Diesel Particulate Filters Active and Passive Regeneration

Recently, we have a few incidents regarding the DPF regen systems that have resulted in vehicles shutting down and requiring road service or having to be towed, so we wanted to go over some of the critical aspects of the regen process and what, if any, action is required by the driver and when it is necessary to call the shop.

What is the DPF? The diesel particulate filter replaces the older muffler and traps of the vehicle exhaust system. Instead of exhausting soot into the atmosphere, the DPF traps the soot, and then uses heat to oxidize it. So what exits the exhaust is much cleaner air. The soot is periodically regenerated into clean, carbon dioxide gas and water vapor. Periodically, the DPF must remove the soot that has built up along the channel walls. This is called "regeneration." It's like a self-cleaning oven. Regeneration is an oxidation process that uses heat to remove the soot from the filter.

Regeneration Process The regeneration process is actually pretty simple. There are really only two stages: Passive and Active. Passive regeneration is automatic and is continuously occurring. Active regeneration requires an intense degree of heat, a degree of heat that cannot be generated by the DPF system on its own (does not apply to 2010 and later model Volvos). To generate the level of heat required, a small amount of fuel is introduced to the system. Once an automatic active regeneration cycle has begun, it can last up to 30 minutes. During this time the vehicle must be moving. If the vehicle stops or slows down, the regeneration cycle will stop and need to be repeated.

How often does the vehicle need to regen? The number of times an active regen is necessary really depends on the operation of the vehicle. Trucks that operate in urban driving areas or make frequent stops are going to require more active regens then OTR trucks. This is normal.

What happens during an active regen?

Volvo When an active regen begins in a Volvo the Driver Information Display will read “REGEN In Progress” and the DPF indicator light will come one. If the vehicle continues to be driven during the regen process, the cycle will complete. If the vehicle is stopped or slowed, a warning lamp may come on warning of high exhaust temperature. This is normal. High Exhaust Temperature DPF Indicator

Flashing DPF Warning There may be times that the DPF Indicator will begin to flash. The flashing indicates that the filter is full and a full regen cycle must occur. There are two ways to accomplish this; continue to drive through the regen cycle or perform a parked regen. A flashing DPF indicator, by its self, is not cause for alarm. (flashing)

Check Warning There may come a time when the DPF indicator light is flashing AND a yellow “CHECK” light is on. This means you must perform an immediate regen. If you are not currently operating in an area where a full active regen cycle is possible while driving, you will have to pull over and perform a parked regen. (flashing)

Parked Regen To perform a parked regen, once you are stopped, make sure: The engine is running The parking brake is engaged Use the Driver Information Display and scroll to “AfterTreatment” Select “Request Parked Regen”.

Engine Stop If there comes a time when the DPF Indicator light is flashing and the Stop Engine light comes on, you must immediately stop in a safe location, turn off the engine and contact the shop. This is a critical event Continuing to operate the vehicle at this point may result in complete engine shut down.

A.T.S. System The most common reason the vehicle will even get to this stage is because the regeneration cycle has been disabled. While there are times when you may need to disable the regeneration cycle, you must remember to turn it back on! Ensuring that the regen system is enabled is very simple.

Enable Regeneration Look at the Driver Information Display and if there is an icon the reads “ATS” with an “X” through it, the regen cycle is disabled. To enable the regen cycle: Use the Driver Information Display to scroll to “AfterTreatment” Select “Cancel REGEN” Then select “Enable REGEN”. The “ATS” icon should disappear.

International On Internationals, the regen process is the same, but the indicator lights mean something a little different. A solid DPF indicator light means that the vehicle must continue to be driven in order for the regen cycle to complete. If it begins to flash, continue to drive the vehicle if you are on the highway. If you are not on the highway or the DPF indicator light does not stop flashing, you will have to perform a parked regen.

Parked Regen To perform a parked regen on an International, once you are stopped: Ensure the parking brake is set, the transmission is in neutral and the engine coolant temperature is at least 170° Hold the “ON/PARKD REGEN” switch in the “ON” position for 2 seconds The engine speed will automatically ramp up and the switch indicator will light up. A parked regen will take approximately 20 minutes

Engine Warning If the DPF Indicator continues to flash and the Engine Warning light comes on, you must perform a parked regen immediately. You will also here an alarm beep. (flashing)

Engine Shut Down If the DPF Indicator lamp is flashing and the Check Engine light comes on OR if the solid Engine Shut Down lamp comes on, you must immediately pull over at a safe location, turn off the engine and call the shop. Continuing to operate the vehicle at this point may result in complete engine shut down.

Parked Regen Warning Please remember, for either vehicle, parked regens should only be performed in areas that are away from people, structures and any flammable materials or vapors.