Blocked DPF Problems and Fixes

DPF Problems, Symptoms and Fixes

The Diesel Particulate Filter (DPF) is best described as the “ticking time bomb” in most modern diesels. Similar to EGR problems, the DPF can become clogged up from city driving where the car does not get up to temperature.

The whole reason the Diesel Particulate Filter came along was to clean up the diesel car image (Euro 5 Emissions, 2009). Emissions from diesel cars are a big concern worldwide and thanks to the DPF technology, diesel cars are much cleaner.

DPF’s are great for the environment and so forth, however they are a right pain when they go wrong. DPF regeneration, repairs and new replacements are seriously expensive and can lead to some vehicles becoming scrapped.

How does a DPF Work in Diesel Cars?

The Diesel Particulate Filter traps the harmful diesel gases that gets cleaned regularly by a process called DPF regeneration. The collected diesel soot particles are burnt off at high temperatures, which results in an “ash-like” after product. After the regenerating of the DPF, it can now restart the cycle of collecting harmful exhaust gases again.

There are 3 different types of DPF regeneration, which are active, passive and forced.

Active DPF Regeneration

Active reads the back pressure of the exhaust or soot load of the filter to determine when to begin the regeneration. Once initiated, the timing of the fuel injection will alter that will result in the exhaust temperature increasing to burn the soot particles.

During an active DPF regeneration, you may notice the following:

  • Higher idle RPM/Speed
  • Cooling fan working harder
  • Poor fuel economy
  • Smells from exhaust
  • Engine note change

Passive DPF Regeneration

Passive will take place once the exhaust reaches optimum temperatures where the regeneration will automatically begin. The exhaust will reach these temperatures will occur mostly on prolonged highway driving. Manufacturers that use a passive form of regeneration typically install a oxidizing catalytic converter near the engine to increase the temperature.

Forced DPF Regeneration

Forced is where the Active regeneration could not occur that has resulted in the soot levels reaching 70% and above. The diesel car will enter limp mode and will require a diagnostic tool to force the regeneration. Its important that this is done as soon as possible because once the car reaches 85% soot level, the DPF will need to be removed and cleaned.

What causes DPF failure?

Sadly DPF’s do fail and many diesel car owners do not realize how they are causing a blocked DPF. The main reason for DPF’s failing is due to car owners not doing enough miles and driving too frequently in city areas.

How long until a DPF will fail is hard to tell because some manufacturers have had to replace some in the first 3 years and some never. The most common reasons for DPF failures are:

  • Short journeys where the engine doesn’t reach optimum operating temperature
  • Clogged EGR Valve increasing diesel soot passed to the DPF
  • Faulty fuel injectors sending too much fuel to the air/fuel mixture
  • Incorrect engine oil upon servicing the car – (Low Ash + Low Sulphur required for DPF Cars)
  • Turbo failing with oil dripping into the DPF
  • High mileage car that will find regeneration harder

increase fuel in your tank when filling up

Symptoms of a Block DPF Filter

As the majority of DPF’s are installed on newer cars, you will more than likely have a trip computer. Error codes such as the DPF light or EML (Engine Management Light) will be the first symptoms of a failing DPF.

However, sometimes these warning lights can be false alarms and you should try clearing the fault using a OBD2 diagnostic tool. If the warning light continue to display, you will notice the following symptoms:

  • Loss of power
  • Reduced fuel economy
  • Poor throttle response
  • Harder or failure to start
  • Limp mode (most likely)
  • Bad smells

How to Clear a Blocked DPF and Keep it Clean

The cost of cleaning or replacing your DPF sounds scary but you can forget this following some simple driving habits. The main reason DPF’s get blocked is due to short trips and town driving. With that in mind, here are 5 ways to fix a blocked DPF:

  1. Drive Faster. If you are driving slowly everywhere in your large diesel, the DPF will become blocked. Increase your speed and plant your foot to floor to when accelerating to increase exhaust temperature and clear soot levels.
  2. Increase Your RPM. If the DPF light is on, your best bet is to drive at high RPM’s for a prolonged period until the warning lights turn off. This will increase the gases going through the DPF, thus clearing it and increasing the temperature.
  3. Avoid City Centers. If possible, you should avoid slow traffic where possible, especially if you are nearing your DPF limit or have the light currently on.
  4. Check EGR Valve. If  you have problems with your EGR valve, it will be even harder to clear the DPF. Fix the EGR issue and then try the other steps.
  5. Use High Quality Fuel. Premium fuels or diesel fuel cleaners include fuel additives that help burn off harmful particles.

