This section briefly explains a cars NOx Catalyst/SCR System, and how we can help if yours is giving issues. Click the below for some basic background, or use the tabs further down to find out how we can help.
SCR (Selective Catalytic Reduction) Systems
SCR is a method of removing Nitrogen Oxides (NOx) from the exhaust. This is done by converting NOx by use of a catalyst with an additive fluid, into diatomic nitrogen and water and sometimes carbon dioxide. (N
2 , H
2O and CO
2) The system is very sensitive and when not functioning correctly can create highly toxic exhaust fumes.
SCR Systems have their limitations, some of the most common problems we find are detailed below:-
–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 any Engine Malfunctions, but may still occur naturally.
–Vehicle Driving. SCR Systems work best in high temperatures. Driving at lower speeds or not driving longer distances on a daily basis can lead to the the additive fluid not completing its reaction, causing the catalyst to degrade.
-Incorrect Additive In most vehicles an additive is required for the SCR process. If the car is ran empty of fluid or the wrong additive is used it will degrade the catalyst and damage the injection system.
Due to the sensitive and problematic nature of the SCR Systems, we recommend an advanced diagnostic before committing to a removal. Usually issues are fixable, however parts are expensive so weighing up all options is recommended. If removal is the best option, there are two methods – vehicle dependent :-
- Software – remapping the vehicle to remove the SCR software from the ECU.
- Hardware – how we stop the SCR Process. This is vehicle and fault dependant. Sometimes the software is enough to stop the process, or a electrical plug may need to be removed from a control module.