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DPF Passive Regen

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  • DPF Passive Regen

    Just testing and sharing observation, no conclusion whatsoever.
    So pls don't take this as final, just playing around with numbers and making observations.

    Made some adjustments:
    This time I omitted Forced Regen. Drove all the way down to 8% DPF, Temp was around 650C

    Name: A (Regen / 5th injector ??)
    PID: 017a
    Min: 0, Max: 1
    Fn: {B:0}
    Result: 0=ON, 1=OFF
    I discovered there is a DELAYED A=1 response aprox. 2-3sec after applying throttle/revving (could be OBD adaptor being slow reading).
    However response does not follow through continuous revs, just stops A=0, 1 sec. later.
    (maybe I did not notice this earlier, it's difficult to monitor and drive at the same time)

    Name: B (Regen Mode)
    PID: 017a
    Min: 0, Max: 1
    Fn: {B:1}
    Result: 0=ON, 1=OFF

    Previous observations below:

    Cold engine or OFF, A = 1, B = 1

    Engine starts, begins to warm up, and then 50 mins of mixed driving, mixed terrain…
    town > highway > town

    During initial warm up, nothing happens (A = 1, B = 1)
    Soot accumulates from 98% up to 100% while driving.

    But about 10mins later of driving, engine warms up, Passive regen in place
    B = 0, A = 0 and 1 intermittently.

    When value A is 0, a few seconds later, I could see soot accumulation % drops.

    Tested engine rev & speed has no impact to when A is 0 or 1.
    I was driving 70-95km/h with a mixture of high & low revs and no direct correlation at all.
    In fact I’m even seeing soot % drop when doing downhill with throttle released completely.
    But in most situations, soot % drops when A =0 ….or the % dropped a few seconds later (by that time A could be = 1) until a few seconds later A is back at 0. And the passive regen cycle continues.

    This went on until I’ve reached destination. Car was parked & stationary. Engine STILL ON, no throttle applied, transmission in Parked position.
    EGTB1S2 fluctuating range 460-490C
    Soot was at 46% and still dropping (passive regen still in place)
    A=0, B=0 constantly
    A never went to 1 (well.. it did for a millisecond or so, and then 0 all the way)
    (Passive regen still in place)
    Soot dropped to 40%
    Man I was craving for coffee.

    Waited for about 3-5 mins later, engine sound suddenly settles down (rev’s down)
    A=1, B=1 instantly
    (Passive regen stops)
    Soot accumulation = 40%

    Waited for another 5 mins… A=1, B=1
    Nothing happens
    Soot accumulation maintained at 40%

    So I did the naughty thing to start Manual Regen….. (from 40% soot)
    A=0, B=0
    Soot % did NOT fire up to 100% this time (passive regen completed)
    After a while (30sec later), engine sound settles down a little (but still higher than usual).
    DPF soot accumulation decrements 2% at a time gradually from 40%

    At 6%, manual regen stops.
    Engine sound settles down to usual.
    A=1, B=1

    1-min later soot % drops to 4% and then settles at 2%
    Still a little bit of passive regen there, or I could be dreaming, so I went for my coffee.

    So maybe we can use this to tell when a regen mode is active (B), and when DPF burn (A) is in place.
    But if you find the 1/0 confusing, you can use the ON/OFF display interface for dashboard.

    Enjoy your weekend guys. It’s been a great forum.
    Last edited by Kiat; 19-01-2018, 10:04 AM.

  • #2
    Interesting read mate👍
    Can you clarify your terminology for a passive regen and and active regen please mate.

    so do you mean the difference between car itself doing a regen and you forcing one?

    The 5th injector goes off every time any regen is being performed either forced or self activated and EGT1 temps are not affected by fuel but EGT2 cranks up after cat.


    • #3
      Spook, sorry for the typo.. I will correct it to EGTB1S2

      The active regen is just the fact that regen is activated, and passive regen doing its job.

      You can check if the 5th injector goes off when passive regen = 0.
      But as I have noticed, the soot% drops only a few seconds later after, which by that time passive could be 0 or 1.
      Fortunately, passive does not change between 1 or 0 too quickly, so you can tell if the passive was executed when the soot % drops.


      • #4
        Sorry mate I am a tad confused
        so you have active regen as being a forced regen?
        passive regen as being vehicle doing a regen based on soot accumulation reaching 100%

        not sure what you mean by passive regen doesn’t change to quickly.

        im all up for new info on this topic so it’s cool you have been looking at this

        in the automotive trade we use passive and active as two different types of regen technology depending on type of oxidation Cat and if it’s oxygen or nitrogen dioxide initiated.

