Mobile Auto Electrician | BMW Specialist | BMW Coding | BMW FRM Repair | ECU Repair | ECU Replacement |BCM Repair | Immobiliser Repair | Instrument Cluster Repair

Diesel produces lots of soot that may cause respiratory issues and contribute to the potential risk of heart disease. Modern diesel vehicles must be fitted with a Diesel Particulate Filter in the exhaust to stop this soot passing into the atmosphere. The purpose is an 80% cut in particle emissions, but the technology's not without problems and our patrols are frequently called to vehicles with a blocked DPF. To maintain performance, a DPF has to be emptied regularly. This is usually done passively in a process called regeneration, which activates when the exhaust temperature is high enough when driving on highways or fast roads, for example.

 

Many vehicles do not get the right kind of use for passive regeneration to work, so the Engine Control Unit software detects with the help of Lambda Sensor that the filter getting blocked and injects extra fuel into the engine to increase the exhaust temperature and to trigger regeneration. Active regeneration will be started every 300 miles or so, depending on how you use your vehicle and will take 5 to ten minutes to complete while you are driving. Problems occur if your journey is too short and the regeneration doesn't finish. Receive a warning light showing that the Diesel Particulate Filter is blocked. It should be possible to complete an active regeneration cycle and clear the warning light by driving for ten minutes or so at the speeds of over 60mph.

 

If you ignore a DPF warning light and keep driving in a relatively slow, stop/start pattern, soot will build up in the Diesel Particulate Filter until your car goes into restricted performance mode to prevent damage. You will have to get a car garage to do a manual or forced filter regeneration. In extreme cases, they might have to replace the filter that could cost as much as £1000, plus labour. In many cases, there is only a short time between the DPF is partially blocked and it getting so blocked. It needs a manual regeneration.

 

If you're buying a new car and plan to use it more for town-based, stop/start driving, you'd be wise to avoid diesel fitted with a diesel particulate filter.  Even if your driving isn't mainly urban stop/start, you may need to change your driving style to keep the system running properly.