AdBlue warning light: fill up before it reaches zero
Top the AdBlue up before the level reaches zero. If the tank runs completely dry, many cars refuse to restart, and by then topping up at the roadside does not help.
Can you keep driving?
Yes, but the car is counting down the miles to a no-start.
What the warning actually means
AdBlue, sold as DEF in some markets, cleans nitrogen oxides out of the exhaust on diesels from roughly 2015 onward. The system is a legal requirement, and the car is programmed to stop you if it runs out.
Common causes
- Normal consumption. The tank is meant to be topped up
- A faulty level sensor or dosing pump
- Crystallised AdBlue after a long period standing
What to do now
- Buy AdBlue at a filling station or a parts dealer.
- Fill the tank with the blue cap, often next to the diesel filler.
- Drive a little, and check that the countdown resets.
What people often get wrong
That it is enough to fill up when the tank is empty. If it runs completely dry, many cars refuse to start, and having the bottle in the boot does not help then.
When the car must go to a workshop
If the warning does not clear after filling, or the countdown is already low, book an appointment immediately.
Read next
- DPF light on: drive, do not park
- Glow plug light on a diesel: wait until it goes out
- Your check engine light isn't random
This page is general information and does not replace a professional assessment. Symbols, codes and behaviour vary between makes. Always check the handbook for your own car.
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