Mercedes Repair Questions? Ask a Mechanic for Answers ASAP
Hello and Welcome! I'm Billy and i will assist you with your inquiry. Feel free to ask if any further info is needed.If you get prompted for a Premium service or a phone call, please ignore that, as i don't think it is needed at this point.
My apologies for the delay, thank you for your patience.
If you would please get back to me with your exact Mercedes model and the engine you have on, it would be great in case we need to check diagrams or instructions.
As for now, on many Mercedes models the Adblue level sensor is known to get faulty and cause this problem. The light would come one, you add the liquid, the sensor is stuck the control module thinks that no liquid is present.
The way to sort this would be connecting a scan tool and resetting the system. If the problem persists then fault codes will be stored. I can explain those fault codes, tell you what to check and how to check it in order to fix or replace the faulty part (most commonly the sensor).
However, we might not get to that, as usually a reset (unfortunately only available through a scan tool) would fix the problem.
To shed more light on this matter:
As the problem is so common, companies have started making emulators that fit in place of the sensor. You wouldn't need to put Adblue anymore. However, this is wrong environmentally and illegal.
Kindly let me know if you need more information on the matter. And please remember that you can get back to me on this page in case the problem persists and fault codes are present. I will be more than glad to explain their meanings and provide guidance on the diagnostics to prevent replacing unneeded parts.