DPF (Diesel Particulate Filter) regeneration

What is a DPF (Diesel Particulate Filter) regeneration (regen) process and how to avoid costly road service call for that matter?

Basically, DPF as this acronym implies stands for Diesel Particulate Filter. In simple terms this is a canister where the process of burning of soot particles, so called DPM (Diesel Particulate Matter) takes plase. The main active components of all DPF filters are ceramic cell matter, based on Cordierite and silicon carbide ceramics. In theory the Cordierite and silicon carbide ceramics should be able to reduce DPM by approximately 70 and 90 percent respectfully. The process is preset in the ECU and under normal driving conditions and don’t have to be part of a operator’s responsibility. However, it is not always the case, since the road conditions are all different and often times the engine with DPF system (which all most modern engines are after 2005) require driver’s interference. Engine’s MCM will try it’s best to get rid of harmful soot by regenerating DPM by its own algorithm, but if it does not succeed one of four (4) scenarios will take place with DPF along with corresponding indicator lamp on a dash being lit:

1. Level 1: (Amber light with DPF sign is solid) Filter Regeneration Recommended.

DPF condition: Filter is reaching capacity.

Required action: Bring vehicle tog highway speeds to allow for an Automatic Regeneration.

2. Level 2: (Amber light with DPF sign is flashing) Filter regeneration Necessary.

DPF condition: Filter is now reaching maximum capacity.

Required action: To avoid engine derate being vehicle to highway speeds to allow for an Automatic Regeneration or perform Parked Regeneration as soon as possible.

3. Level 3: (Amber light with DPF sign and amber “check engine” light are all flashing) Parked Regeneration Required – Engine Derate.

DPF condition: Filter has reached maximum capacity.

Required Action: Vehicle must be Parked and Regeneration must be performed – engine will begin derate.

4. Level 4: (Amber light with PDF sign, amber “check engine”, red “check engine”light all flashing) Parked Regeneration Required – Engine Shut Down DPF condition: Filter has exceeded maximum capacity.

Required Action: Vehicle must be parked and a Parked Regeneration or Service Regeneration must be performed. Check engine operator’s manual for details – engine will shut down.

At Level 4 the driver can no longer get the DPF regeneration going, since the ECM will put the truck’s engine into “Derate Mode” and truck will not go any faster then 20 mph, just to allow a driver to get to repair shop. In a real life situation driver will call up for Mobile Truck Repair Service Technician to do the repair, since truck repair shops are not always an option given the fact that they normally close for the day at about 5.00 pm. Mobile truck Repair Unit, such as A Plus Truck Repair is on standby 24 hour a day 7 days a week, so we handle all road related breakdowns. Mobile truck repair technician will come and hook up his Diagnostic Equipment and initiate the process of regeneration. It is kinda lengthy process, but in most cases the whole process should not take more than an hour. The other issue that might come up is the process of Forced DPF regeneration will not start even with Diagnostic Tool hooked up to the truck’s MCM. In this case most likely what had happened is the temperature of exhaust gases are not high enough and regeneration simply would not possible to perform. If such case is present the problem for it should be looked elsewhere, meaning in other engine operation Management Systems, like fuel pressure in the rail (and I am not talking here about fuel pressure at the Doser Assembly) of regular diesel fuel supply to the injectors. Probably the fuel filter has gotten restricted and engine does not operate at full power, or there might be a fuel leak somewhere and fuel injectors get less fuel than calculated per given engine load. I guess all I am saying in here is that the broader picture at the engine systems should be taken into consideration. Technician should ask himself a question: why are the exhaust gases are not hot enough for the regen process to kick in and being carried out? And find an answer for that question. Once the underlying issue is resolved the regen process should be again called for and be carried out. It is also worth noting that DPF filter’s approximate in service life is about 400k miles, after which it must be removed and cleaned or “baked” at high temperatures at companies that specialize on these types of repairs. There are several methods for clearing out the clogged DPF out there on the market, but they are all costly and labor intense.

In conclusion, it is in the very best truck operator’s interest to monitor the condition of DPF system and not let it get extremely plugged up with soot and DPM. Paying attention to dash symbols and trying to drive long distances at a time will allow the DPF system to do its job properly and increase longevity of its potential.