        From my observation of 5th injector is-
        5th injector goes off when any regen is happening, it runs a 8ms pulse width and just changes number of injections per second depending on heat required. Only time it doesn’t inject is on deceleration just as the main injectors don’t go off. I have driven around lots with a scope connected to 5th inj / main injector/ DPF sensor.


        • #5
          100% is just a coincidence when I decided to do the test. It gives me window of opportunity to test both passive & forced regen.

          The regen active is just a indicator that a ECU regen program is 'active'. It could be Forced or Passive Regen, and the indicator will be 0.

          By 'indicator doesn't change too quickly', I mean that.... I don't think that the Passive indicator refresh-rate is showing the 8ms pulse (unfortunately). The refresh rate is not up to par with a scope read count. But it could be that while indicator is 0, there are multiple pulses in between.


          • Kiat
            Kiat commented
            Editing a comment
            Maybe there is no such "Active Regen". There's only Passive Regen and Forced/Manual Regen.
            The term 'Active' could refer to a regen taking place (i.e. 5th injector injecting to initiate burn) ?
            Anyway... back to coffee.... have a good weekend guys!

          • Spook1205
            Spook1205 commented
            Editing a comment
            The 30 sec refresh count could be the timeframe used to update DPF%.? Not sure I have not used the torque pro scangauge.
            DPF sensor voltage is heavily influenced by exhaust velocity and particle matter build up. DPF% can actually be influenced up and down depending on driving conditions. It eventually adjusts itself out.
            Exhaust velocity has a large impact on regen time frames too.
            The input into the great DPF thread has been fantastic and shows many thoughts and theories that have been tested and correlated with lots of experiences from forum members.
            My thoughts have changed dramatically along the way as I have learnt. The info you have is new to me and just trying to get my head around it.

            What is the PID you are looking at?
            Would be good to know👍 Because vehicle doesn’t have passive regen capabilities (its oxygen based regen combined with fuel / hydrocarbons to generate heat in CAT)

          • Spook1205
            Spook1205 commented
            Editing a comment
            All good Kiat enjoy that coffee mate👍

            Apologies for getting carried away as I always do with engine management stuff. It consumes my life and work🤦‍♂️

        • #6
          No, there's no 30sec update dpf% interval. The 1 & 0 reading changes intermittently. The reading could be 0 for a while and toward the end I could see soot% drop. But coincidentally at that time reading went back to 1.

          I'm not a mechanic so I wouldn't know the nitty gritty dpf stuff. I just refer to passive as when theres a Regen going on that was not triggered by a manual/forced Regen.

          sorry typos.. typing from my phone...


          • Spook1205
            Spook1205 commented
            Editing a comment
            Ah ok there would be a time frame used on DPF% correlated with voltage coming from DPF sensor and maybe engine load too.

            thinking you may of found that time frame out. Not sure what your 0 and 1 readings are then mate.

            Sometimes generic scantools don’t correlate exactly to what manufacturer has so not everything is as it seems. It’s all a bunch of binary data and a scangauge is just a program reading a OBD2 program which reads ECU data. Vehicle manufacturers often have different protocols but all need to be OBD2 compliant. This is my interpretation of how I see it, a electronic / computer engineer would have a greater understanding than me or someone who really knows programming.

            I even was a victim of this just recently when looking at manifold pressures with the scangauge2. Reading dropped 11psi from one change in the settings. Here I was thinking it’s running a really high boost because of very low compression ratio but it’s not and just relying on very high fuel rail pressure. But at least I have correct info now which is the main thing and always keen to learn.

        • #7
          The 1 and 0 are just off and on indicator. They don't show the pulse or frequency. There's probably a count interval but I don't know the interval. Anyway can't control that from generic scantools. Even a generic multimeter nowadays would be lucky if can find a true 5000 counts per sec. Bluetooth & wifi has latency issues. Scope is best solution, much less latency, maybe none or negligible.

          hey speaking of rail pressure, can you tell what's average fuel rail pressure while cruising on highway 1.6k RPM and on idle for a Fortuner? just curious. Thanks.


          • Spook1205
            Spook1205 commented
            Editing a comment
            Yeah scopes are an insane bit of gear, I love them.
            I can get rail pressure off some guys at Toyota or someone may know the PID for it.
            I can get the raw voltage out of the sensor but that won’t correlate to a fuel rail pressure until it gets to ECU. It will be something like 1v at idle up to maybe 4v.
            Knowing more exactly what fuel rail pressure is would be cool.

        • #8
          I have lots of questions, by asking I am not inferring that you are wrong just that I do not understand what you are saying.

          1. The PID 017a what is this monitoring? is Toyota using 017a with the same meaning as this from the Ram 1500 diesel forum:

          PID: 017a
          Long Name: DPF Delta Pressure EcoD
          Short Name: DPF Delta
          Minimum value: -327.68
          Maximum value: 327.67
          Scale Factor: 1x
          Unit Type: kPa
          Equation: ((signed(B)*256)+C))/100

          This says Delta pressure which I understand to mean difference before and after the DPF, yet our DPF has only one sensor?

