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Posted by Elizabeth Davis on

Like all new diesel cars manufactured since 2008, BMW have had to fit DPF (Diesel Particle Filters) to all its diesel vehicles, in fact it started to fit them as early as 2005 / 6 on some models.

The idea of the DPF is to trap soot particles, from leaving the exhaust system in order to comply with stricter EU4 and EU5 Emissions. When the filter becomes blocked, a regeneration program is triggered by the vehicle ECU, whereupon the DPF Filter is superheated to over 600C and the accumulation of soot is then burned off,  fairly harmlessly as CO2 gas. In order to trigger the regeneration process the car has to be traveling a high speed for a reasonable period of time, such as down a motorway or dual carriageway.

Problems with DPF’s begin, on diesel cars fitted with DPF’s which are only used for short or infrequent trips and of which rarely see high speed prolonged motorway journeys. Short urban trips often result in DPF’s becoming blocked far quickly and more frequently and the regeneration process isn’t able to trigger, or worse still, is abandoned part way through a process.

This results in the DPF eventually becoming clogged, and the orange indicator on the dashboard will illuminate to inform you that there is a problem with the DPF system and that the DPF is no longer working correctly, this warning light generally illuminates when the DPF is around 70% blocked.

If you have this indicator illuminated on the Dashboard, then you need to plan a fast trip down the motorway, ideally at high rev’s for at least 30 minutes or so, this will enable the ECU to trigger the DPF regeneration process, and the soot should then be adequately burned off, the light will extinguish and all should then be well.

Unfortunately, depending on the level of blockage, the period of time which has elapsed since the orange DPF warning light began illuminating and the age of the DPF itself, sometimes a delayed DPF regeneration doesn’t solve the problem, and shortly after taking the car for a motorway drive, the DPF warning light is back on.

The best way of avoiding this, is to simply avoid buying a diesel car fitted with a DPF if you only do short trips consisting of town and urban driving, modern diesel really are no longer suitable for school runs and short commutes and should only be chosen if you travel reasonable distances on motorways or dual carriageways on a fairly regular basis, but this advice is not likely to help you if you already have the car, and the persistent orange DPF warning light nagging you from the dashboard, so what else can you do?.

Fortunately, our BMW  software is a dealer level diagnostic platform, which contains the facility to check the DPF condition, clear any stored fault codes related to the DPF, and then manually trigger a forced DPF regeneration process before taking the car for a spirited (but legal!) drive down a quiet motorway.

With our BMW software package you will also be able to read out statistics on how far the vehicle has traveled since its last regeneration process, fault find DPF related aspects such as various sensor tests and back pressure exhaust readings, and also read and reset CBS (condition based servicing) parameters such as oil quality, all of which can relate to correct DPF operation and sometimes pin point a continued DPF warning light condition even after a forced DPF regeneration procedure has failed to clear the fault.

Some BMW Diesels also have a coolant temperature sensor and an EGR Thermostat, and if either or both of these sensors should fail, then they will keep the engine below the optimum temperature for DPF regeneration, and the process will never start, eventually leading to DPF filter clogging. So if you are getting ongoing problems relating to DPF faults, then these two components should also be checked for correct operation and replaced if faulty.

Replacement DPF can cost well over £1000 for replacement out of warranty and a portion of this is the diagnostic level work. Using the BMW  Software, you can run these tests and do these diagnostics  from your own driveway.


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