AdBlue Warning Light: Causes, Symptoms and Solutions

What Does an AdBlue Warning Light Mean?

An AdBlue warning light indicates that the vehicle’s Selective Catalytic Reduction (SCR) emissions system has detected a condition that requires attention. Depending on the manufacturer and fault type, the warning may appear as a simple dashboard light, a text message, or a countdown warning advising that the vehicle may eventually be prevented from starting.

The SCR system is designed to reduce harmful nitrogen oxide (NOx) emissions by injecting AdBlue fluid into the exhaust system. When the system detects a problem, it stores a fault code and alerts the driver.

Common causes include low AdBlue levels, poor AdBlue quality, crystallised deposits within the system, NOx sensor faults, AdBlue injector issues and SCR efficiency problems.

Ignoring an AdBlue warning can lead to further fault messages, reduced engine performance and, in some vehicles, a no-start countdown that limits operation until the underlying issue has been resolved.