NOx/Adblue/SCR/ DTC Removal

SCR (Selective Catalytic Reduction) / NOx Systems

What is SCR?

SCR is a method of removing Nitrogen Oxides (NOx) from the exhaust stream. Using a catalyst and an additive fluid (such as AdBlue), NOx is converted into diatomic nitrogen and water and sometimes carbon dioxide (N₂, H₂O and CO₂). The system is very sensitive and, when not functioning correctly, can result in highly toxic exhaust fumes.

What causes SCR issues?

Some of the most common causes of SCR problems include:

• Contamination: fine particles in exhaust fumes, as well as ammonia, sulphur and silicone compounds, can naturally block the SCR catalyst. This can be accelerated by existing engine malfunctions.
• Driving profile: SCR systems work best at higher exhaust temperatures. Short trips, low-speed driving and not regularly driving longer distances can prevent the additive fluid from completing its reaction, causing the catalyst to degrade.
• Incorrect or empty additive: running the vehicle with no fluid or using the wrong additive can degrade the catalyst and damage the injection system.

What are my solutions to an SCR problem?

Because SCR systems are sensitive and components can be expensive, we always recommend an advanced diagnostic before committing to any removal or major repair. Many issues are repairable, but the cost of parts versus software-based options should be carefully weighed.

If removal is the best option, there are two core methods:

• Software approach: remapping the ECU to remove or modify the SCR-related control logic, preventing the system from triggering faults or countdowns.
• Hardware approach: stopping the SCR process at a component level. Depending on the vehicle and specific fault, this may involve leaving components disconnected or modifying the system's control wiring or modules.

DTC Removal / Engine Management

What are Engine Management Lights?

Engine Management Lights are designed to alert the driver when a fault has occurred within the engine management system. Your vehicle handbook is the best reference for what each specific light means and which system it relates to.

Engine management covers engine-related faults only. Other systems such as ABS, airbags, gearbox and chassis electronics are separate and will often have their own warning lights and diagnostics.

What are my solutions to a warning light?

The first step is always proper diagnostics. This means plugging the car in, reading the codes, and recording the exact fault information. A printed report or a clear picture on a smartphone is ideal — guessing the codes later wastes time and money.

With accurate diagnostic information we can advise on the next step. On some engine systems, certain non-critical faults can be removed from the ECU if they do not affect safety or emissions. For example:

Important notes:

• This approach applies only to the engine management system. Airbag, ABS, stability control and similar safety systems cannot be treated in this way.
• If we deem a fault “unethical” to remove — for example, it compromises safety or emissions — we simply will not carry out that work.
• DTC removal work carried out by Auto-tune is guaranteed for as long as you own the vehicle, in line with our terms and conditions.