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OBD-II · Engine and powertrain (P)

P2BAA

NOx exceedance - low AdBlue consumption

What it means

NOx emissions may exceed limits because the car is using less AdBlue than it should, meaning dosing is not reaching the exhaust. 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
01blocked or crystallised dosing injector
02weak pump or blocked filter
03leak in the AdBlue line
04tank level sensor misreading

What to check, step by step

  1. 01Inspect the dosing injector and lines for crystals and leaks.
  2. 02Run a dosing quantity test with a diagnostic tool.
  3. 03Check pump pressure and the tank filter.