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Diesel Tech Q&A: Ford DPF Cleaning

Originally Published in Trailer Life Magazine

JUNE 2019
Ford DPF Cleaning

Red letter Q

Silver Ford F-250 truckhave a 2106 Ford F-250 6.7-liter diesel that we tow a Heartland Big Country fifth-wheel with. On three occasions, only when towing, we suddenly start to lose power and get a warning light saying Drive to Clean. We have to unhook from the trailer and usually drive at highway speeds for 20 to 30 minutes to clear the warnings on the instrument panel. We can then hook back up to the trailer, and everything is fine. The pickup has 76,000 miles, with probably 15,000 of those towing. Any help would be appreciated.
Jerry Newton, Canyon Lake, Texas

Green letter A

The three times your F-250 experienced power loss are indicative of the engine going into Limp Home mode because the diesel particulate filter (DPF) was plugged up and the engine was protecting itself from damage. The Exhaust Overloaded, Drive to Clean warning (or Exhaust at Limit, Drive to Clean Now) popping up on the instrument-cluster display is a serious maintenance message related to the state of the DPF. What that warning means is the DPF has reached being 100 percent plugged, as monitored by sensors mounted in the DPF that measure exhaust pressure differential (delta pressure) and/or the truck has exceeded the maximum number of miles since the last completion of an active-regen cycle, which can be anywhere from 100 to 500 miles, depending on how the truck has been used.

The normal message related to DPF cleaning and maintenance is Cleaning Exhaust Filter, which means the computer has initiated what is called an active regen by feeding raw fuel into the cylinder late in the exhaust stroke so that raw fuel ignites as it’s going into the DPF.  That exhaust gas temperature (EGT) feeding into the DPF gets to between 950 and 1,050 degrees, which is enough to reignite the soot accumulated in the filter. If you are driving the truck in the proper manner (above 30 mph, preferably from 55 to 65 mph) and for the proper amount of time (15 to 30 minutes) during this active regen/reburn, the DPF will be cleaned, the message will disappear, and the instant MPG indicator will jump up because less fuel is being used.

However, if you don’t drive the truck for a long enough time for this regen cycle to finish, the DPF will not be cleaned and/or the engine computer will not reset the miles driven between regens. The engine computer and/or sensors in the DPF see that as a big problem, and that’s when the Exhaust Overloaded, Drive to Clean warning comes on. If the driver ignores this and doesn’t drive the vehicle so the regen can complete, the computer will put the engine into Limp Home mode, which, as you experienced, significantly reduces engine power.

Sensors in the engine compartment of an F-250 truck

The Ford Super Duty exhaust system’s diesel particulate filter (DPF) has numerous sensors plugged in to monitor exhaust flow, nitrogen oxides (NOx) and exhaust gas temperature (EGT). The engine computer uses that information to control the regeneration cycles to keep the DPF from plugging up with soot, which is basically diesel that hasn’t burned completely. Photo: Bruce W. Smith

Operator Commanded Regeneration

When that happens, you need to manually command the regen to begin, as noted on page 32 of the 2016 6.7-liter Super Duty Diesel Supplement. This procedure is called Operator Commanded Regeneration. Ford says this can be done only when the DPF load percentage has reached 100 percent, the Exhaust Overloaded, Drive to Clean message appears in the information display, and the driver is not able to drive in a manner that allows effective automatic cleaning (active regeneration), or the driver instead wishes to manually start regeneration (cleaning) of the DPF. Then the truck must be in Park.

The instructions to get Operator Commanded Regeneration are as follows: Start with your vehicle engine fully warmed and then press the Info button on the steering wheel until the information display reads one of the following choices: EXHST XX% FULL CLEAN? Y/N or EXHAUST FULL CLEAN? Y/N. Answer Yes to either prompt, and then follow the prompts regarding exhaust position as needed to initiate Operator Commanded Regeneration. The display will confirm when the operation has started and finished.

If the DPF is near or at saturation, a message requesting permission to initiate filter cleaning will display EXH AT LIMIT CLEAN? Y/N. Answer Yes to this prompt, and then follow the prompts regarding exhaust position. Ford also says that if you need to cancel the Operator Commanded Regeneration, pressing the brake, accelerator or shutting off the vehicle will stop the procedure.

The issue could also be a bad sensor monitoring the DPF or a related part of the exhaust system. If this were my truck, I’d have a reputable Ford dealer scan it for codes and make sure it is flashed with the latest software updates, including those related to the DPF/regen system.

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To ask Bruce W. Smith a question about maintenance, repairs or upgrades to your diesel truck, SUV or van, go to the Diesel Tech Q&A home page, scroll down to the Leave a Reply box and type in your question. Please include your full name and hometown.

Bruce W. SmithA respected automotive and RV journalist and longtime Trailer Life contributor, Bruce W. Smith has held numerous editorial titles at automotive and boating magazines, and authored more than 1,000 articles, from tech to trailering. He considers his home state of Oregon a paradise for RVing and outdoor adventure.

Read More: Diesel Tech Q&A

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