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Frequently asked questions about cars and motorcycles

How the AdBlue System Works

Model: (Various brands) Various
Part: AdBlue warning light

This video explains how the AdBlue system works: there are 4 components: the pump, the tank, the NOX sensor, and the injector. The pump maintains pressure in the AdBlue system, drawing from the tank at around 5 bar. It pushes towards the injector, sending it directly to the exhaust, before the catalyst; the engine is located elsewhere. After the catalyst, we have the NOX sensor, which communicates with the engine control unit and the AdBlue pump. That’s the entire system. The biggest issue with this liquid is crystallisation, which forms crystals and becomes hard. This is detrimental to the system, blocking the NOX sensor, which detects that the additive is not being injected and informs the engine control unit, putting the vehicle into protection mode. To keep the system efficient, always maintain the AdBlue tank at the correct level to prevent crystallisation.

Updated on 21 August 2026 by ScegliAuto

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