DPF operation parameters / 2019 and 2020
DPF operation parameters / Model Years 2007 to 2018

As of model year 2019, Mercedes-Benz began installing a DPF monitor in the BlueTEC Sprinter Instrument Cluster.  The DPF is the “Diesel Particulate Filter”.  It’s a symbol in the Instrument Cluster that looks like a muffler with dots in it.  It displays the percentage of soot in the DPF.  When the DPF symbol reaches 100%, the engine computer starts the automatic regeneration of the DPF.  If you read the 2019 Owner’s Manual you won’t find any explanation for the DPF monitor or how to find it in the Instrument Cluster.  In the 2020 Owner’s Manual, Mercedes put a one line explanation in the Owner’s Manual with a picture of the DPF symbol.  Since its 2007 start of production, this is the most important safety device Mercedes-Benz has ever given any BlueTEC diesel owner.  And this is  everything Mercedes tells owners about the DPF monitor.  Nothing about what the DPF does.  Nothing about random Check Engine Lights.  Nothing about how it operates.  Nothing about the incredible heat required for regeneration.  Nothing about interrupting the regeneration.  Nothing about what causes an interruption of the regeneration.  Nothing about what happens when the regeneration is interrupted.  And certainly nothing about the DPF causing the engine to suddenly stop running.  Why would they say anything about that?  Somehow Mercedes-Benz can the words to warn owners not to drink the Brake Fluid.  But for the last 13 years, words of warning about the DPF have eluded them.

Since 2007, intermittent BlueTEC Check Engine Lights (CEL) have been a “mystery”.  Dealers can never seem to verify the cause.  There have always been dozens of things that can cause intermittent CELs.  But CELs caused by the DPF have been particularly irksome.  It wasn’t until Mercedes recent diesel fraud admissions that Mercedes fully explained what events cause an interruption of a DPF regeneration.  Mercedes never fully explained the algorithm that triggers a DPF Check Engine Light.  How can your dealer solve a problem they don’t understand?  Only after Mercedes admitted to diesel fraud in Europe, did Mercedes finally fully explain the DPF regeneration parameters.  Mercedes still doesn’t explain the complex nature of the DPF regeneration to owners.  It’s easy to understand why.  Mercedes-Benz knows if BlueTEC owners actually understood how complicated a BlueTEC diesel is, sales would evaporate.  It’s not just the DPF regeneration that’s so complicated.  It’s the entire BlueTEC diesel.  Because owners don’t understand the DPF regeneration process, they don’t see the connection to all the other problems.  Let me explain one small example.  Exhaust manifolds have been around for at least 125 years.  They’ve always been exposed to extreme heat.  They aren’t complicated.  They’re just a big heavy chunk of metal.  Nothing electrical, nothing fancy.  The DPF regeneration is so hot the exhaust manifolds start rattling.  Tiny chunks of metal shake loose and are sucked into the Turbocharger where they eventually destroy the Impeller.  When have you ever heard of an exhaust manifold causing a problem?  After 125 years of experience, Mercedes had to redesign the BlueTEC exhaust manifolds.  Just think of how hot the exhaust manifolds must be getting?  Now imagine the exhaust manifolds get so hot that Mercedes had to redesign them 4 times.  This same heat is transferred throughout the engine and emission system.  Sensors, seals, plastic and every other part attached to a BlueTEC has been redesigned multiple times.  Reducing the heat required for regeneration is “job one”.  Understanding and managing the DPF monitor is one of the few active things the owner can do.  But if the owner doesn’t know what it is or how it works, they’re destined to become one more victim.

Here’s one scenario that’s nearly impossible to quantify.  Imagine it’s a normal day and you’re driving your new 2019 or 2020 BlueTEC Sprinter.  The DPF display says 100%.  This is misleading.  When the DPF monitor says 100%, it means that’s the point when automatic regeneration begins.  The DPF is not 100% full of soot.  The DPF can hold more soot.  But if the regeneration is interrupted or not completed, it enters a danger zone.  On average, the DPF regenerates every 300 to 500 miles.  City driving occurs about every 300 miles and highway driving occurs about every 500 miles.  Regeneration means the exhaust and combustion temperatures will increase to about 1400F.  This is the extreme heat required to burn off the black soot stored in the DPF.  But you didn’t notice the DPF display was 100%.  You had the Instrument Cluster in its normal display.  If you want to watch the DPF soot level, you must switch the Instrument Cluster to the DPF display.  As you’re driving you decide to stop and pick something up at a store.  You shut the engine off and inadvertently stop the DPF regeneration.  Mercedes doesn’t tell owners any of this in the Owner’s Manual or anyplace else for that matter.  If the regeneration cycle is interrupted 3 times in one cycle, the CEL switches on and the owner must take the Van to a dealer to reset the CEL.  Remember, the DPF regenerates every 300 to 500 miles.  One regeneration cycle can last 15 to 25 minutes.  If the cycle is interrupted, the cycle will resume the next time the engine starts and reaches operating temperature.  You shut the engine off and that counts as the first interruption.  Note:  If the driver occasionally shuts off the engine during a regeneration cycle it will not harm the DPF or turn on the CEL.  It’s only a problem if the regeneration is aborted 3 times in one cycle.  You don’t need to worry about one or even two interruptions in one 15 to 25 minute regeneration cycle.  If you remember to never let the “low fuel” light come on you’ll probably never have one of these episodes.  You still need to watch the DPF Monitor.  Even if you never let the “low fuel” light come on, you could give the engine a full throttle burst which will also stop the regeneration.  You could then drive for another 2 hours and shut the engine off.  However, when you restart the next day, the cycle resumes after the DPF reaches operating temperature.  You shut the engine off before the next regeneration cycle finishes and now, you’re in the danger zone with 2 interruptions.  One more interruption before that cycle completes and you’ll have a CEL.  If you’re not paying close attention to the DPF monitor, you won’t know if a CEL was caused by a part failure or your interruptions of the cycle.

