What is AdBlue (SCR)?

AdBlue was introduced on many newer diesel engines to help meet modern emissions regulations. It is used as part of an SCR system, which stands for Selective Catalytic Reduction.

SCR works by injecting a urea based fluid (AdBlue) into the exhaust. This creates ammonia inside the exhaust stream, which helps the catalyst convert NOx (nitrogen oxides) into harmless gases. It is technology that has been used in commercial vehicles for many years before becoming common on passenger cars.

How does it relate to DPF and regenerations?

AdBlue and SCR reduce NOx further, which forms part of the overall emissions strategy alongside EGR and the DPF system. Depending on the vehicle, this can help the ECU keep emissions within limits and can influence how often the car needs to regenerate the DPF.

Why do AdBlue systems cause problems?

AdBlue systems can be complex and faults are often expensive to diagnose and repair. Common issues include:

• AdBlue crystallisation in lines or injectors

• Injector failures

• Wiring and sensor faults

• Countdown warnings that appear even when the root cause is not obvious

On many vehicles, once an SCR fault is detected the ECU can start a countdown to a no start condition. When the counter reaches zero, the vehicle will be prevented from starting even though the engine itself may be mechanically fine.

What does the AdBlue solution do?

An AdBlue solution disables SCR functions in the ECU and removes the associated fault codes. This can stop the countdown behaviour and prevent SCR related no start conditions.

Always ensure you understand and comply with the regulations in your country or region before applying any emissions related modifications.