AdBlue / DEF warning light (diesel): what it means.
A diesel with an exhaust-cleaning system uses a fluid called AdBlue (also called DEF) and it is running low, or there is a fault in that system.
Can I keep driving?
You can drive for now, but top up soon. If the tank runs fully empty, many diesels won’t restart once switched off.
What to do
Check the message on the dashboard: it usually says how many miles you have left.
Top up with AdBlue or DEF from a fuel station or car shop. Use only that product, and never put it in the fuel tank.
The filler is usually next to the fuel cap or in the trunk. Check your manual.
If the light stays on after a top-up, a workshop needs to check the system.
General guidance, not a diagnosis. Warning lights vary between cars, so check your owner's manual too. If you're ever unsure or the car feels wrong, stop and call for help.