You restart the engine and the automatic regeneration resumes where it left off.  However, before the cycle is finished the “Low Fuel” light goes on. This is now the second interruption of the DPF regeneration.  Note:  In over 13 years Mercedes has never told owners the “Low Fuel” warning will abort the DPF regeneration.  It’s very hard for mechanics to find where Mercedes says this in the workshop manuals.  Why not tell owners so they can avoid this accidental interruption of the regeneration cycle?  It’s easy…. don’t let the fuel level get low and you eliminate one possibility for aborting the cycle and triggering a CEL?

After the “Low Fuel” warning you stop for fuel.  You restart the engine the DPF regeneration resumes where it left off.  Traffic is heavy.  You give the engine full throttle to safely merge into the flow of traffic.  Full throttle acceleration interrupts the regeneration cycle for the third time.  Note:  Mercedes doesn’t tell owners full throttle acceleration when the DPF is regenerating will also interrupt the cycle.

Now the CEL is on.  You have no idea what caused it?  “Did something break?”  The DPF has completely stopped regenerating until the CEL is resolved.  The exhaust soot continues to build up in the DPF.  You check your Owner’s Manual to see what could have happened?  Nothing, visit your Mercedes-Benz dealer ASAP!

The Owner’s Manual doesn’t tell owners the engine can suddenly quit running when the soot level in the DPF reaches 120%.  I suppose it doesn’t matter, the DPF monitor stops at 100%. You can’t tell when it’s approaching 120%.  (Note: Some owners have personal scan tools that tell them the soot level is 200% or higher.  I’m using the 120% figure that comes from Mercedes and the genuine Mercedes-Benz DPF monitor.)

Great… it’s Sunday and you’re 500 miles from home with the CEL on.  The closest dealer is 400 miles in the opposite direction.  The odds are the engine will quit running before you reach the closest dealer.

What if you get to the dealer and there are 4 other owners waiting for service?  The next appointment is in 2 weeks.  Even if the dealer sees this is an emergency, you still have 4 other owners with emergencies ahead of you.  You look at their back lot and you see 3 more owners camping in the parking lot for their turn to get in the shop.  We’re not even going to talk about how most dealers will charge $4,000 to replace the DPF.  That’s another fight.  Why won’t Mercedes tell owners about the “Engine Off”, “Low Fuel” and the “full throttle” interruptions when the the DPF is regenerating?  If you only knew those three simple things you wouldn’t be in this mess.

There are other things that will interrupt the DPF regeneration but they are very rare and not likely.  If you drive a model year 2007 to 2018, their DPF Monitor actually works slightly better.  It will tell you when the DPF is at 120% with a flashing red warning light.  That’s actually German for; “find a place to get this thing off the road… or else!”

I’ve written out the detail instructions for Mercedes DPF monitor and can send them to you.  I hope this helps owners understand the DPF monitor and how important it is.  Mercedes published Service Bulletin LI18.00-N-054809 about fuel dilution caused by the interruptions in the DPF regeneration.  The bulletin tells dealers to explain what’s causing the DPF interruptions to their customer.  Why not put it in the Owner’s Manual?  Mercedes says the fuel dilution will cause severe engine damage.  Why wait until the owner has engine damage and then have someone at the dealer explain what caused the engine damage?  Do you really think someone is going to tell you your engine is ruined because the engine oil is full of diesel fuel?  Fuel dilution turns the engine oil into black jello.  If you’ve been using B20 biodiesel, it happens very fast.  Even if the dealer told you the fuel dilution was caused by interruptions to the DPF regeneration.  There’s no way for the driver to know when the DPF is regenerating.  Most dealers have never heard of Mercedes DPF monitor.  There’s nothing in the Owner’s Manual about the interruptions to the DPF regeneration.  How’s the customer suppose to know any of this?  If you don’t have a DPF monitor there’s no way for you to know anything about the DPF until it’s to late.

For model years 2007 to 2018, DPF Monitor kit is; p/n: 906.900.34.04.  Up to production date 1/7/2014 the DPF monitor will plug into the OBD2 connector and operate normally.  You’ll need to drill a 11/16″ hole in the L/F cup holder to mount the Monitor.  After 1/7/2014 you’ll need to run one wire to terminal #8 in the OBD2 connector for 12 volts with the key on.  I can send the documents and detailed work instructions.  As if this isn’t hard enough, Mercedes has a misprint in the wiring instructions.  I’ve corrected the misprint and attach photos of precisely how and where to install the wiring.
I’ve now had 20 to 30 owners tell me their dealer doesn’t know what this is?  They don’t know how to order it?  They don’t understand the WIS instructions for the wiring modification?  Other dealers charge $800 for the Monitor and $650 to install one wire and drill a hole.  You can get the DPF Monitor on-line from a Mercedes-Benz dealer for $600.  If you have any mechanical skills, you can install the wire and drill a hole in 30 minutes.  If your Van was built before 1/7/2014, you only need to drill a hole.  You just saved $750.