News & True RV Stories

Cummins DPF Instructions

Published October 06, 2008

Category: Tech

10-5-08 Sunday morning at 7:30am I received a call for help from a couple in South Carolina. They recently purchased a new 2008-45' Magna Donatello with a Cummins ISX 600HP engine. Bill & Carol were leaving there property up in the hills of South Carolina, on the way down is a long descend of twists and turns, they safely idle down at minimal speeds around 10 to 15 mph. Early in there descend the "DPF" (Diesel Particulate Filter) illuminates. Shortly thereafter the "Check Engine Light" illuminates. They keep going and as they near the bottom of the hill the "DPF" lights starts to flash. When they get to the bottom the "Stop Engine" light appears so Bill pulls off into a service station. Four tow trucks and 27 hours later Bill and Carol get towed into a Cummins garage some 90 miles away, the tow bill is $1,670.00. At Cummins they find his DPF is extremely plugged and needs to be replaced, its junk. A new diesel particulate filter is $2,000.00 or more not including labor, it is probably a couple of days out as its not in stock. Now I am going to share with you how to avoid this from happening.

The above is a true story and it could realistically happen to anyone with similar circumstances. If you have the new ultra low sulfur diesel (ULSD) Cummins engine please read this close. On your dash you have a 3 position switch labeled "Regen". Regen stands for regeneration. This switch should always be in the center position which we call "Auto". Down is "off", center is "auto", and forward is "forced Regen". In the auto position the engine will perform a Regen and clean out the DPF as needed, however this can only be done at speeds over 25 mph. A typical Regen takes 40 minutes and during this time it cleans out the DPF. During the Regen you will observe a "Hot Exhaust" lamp come on your dash, this is normal and telling you that 900 degree heat is currently coming out of your exhaust pipe. When it’s done the "Hot Exhaust" light will turn off. There is no reason to ever have it turned off. Above in Bill and Carol's situation when the DPF light illuminated they should have stopped on the side of the road safely and turned the Regen switch "on" to perform a forced Regen. This would have taken 40 minutes but saved him 26 hours and somewhere around a $5,000.00 bill for towing, DPF, and labor.

When the DPF Lamp illuminates, the after treatment Diesel Particulate Filter needs to regenerate within the next 2-6 hours of operation. This is accomplished by:

1) Changing to a more challenging duty cycle, such as highway driving, for at least 20 minutes


2) Performing a “Parked” or “Forced” regeneration. When the DPF light flashes, the above action should be taken in 1-2 hours.

A flashing DPF light combined with an illuminated Warning or Check engine lamp indicates that the DPF needs immediate regeneration. Engine power will be reduced automatically and a Parked forced regeneration is required.

If a parked regeneration is not performed the red “Stop Engine” lamp will illuminate, at this point the damage is done and you need to be towed into a Cummins garage for service.

To brush up on my Cummins DPF info I sought out Rick Garlitz of Cummins Northwest. Cummins Northwest is located 1 mile north of Guaranty RV’s I-5 location; it was a long drive... Cummins Northwest supplies engines to Country Coach, Monaco, and many other vendors in the region. We walked and talked during a mini-tour of the facility. I took a few photos of all the engines in stock and Rick also gave me some informative Cummins DPF/Regen instructions to hand out. Please send me an e-mail with a mailing address and I will send you one.