Each and every day there are more cars on our roads that are equipped with SCR aftertreatment system requiring AdBlue addictive. The aqueous urea solution used in them, because that’s what the liquid hiding under this trade name is, helps neutralize nitrogen oxides in exhaust gases. That makes the questions what may cause light to stay on after topping off AdBlue solution, which is asked more often by the drivers.
AdBlue then and now
Not that long ago, especially in passenger vehicles, it was rarely required to tank AdBlue. The reason for that is because car producers configured their aftertreatment systems in the way they worked, mostly during official tests and not regular exploration. After so called “dieselgate” car producers started configuring their Selective Catalytic Reduction (SCR) to actually serve its purpose. Therefore, along with tightening emission standards, usage of AdBlue increased in passenger cars.
AdBlue refill notice
During driving to the hot catalytic converter, AdBlue liquid is being injected which, in the course of chemical reactions, converts nitrogen oxides found in the exhaust gas into nitrogen and water vapor (H2O + N). What shouldn’t surprise, along with distance driven, the amount of urea solution is getting smaller in the tank.
In modern cars with SCR catalytic, one of the features is a system for controlling this fluid. It informs about urea level and possible faults of the same system. The AdBlue indicator light is on to inform you that the fluid is running out and how many miles you have left to drive.
Are you low on AdBlue? You may not start the engine.
If, despite the messages that appear, the amount of AdBlue is not refilled, you may be in for an unpleasant surprise. When you run out of fluid in the tank, driving can still continue, but only until you turn off the engine. After that, it will no longer be possible to start it. Such an interlock is related to the current standards and is intended to prevent us drivers from driving a vehicle that does not meet them. Because of the lack of AdBlue fluid, is also the inability of the catalytic converter to neutralize nitrogen oxides.
What to do when the AdBlue light does not go off after refilling?
A low AdBlue message is not usually a big obstacle to continuing your journey. All you have to do is stop at a station and refill the fluid level in the tank, which is usually located next to the fuel filler. Then, in order for the SID321 controller to read the refill and erase the message, turn on the ignition, but do not start the engine. Wait for about 30-40 seconds while the ignition is on. Skipping this procedure may cause the AdBlue light to remain on.
If the AdBlue light continues to indicate an error despite the above steps, it may be a malfunction in the exhaust aftertreatment system itself, which is difficult to fix in the classic way. Often the culprit is faulty software, a malfunction in the NOx sensor or the AdBlue pump. This is a more worrisome scenario involving additional expenses. The cost of new software is about 70–120 euros, while a new sensor can cost several hundred euros, and the AdBlue pump is even more expensive….
A list of symptoms accompanying the AdBlue light:
- Message about adding AdBlue, despite full tank
- Countdown of kilometers to vehicle immobilization
- Limited power
- Low AdBlue pump pressure
- Limited speed
- “Check engine” light and engine failure messages
- Malfunctioning NOx sensors that cause errors to appear and disappear on their own.
How to fix the malfunction?
Fortunately, we have a proprietary solution that will help you save money on purchasing parts that are often faulty and hard to find. If you’d like us to help solve your problem, contact us or one of our partner garages.
Header photo – image by Freepik.