If the reading is too high (or is lower than usual), the SCR system will respond by releasing more (or less) urea based on the information provided by the sensor. Most NOx sensors function by initially removing oxygen before breaking down the nitrogen oxides to create a reading. The greater the level of NOx, the stronger the voltage. A voltage is then passed through an electrolyte, and this determines how much NOx is present in the vehicle’s system.
This is done via a working electrode which features a material that reacts with NOx. The NOx sensor detects nitrogen oxides via an electro-catalytic mechanism. If you own a diesel-powered car, the NOx sensor is critical to the SCR system to ensure your vehicle is compliant. If too much NOx is detected, the sensor will feed this information to the SCR system, which can then adjust its output accordingly so that the vehicle continues to meet emissions regulations. With emissions regulations for diesel vehicles becoming more stringent, SCR systems contain a NOx sensor, which monitors the amount of nitrogen oxides being released into the air by a vehicle. If your SCR system is not working, your vehicle could fail its MOT.
With carbon neutrality becoming a major issue around the world, many governments insist that diesel vehicles must feature an AdBlue SCR system to be compliant with the law on emissions. SCR technology is a cost-effective and fuel-efficient means to help reduce diesel emissions. The sensor probe on a NOx unit is universal and fits many different car models. It’s not something that many manufacturers will advertise in an obvious manner, but many of the world’s largest car manufacturers (including Audi, Volkswagen, Peugeot, Jaguar, Citroen, and Mercedes) all make use of AdBlue technology. If you drive a newer diesel vehicle, it’s likely that it comes with AdBlue technology as standard. When this fluid is released, it creates a chemical reaction which converts nitrogen oxide into harmless nitrogen, water, and carbon dioxide, before it is expelled via the exhaust tailpipe of a vehicle. The source of reduction is typically automotive-grade urea, which is also known as Diesel Exhaust Fluid. AdBlue’s SCR system is an advanced emission control technology which injects a liquid reducing agent via a special catalyst in the exhaust stream of an engine.