If you are currently in limp mode, driving at high RPM (step 2) will be your best chance of getting out of limp mode. Once you have normal power, go for a long fast drive on high quality fuel. If the issue remains the next day, get your error codes read by a diagnostic tool.

Remove the DPF from the Exhaust System

The DPF delete is an appealing aspect if  you are having issues with your DPF. It is true, without a DPF, you will have no issues and in fact, your performance will increase with a remap or tuning of the ECU.

However, the DPF removal may be illegal is your country and it will cause more environmental damage. Although the latter will not be your biggest concern.

Have You Bought The Wrong Car?

The cost of cleaning or replacing your DPF can be expensive. For the majority of DPF’s, if you are in the region of 70 to 85% it will be eligible to be cleaned. Any higher than 85%, the DPF will need to be replaced with a new system.

Many people bought diesels as it was marketed as the “fuel for saving the planet”. However, they did not bet on having issues such as DPF failure on relatively new cars costing thousands.

It is not the Diesel Particulate Filters fault the majority of the time. Its your driving habits as the car owner and lack of knowledge with modern diesel cars.

If you are driving a few miles each day, your DPF will eventually give up and repair bills will start piling up. A gasoline engine is perfect for short journeys and equally as efficient on fuel.

Loved This Review? Share it!

What Are Your Thoughts?

  1. Hi there,
    Thanks for the rich information,
    But I would like to ask is it possible when the dpf blocked will that affect the automatic transmission shifting?
    Thanks.

  2. Hi Sharief,
    Its very unlikely that a DPF would be causing issues with your automatic transmission but you can’t rule it out. If you know that you have a blocked DPF, you could be in limp mode also. Limp mode is more likely causing the issues with the automatic gearbox changes.

  3. Hi, that made for a very good read. I’ve been asked to inspect a non starting 1.9cdti. I have little knowledge on this particular engine as I’m more of a tdci tech. So my question……

    Can a badly blocked dpf prevent the car from starting? The day before the non start it struggles to fire up and the revs was slow to build until the turbo built some pressure up. Now it won’t even fire using a wiff of easy start.
    I think it’s 1 of 2 possibilities
    1) timing has slipped so no compression although visually the belt is fine with tension
    2) a blocked dpf

    Many thanks

  4. Sounds like a blocked dpf i have the same problem with my mazda the way i managed to trouble shoot it was to duncolt the dpf secticon of exhuast from manifold side the try start the car. If car starts it is more than likely ash accumulation in dpf thats cuasing back preasure on engine preventing it from running.

  5. If DPF full light on can that cause antislip light & engine warning light to come on. This is a Toyota Fortuner

  6. are the dpf systems improved in the 2017 canyons with the 2.8 duramax or are they all the same over the years?

  7. I’ve got a 2009 1.9 Fiat Sedici with 100,000km on the clock. The engine light was on for a long time and I had less acceleration especially uphill. I guessed the problem but even after motorway driving it didn’t clear. The garage indicated a blocked DPF. They tried a forced regeneration which didn’t work so they said it needed replacing at very high cost. After a long drive 60kmph around 1750rpm the light’s gone off and the performance seems to have improved. I suspect it’s cleared itself but the garage are still telling me that I need to replace it and if I don’t the problem will reoccur. They say it has reached a point from which it cannot clear itself but this seems to be contradicted by the improved performance. Is it impossible that it’s cleared itself? Should I go ahead and replace or just wait till the light goes on again and do it then?

  8. I have Mazda 6 Diesel 2010. It has done 125k miles. It gives no trouble to start in the morning BUT after I have driven it for 30-40 minutes (on a motorway) and if I stop somewhere it will not restart for 10-15 minutes. However if I sit patiently for 10-15 minutes it starts again. Is it DPF problem, nothing showing on the dashboard.

