The EGR valve or exhaust gas recirculation system forms part of the system to combat emissions and increase engine efficiency by recirculating air back into the car engine. EGR valve problems may result from a build-up of carbon and toxins from car emissions.
Cleaning is relatively simple and straightforward. You can use a special cleaner to remove the build-up of carbon. If faulty, this would cause your vehicle to fail its emissions test so it is important to get it replaced as they are a legal requirement for vehicles in the UK.