AdBlue / urea warning light: what to do

On diesel vehicles equipped with selective catalytic reduction (SCR), AdBlue (urea solution) is injected into the exhaust to reduce nitrogen oxides. When the AdBlue warning light comes on, you need to act to avoid power limitation or vehicle immobilisation.

Light on: common causes

Low level: the AdBlue tank is empty or below the threshold. Fluid quality: non-compliant or diluted AdBlue may be rejected by the ECU. AdBlue injector clogged or faulty. Level sensor or consumption calculation faulty. Cap or filler not properly closed (emissions rejected by ECU in some cases).

What to do

As soon as the warning (message or light) appears, top up the AdBlue tank with compliant fluid (ISO 22241 or equivalent). Use a clean container and avoid contamination (fuel, water, dirt). After filling, it may be necessary to reset the counter or drive a few kilometres for the light to go out. If the light stays on or comes back quickly, have the injector and circuit checked by a professional.

Risk of power limitation

On many models, if the level remains insufficient after a given period and number of kilometres, power is limited or the vehicle will not restart. Check the handbook for the exact deadline and do not wait until the last minute to top up.

Order of magnitude for costs

AdBlue (container): €15–40. AdBlue injector: €200–600 and more depending on vehicle. AdBlue pump: €300–800. Sensor: €100–300. My Auto Check-up helps you describe symptoms for an initial estimate before visiting the garage.