Posted on 1 December 2013

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 larger engined models (330D / 530D, X3)

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. Another clue as to multiple failed DPF regeneration attempts is an increase in the oil level in the car, this is caused by failed DPF regeneration attempts, causing diesel to leak into the sump oil, diluting it and raising the oil level, sometimes to damaging levels. If you are experiencing oil level increases caused by Failed DPF regenerations, then you will need to drain the oil down to a safe level, and ideally change it as soon as possible. A Manual DPF should then be attempted at the earliest opportunity.

Failure of the car to carry out a particulate filter regeneration, 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 50% blocked, at these early stages, a regeneration attempt will generally solve the problem, however the longer it is left the greater the potential for expensive remedial work, or even a complete DPF replacement.

If you have this indicator illuminated on the Dashboard, then you need to plan a fast trip down the motorway or a dual carriageway, ideally at 3k RPM for at least 20 – 30 minutes or so, this will enable the oil, coolant and exhaust gases to reach a suitable temperature which will then cause 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 and physical condition 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, if it goes out at all.

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 cars 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 DIS 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 DIS 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, followed by its inevitable replacement, and this also applies to having a set of fully working glowplugs. So if you are getting ongoing problems relating to DPF faults, and regular DPF blockage error codes then the EGR and Coolant Termostats, and the glowplugs should all be checked for correct operation and replaced if faulty.

When testing using our Diagnostic Software, the common error codes which are created by the DPF being blocked are Error Code 480A and Error Code 481A.

Please note, that BMW DPF Systems are consumable products and will reach the end of their service life at between 80k and 120k miles (Although they can survive to higher mileages if looked after or used for mainly motorway driving). The eventual requirement to replace the DPF, is due to the amount of ash which has been collected from previous regenerations, which eventually fills to a level where the DPF can no longer continue to function correctly and the back pressure which results from a blocked DPF reaches a level where the Turbo could be damaged. If a manual regeneration does not solve the issue, then you may have no alternative but to replace the entire DPF unit, and you can save a lot of money by purchasing a Cheap Aftermarket Alternative DPF.

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 DIS Software, you can run these tests and do these diagnostics  from your own driveway.

If you are (un)fortunate enough to own a diesel car fitted with a DPF, then I would recommend using the correct low SAPS oil for your BMW, and replacing the oil every 10k miles (6k miles if oil level dilution is experienced). I also recommend avoiding cheap diesel fuel and running the car on Premium Diesel. Regular diagnostic checks should be carried out at least twice a year, to check the correct functioning of the engine and its components such as Glow Plugs, the failure of which can cause the DPF to fail to carry out normal regeneration attempts.

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