AdBlue warning: what to do and what happens at zero
Updated:
The AdBlue warning means AdBlue is running low or there is a fault in the SCR system. When the range countdown reaches zero, the car won't let the engine restart after you switch it off. The engine does not stop while driving. Top up early. If the warning stays on after filling, the fault may be a sensor, the tank heater or the pump.
What is AdBlue?
AdBlue is a urea solution sprayed into the diesel exhaust ahead of the SCR catalyst. It turns nitrogen oxides into nitrogen and water. Consumption depends on the engine and driving, on a car typically about 1–2 litres per 1000 km, more on some cars.
How to top up AdBlue
The AdBlue filler is usually next to the fuel filler with a blue cap, or in the boot. Use only AdBlue marked ISO 22241, never water or anything else.
Never put AdBlue in the fuel tank. If it happens, don't start the engine; call a workshop or breakdown service, as the fuel system has to be drained and flushed.
After filling, some cars clear the warning at once, others after a short drive. Some need a minimum amount added in one go.
Warning stays on after filling
Then the fault is in the system: the level or quality sensor, the tank heater, the pump, the injector or the NOx sensor. In winter frozen or crystallised AdBlue is a common cause. AdBlue freezes at about -11 °C, which is why the tank is heated.
We read the codes and look at live data. Sometimes cleaning the injector is enough, sometimes a sensor or the tank module has to be replaced.
Want a definite answer?
Bring the car to our workshop in Estonia for diagnostics. We read the fault codes, test the sensors and tell you what is wrong.
Frequently asked questions
Can you drive with the AdBlue warning on?
Yes, while the display still shows range. Top up at the first chance. At zero the car won't restart after you switch it off.
What happens if AdBlue runs out?
The engine doesn't stop while driving, but after you switch off, the car won't restart until AdBlue has been added.
Does AdBlue freeze?
Yes, at about -11 °C. The tank has a heater that thaws it. If the heater fails, you get a warning in winter.
Can the AdBlue system be switched off?
No. It is an emissions control system and removing it is illegal. We don't do that work.
How much does a diagnosis cost?
Diagnostics cost €45/h, the price depends on the job. Sensor or tank module prices depend on the car.