOx sensor or related fault. On vehicles with SCR, a confirmed unresolved fault may trigger reduced performance or a no-restart countdown; follow the displayed warning and the vehicle handbook.

Symptoms

  • emissions warning; an AdBlue no-start countdown may appear on SCR-equipped vehicles
  • engine warning light
  • if a no-start countdown is displayed, restarting is inhibited when it reaches zero

Likely causes, most likely first

Likely causes, most likely first
No.Cause
01failed NOx sensor
02NOx sensor wiring or power supply fault
03other SCR system fault preventing monitoring

What to check, step by step

  1. 01Read NOx sensor codes and live data.
  2. 02Check NOx sensor power, ground and connectors.
  3. 03Diagnose the primary fault preventing NOx monitoring; replace a NOx sensor only if its tests confirm failure, then complete required initialization and the OEM validation cycle.