BMW E90 diesel: particulate filter regeneration does not start
What conditions are needed for the diesel particulate filter on an E90 to regenerate?
The coolant must be at least 75 degrees and the exhaust gas before the catalytic converter at least 240 degrees. There must be more than 10 litres of fuel in the tank. The best way is about 20 minutes of steady motorway driving at at least 60 km/h.
How can you tell regeneration is happening while driving?
The automatic gearbox's shift points rise: for example, sixth gear normally engages at 80 km/h, but during the burn only at 90 km/h. The throttle response also changes clearly.
What prevents the filter burn?
Obstacles can be glow system fault codes, an exhaust pressure sensor fault code and trips that are too short for the engine to warm up. A back-pressure fault code prevents the burn even if no filter warning shows in the instrument cluster. The burn does not start even if you try to force the conditions.
Does the burn help if the filter is already clogged?
Not necessarily. A badly clogged filter does not always recover with a burn alone, in which case professional cleaning may be needed. Do not assume that replacing the pressure sensor alone will clear the fault message.