  9. Hi
    My dpf light came on so I regend the car, the light turned off,
    The light has now come bak on, so took it to the garage plugged it into the computer showed up no faults, regend the car, once finished the went to reset the light and it won’t go off, w
    But could tell me what to do next.
    Thanks kerry

  10. Hi – useful article. My 2014 Mitsubishi ASX begins missing felt through the steering wheel and pedals only when motorway driving. Could this be a DPF issue? As only just had full service
    Thanks lisa

  11. Hi Lisa – I wouldn’t say this is to do with a DPF Failure. Unless there is a large amount of black smoke coming from the exhaust, it could be a regen but I highly doubt it. I would report back to the person who serviced your car.

  12. I have been using the expensive diesel for a while now in my 2015 1.6 CR-V and have been thinking about going back to ordinary diesel but after reading this I will be sticking with the expensive stuff.

  13. Hello just had to have a forced regeneration on my mazda 6..
    Could someone please tell is it worth doing a forced regeneration say every six months before the fillter has time to block and before the dpf light comes on with a machine I have brought myself just like the one they use at the garage. .
    The machine apparently will do a forced regeneration if required. .
    Many thanks in advance..

  14. I just bought a used Nissan Vanette van and not being farmilia with DPF warning sign I continued to drve without regeneration. Now the check engine sign has come on. I suceeded in doing manual regenaration but both signs have not gone out. What does this mean?

  15. Hi I have a bit of an issue . My Audi a6 4g engine had a dpf that got blocked as it had not regenerated in some time . I also have a p0104 code related to the air flow sensor which I replaced with a genuine new part . Got the dpf fully cleaned and also inspected . Checked egr with vcds system and all is good . Also replaced the pressure sensor . However the car will not force regen and the p0104 fault never goes away . Car is not in limp mode . All seems good but is not . Any thoughts as to why this is happening and to why it will not regenerated. Audi cannot find the problem after 3 weeks in the garage .

  16. Hi
    I have a Jeep Grand Cherokee 2011. I have issues with dpf filter but am reluctant to replace as I hear so many still don’t solve problem.
    I wonder if using cruise control can be a factor in dpf problems as I have been a great user of this.
    Mechanic cannot locate any other problems..car well serviced.

    Thoughts?

  17. Hi I’m just wondering does the light always come on when the DPF is blocked all the symptoms match what’s happening with my Nissan qashqai 09 but no light is coming on and have had it plugged in and nothing is coming up

  18. Just Had my DPF Filter Cleaned,drove away and the ” Engine Requires Service” light has come on for about 20 seconds then goes out,Why?

  19. Hi Jim,

    I would advise that you take it out for a spin whilst keeping the revs up higher than usual. If after a long drive it is still comming up, go back to the garage and ask them to plug it in to a diagnostic. Sometimes you will need to remove the code that is stored on the system.

  20. Hi, i have a Citroen c4 grand Picasso 2007, semi-automatic 6 gear with paddle shift, 2 weeks ago i have a warning on my dashboard saying : ” Particle filter might be blocked “, i went to service and they checked it and they said is ok, doesn’t need regeneration or changed, i changes my filters, oil, fluid additive and yes i drive my car in city most of the time below 40 mph, i did some research and this might be the cause, sometime when i go high revs the warning still comes on and goes off after a couple of sec or 1 min, i have no other warning, every button from the car works, every light. Also when i accelerate sometime i feel a bit loss of power and the car is like going forward and backwards if i dont give more gas, the car is a bit old but have no problems beside thid, also when i drive it when going from 1st gear to 2 gear i hear sometime when it’s shifting, no warnings no nothing, spoken with some services and they said as long as i dont have a failure or a warning its common on Citroen, i would like more opinions please, thank you!

  21. I just replace the particulate filter and sensors as Chevy said that was the problem. Guess what it’s still saying the filter is clogged and the computer is still putting the engine in low power mode. 2011 Silverado. Any ideas?

