BMW Diesel Particulate Filter Information

diesel particulate filter (DPF) is a device designed to remove particles / soot from the exhaust gas of a diesel engine. Soot remains in the DPF for a short period of time before it is regenerated, either passively at low temperatures; or, actively at higher temperatures. 

After the regeneration process where soot is oxidized, the remaining non-combustible material is called ash. Most of the ash collected in the DPF originates from the engine oil; and, to a lesser extent, diesel fuel. 

Ash is, therefore, formed in the DPF over long periods of time, following repeated regeneration events and builds up in the DPF until it is removed through filter cleaning.  The specific ash properties, and the ease with which the ash may be removed from the DPF are strongly affected by a large number of factors occurring over the entire operating history of the filter.  

Soot and Ash Differences | Apex Automotive

Figure 2: Soot and ash removed from a Diesel Particulate Filter (DPF).

Although the ash only makes up a very small fraction of the incoming soot, it remains in the DPF indefinitely and builds up to high levels.  In fact, after only 33,000 miles, the amount of ash in the DPF may equal the amount of soot (prior to regeneration), and after 150,000 miles, nearly 80% of the material trapped in the DPF is ash.  In other words, a high mileage DPF contains much more ash 

DPF filters go through a regeneration process which removes this soot and lowers the filter pressure. Diesel particulate matter burns when temperatures above 600 degrees Celsius/ 1100 degrees Fahrenheit are reached.

The following codes are commonly found in ECU memory when the diesel particulate filter needs to be cleaned or replaced; or, if impact damage has crushed a part of the exhaust pipe causing exhaust gas restriction. 

452A - Calculate Ash Load is more than 100 Grams





4530 - Charge Air Pressure Control Small Turbo Control Deviation

Diesel Regeneration, whether forced or controlled automatically by the ECU, will not occur if codes 480A or 481A are present in the ECU.


BMW Diesel Particulate Filter Regeneration (prerequisites)

DPF Regeneration, controlled by the ECU, should occur automatically when:

  • manufacturer code 480A is not present in memory
  • manufacturer code 481A is not present in memory
  • codes are absent, and conditions are met.

I have cleared codes and forced regeneration using SnaponAutel, Launch, Autologic, and BMW OEM scanners. 


According to our tests and experience with BMW diesel vehicles, the optimum engine rpm for DPF regeneration is between 1800 rpm and 2000 rpm.

  • Engine RPM's lower than 1800 RPM may not produce sufficient exhaust gas temperatures at the Diesel Particulate Filter
  • Engine RPM's higher than 2000 RPM are may actually increase gas flow enough to cool the Diesel Particulate Filter


Snapon scanners fail to show data relative to the last regeneration. The other mentioned scanners show mileage and time date signifying last successful regen.

Diesel Particulate Filter Regeneration prerequisites include 10L of fuel, engine operation temperature, and it is recommended by the manufacturer to maintain steady state RPM's for 20 - 30 minutes.

Cleaning methods include

Labor requirements 

BMW Diesel Engines

BMW 3-Series (E90/E91)

  • 2.0L Diesel (N52B25A)
  • 3.0L Diesel (306D3) (306D5) 

BME 5-Series (E60/E61)

2.0L Diesel (N52B25A)

3.0 Diesel (N57D30A) 



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