What does the AdBlue warning light (low level, no restart, malfunction) mean?

An AdBlue warning light usually means that the diesel engine exhaust fluid level is low, which will eventually prevent the engine from starting.

Until now, diesel engines have typically been reserved for trucks and larger, heavier vehicles. However, due to the high efficiency of diesel fuel these days, it has become much more common in small passenger cars. This high efficiency is due to the fact that diesel, by its nature, contains more potential energy than conventional gasoline. Along with the extra energy, diesel engines have a higher compression ratio, which allows them to extract more total energy from the fuel than a conventional gasoline engine.

However, this high efficiency comes at a price in terms of additional exhaust emissions. To help the catalytic converter break down harmful gases, diesel exhaust fluid is slowly injected into the exhaust pipe. The liquid evaporates, and, getting into the catalytic converter, nitrogen oxides decompose into harmless water and nitrogen. One of the most common diesel exhaust systems is AdBlue, which can be found in American, European and Japanese vehicles.

What does the AdBlue warning light mean?

The AdBlue system has a pump that injects a small amount of diesel exhaust fluid depending on engine operating conditions. A small tank with a liquid level sensor stores liquid, so frequent topping up is not required.

There are three lights on the dashboard that may come on to alert you to any problems with the AdBlue system. The first light is the low level warning light. It should turn on long before the tank is completely empty so that you have enough time to fill it up. This indicator is usually yellow, and after you fill the tank with exhaust fluid, it should turn off. If you don't fill up the tank, it will eventually turn red, which is a warning that you can't restart.

When this indicator is red, you will not be able to restart the engine after it has been turned off. If this happens while driving, refuel your car immediately to top up the tank, otherwise you won't be able to start the engine again. This feature is designed to prevent drivers from traveling long distances without exhaust fluid. Again, topping up the tank should turn off the lights.

Finally, if the computer detects any faults in the system, the service engine light will come on along with a fluid level warning. This may indicate a problem with the delivery system or fluid level sensor, or it may indicate that the wrong fluid is being used. You will need a diagnostic scanner to read the error code and understand what is going on. Do not ignore this indicator, as using the wrong type of fluid may permanently damage the system.

Is it safe to drive with the AdBlue light on?

While this indicator does not indicate a safety issue, ignoring the warning will ultimately prevent you from starting the engine. When you see a low fluid warning, you still have plenty of time before topping up becomes absolutely necessary. Don't forget this or you may run out of fluid and risk getting stranded.

If any of the AdBlue lights are on, our certified technicians will help you fill the tank or diagnose any problems you may be having.