Diesel Tech Q&A: Ford DPF Cleaning

Ford pickup truck towing a Raptor trailer
Ford 6.7-liter Power Strokes, like all modern diesel pickup engines, are designed to automatically go into an “active regeneration” cycle to clean the diesel particulate filter (DPF) when it reaches a certain percentage of soot buildup or the truck has reached 100 to 500 miles since the last cleaning cycle or “regen.” If the DPF regen cycle is not completed or properly done, it leaves the filter plugged up, and the engine will go into a Limp Home mode where power is lost and additional measures are needed to clean the DPF. Photo: Bruce W. Smith

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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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.

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  1. It’s a shame that you can’t do an operator manual regen so as to get out ahead of this problem without having to wait for a 100% clogged situation.

  2. Frustrated with local Ford dealers here in the Sacramento area. At 95,000 miles our 2015 F-350 said something like “DPF filter at max service now.” After getting a quote for $3,500 at the dealer, we had a diesel emission specialist remove and clean, and they said it wasn’t that bad. The Check Engine light was on again, and we were told the computer needed to be reset. Did that today at the dealer. The dealer is saying the filter needs to be replaced anyway. Who to believe?

  3. Can you be towing your fifth-wheel when the active regen process is taking place, or do you have to unhook the trailer every 100 to 500 miles when the sensors decide cleaning needs to be done? I intend to do a lot of long-distance driving and want to know if I’ll lose all the power to tow during this regen. Thanks for answers.

    • Bruce W. Smith replies: Yes, there’s no reason to drop the trailer when the dash indicates an active regen is taking place. In fact, towing is probably better for those regens because the engine is producing more heat than it would running solo, so the burn-off of soot (carbon) in the diesel particulate filter (DPF) wouldn’t take the normal 20 to 40 minutes that it would under unladen driving conditions.

      The active regen is handed different ways by the diesel manufacturers. The engine control module (ECM) on the Cummins 6.7-liter, for example, uses a “post-injection” technique that injects an extra amount of fuel into the combustion chamber, occurring late in the power stroke and/or through the exhaust stroke. That raw fuel goes into the diesel oxidation catalyst (DOC), where it ignites. Ford follows a similar regen system in the Power Strokes. GM uses a hydrocarbon injector (HCI), aka the “9th Injector,” to inject the fuel directly into the DOC just before the gases exit it. Those extremely hot exhaust gases immediately go into the DPF.

      All three systems end up having the same end result: getting a blowtorch-like fire coming out of the DOC as it enters the DPF so the carbon/soot residue inside the DPF is reburned and turned to ash. When the diesel’s ECM sees that the pressure variance measured at the front and rear of the DPF are once again within factory parameters, indicating back pressure is within spec, the regen shuts off.

      In most situations an active regen takes anywhere from 20 to 40 minutes driving at 50 mph-plus, to complete. If the engine is shut down prior to complete regen, the DPF will still be partially plugged, and the system will soon command the regen to begin all over. Fuel economy drops noticeably when in active regen because there’s a lot more fuel being pushed through the injection system than would be used in “normal” driving conditions.

      GM technicians say the LML’s active regen process initiates once 42 grams of soot have collected in the DPF or after 700 miles without active regen, whichever comes first. We’ve heard the LP5 Duramax has an even more aggressive active regen cycle but don’t know for sure.

      By the way, diesel exhaust fluid (DEF) is not used for regens, just diesel fuel. DEF is being continuously injected whenever the engine is running, as dictated by the ECM. DEF is used in the chemical process to convert NOx to harmless water vapor.

  4. I wish diesel owners would get into the preventative mode. The DPF is a filter — it needs to be changed or cleaned before the bells and whistles go off. Three years on a regular driver is long enough. Get the filter cleaned before the computer forces you to a dealer with the software to reprogram the computer. Many times regeneration is thought of as the diesel particulate matter [the black stuff] “going away.” Regeneration (in reality) is compacting the matter into the filter and making room for more soot. It has to be cleaned out or replaced. The computer issues (reprogramming) should be a free service under a recall status (emissions) IMHO. Be preventative.

  5. We have a 2008 Ford F-350 6.4-liter truck that our local dealer has been fighting with a problem on for the past two years to no avail. We pull a nearly 43-foot Dutchmen Voltage 3800 toy hauler. The truck pulls fine on flat roads, but the minute we hit an incline, it goes into Limp Home Mode (LMH). The service technicians have had the cab off three times, changed the fuel pump three times, fuel rails once, throttle cable once and all the filters twice. Just before going into LMH, the Clean Filter light comes on. The light eventually goes out after several miles of driving. If I pull over and shut the motor off and restart it, it runs fine until the next hill. It took us five hours to drive from Lake Havasu City, Arizona, to Flagstaff, which is typically a three-hour drive. The dealership has given up on fixing the truck and won’t touch it anymore. I spoke with a mechanic who works on motorhome diesels, and he told me to remove all the EGR (Exhaust Gas Recirculation) equipment and put on a 4-inch exhaust with a chip. He said if I do that I will never have this problem again and will gain horsepower and torque.


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