  22. Hi,i would like to know what is the step to remap the E.C.U for dpf fault!
    The engine model is a : KDY121 toyota
    Thanks in adavance for your reply

  23. My Qashqai 1.5 DCI just had a new dpf a new turbo and egr valve replaced. Warranty will pay for the turbo and the valve but won’t pay for the dpf.
    The is second hand with 43000 miles and I bought 6 months. I have a bill for £1850 for labour and dpf. Be careful if you buy a diesel car. Don’t trust warranty.
    I am sorry just having a moment.

  24. Hi, I have got a seat on finance 11month ago. Within the first 6 weeks the Dpf filter light came on, this continued for a few weeks. I took it to the garage who said the Dpf light was faulty and not a problem with the actual filter it’s self. Last week my car broke down, the garage said he oil has leaked out everywhere and the tubro needs replacing along with the dpf filter. The car is now out of warrenty, however I am indisbutes with the garage as I believe the fault was there when I brought it to the garage after 6 weeks of purchasing the car.

    Can a problem with the Dpf filter cause the blockage, for oil to spill out and need a new turbo? Or is it likely to be something different?

    Thanks.

  25. Hi I have a Citroen grand picasso 2011 I had an error message showing the service light and saying that particle filter additive too low repair needed I did ropes up the additive but stillvits showing the message. How can I remove it.

  26. I have 2008 Toyota coaster…it does Not finish Re gen ..even doing with mechanic computer..it fails….and Engine light comes on..alredy cleaned DPF..change sensors n EGR also replace brake exhurst valve
    …it seems DPF doesn’t go that hot ..to Regen

  27. Hello
    I have a 2011 grand cherokee on finance. I had an inspection done on the vehicle after i had some problems with it and they found what they believed to be a problem with the DPF.
    We had a forced regen done which resulted in the car driving perfectly for 1 week and then went back into limp mode with the same code coming up.
    Finance company have agreed to replace the DPF…. is there any other part that could be a factor? Or that I would need to replace at the same time to increase chance of permanent fix?
    The car doesn’t start any more (sounds like it’s choking) and I am afraid if they fix the DPF it could have something else wrong as a result.
    Any advice would be greatly appreciated

  28. Hi, so if i have brought a car, the EML came on within 12 hiurs as they had obviously just turned the EML light off, the fault it is coming up with is the dpf filter blockage.
    The garage said they have put some adictives to help clear the engine and filter out and to go for a driver keeping the car over 2k revs, which i have done, i went on a 50mile trip up a duel carrigeway with no traffic keeping at 50 in forth gear to keep the revs a bit higher than usual but the EML light has stayed on even after the drive which i was told should clean it out,
    What do i do from here? Take it back and tell them the filter needs to be replaced and get into a debate with them or ask for the money back and stay clear of the car?

  29. Hi friends
    I have Toyota coaster 2008.When I do DPF Regen,it fails n engine light cimes on i have clean DPF 3 times also mechanic change EGR ,Exhaust brake,change all injectors n sensors. it cost me damp 9k already…
    Do u guys thing I did change DPF

  30. Hello
    Replaced blocked DPF filter on 07 Navara reset error codes car went well for the 1st day but then light come back on and went back into limp mode. Could this be the sensors ont the DPF or something else.
    Regards
    Troy

  31. Hi I’ve had my ford smax zetec 2lt diesel for 10 day on finance it was back at the garage after 3 days they said they’ve changed the filter and sensors and he said he’s bin driving it all weekend no problems great so I thought so it drove back great last night no problems I get up this morning at 6 take my husband to work and on the way home I get engine malfunction and I lose all power I know nothing about cars but I know this shouldn’t be happening I’ve only got 2 more weeks of warranty left so I need some advise of what to tell the garage when I take it back I’ve got myself into debt for a car that doesn’t work properly the last time he plugged his computer in he said it was a boost issue I’m thinking it’s the turbo and they’re hoping it runs out of warrenty before they have to pay for a new one to be honest

  32. Hey friends ,
    I own a Isuzu elf truck and the dpf light ie limp mode came across, cleared it but afterwards it was back . The car had its ‘maflas’ the catalyst removed some years back..Would i clean it even still without the ‘maflas?

Leave a Reply

Your email address will not be published. Required fields are marked *