          I will save all my other questions for later as I would like this one cleared in my head first, I have entered the pids in post 1 and have added on and off indicators on my torque pro page with EGT and % full gauges. I have returned from a drive just before and during a burn and taken pictures of the screen. I must say that unfortunately I could not make any sense whatsoever of the on/off readings which seemed to fluctuate without rhyme or reason.
          Attached Files
          Last edited by JohnLynn; 12-01-2018, 02:25 PM.


          • #9
            This is my second attempt at a post the first was rejected with the message "possible spam needs mods approval" so please mods could you delete the original.

            Could you please explain more about this? I do not understand where the PID 017a is getting it's information, the 5th injector?
            Are torque pro PIDs different between manufacturers? for instance this one from the ram 1500 diesel forum quotes:

            PID: 017a
            Long Name: DPF Delta Pressure EcoD
            Short Name: DPF Delta
            Minimum value: -327.68
            Maximum value: 327.67
            Scale Factor: 1x
            Unit Type: kPa
            Equation: ((signed(B)*256)+C))/100

            Surely Delta pressure means a pressure difference across the dpf meaning it would need 2 sensors and the Toyota has only one?

            The pictures show my screen with the information in post 1 added yet they made no sense to me whatsoever, seeming to flash on and off before and during a burn without rhyme or reason.


            • Spook1205
              Spook1205 commented
              Editing a comment
              The fact that it shows a reading of Kpa means it’s a pressure reading.
              The 5th injector is a pulse width signal which looks exactly like you see on a standard solinoid petrol injector.

          • #10
            All I can put it down to is just because it’s a program in a generic scangauge doesn’t mean it’s used by a manufacturer. Just my thoughts on it and don’t know what the PID 017a is referring too.

            Basically in a packet of information sent around the CAN it has a MID (Message Identifier) which identifies where info is coming from say e.g engine, transmission, brakes then there is a PID (parameter Identifier) which is the name and value of a reading e.g exhaust temp, yaw sensor, RPM.

            this is all sent In binary of 0 and 1’s in what’s called CAN high and the mirror image of CAN low.

            As for the one pressure sensor it has two tubes, before and after the DPF. It puts out a raw analog voltage signal from that ranges from .8v at idle on a clean DPF to up to 2v under full load on a DPF ready for a regen.
            The voltage will hold above 1v on a highway run hence why a regen can take so long. The ECU is looking for a lower voltage to complete regen but the exhaust velocity artificially holds it high.

            Its simple to to test the health of a DPF with a multimeter by just checking sensor voltage. An example is a Subaru that had idle voltage of over 1.5v and quickly peaked to over 3v on a simple snap of the throttle. Both the idle voltage and high snap throttle voltage shows a blocked DPF. It was actually cleaned out by 6 forced regens. Vehicle was only used for short trips.
            hope this helps


            • #11
              Yes this helps a lot, thank you. If the pressure sensor has two tubes then it is easy for me to understand that it is comparing pressure and outputting the result as an analogue voltage. Unfortunately I am still unclear as to what the ECU does with this voltage, how it is turned into a digital signal and of course what parameter can be used to read this information.

              I am sorry to say that I just do not understand and I hope the thread starter Kiat will explain what exactly he is monitoring here. If I sum up my understanding of all this so far hopefully someone can correct where I am wrong.

              I think of passive regeneration as vehicles getting the DPF hot enough in normal use to burn out soot, yet it seems that our engine does not do this.
              Active regeneration I think of as fuel being injected into the exhaust stream to raise the DPF temperature high enough to burn the soot. This appears to happen every 300-400 Kms or so.

              So what in this case is pid 017a measuring? is it the 5th injector firing? or something else?


              • Spook1205
                Spook1205 commented
                Editing a comment
                You are spot on with your thoughts on active / passive regen.

            • #12
              The ECU program changes the analog voltage in a 5v sensor or the frequency output in s 12v sensor into to digital data.
              An example is the manifold pressure sensor reads 1v at idle this corresponds with atmospheric pressure ( neither vacuum or boost) on full load it will get to 2.5v which the ecu knows that is full boost.
              The airmass runs a frequency of close to 2k Htz at idle but peaks about 8.7k Htz full RPM.
              so getting these values corresponds to something in the ECU program.

              If the scangauge isn’t programmed exactly to read certain data the information will be incorrect.
              its important to remember that the only true live data comes from the actual sensor everything else is perceived data.

              As for that PID don’t know. Unfortunately there are only a handful of PIDs that are completely common across manufacturers. The rest are their own PIDs specific to them.


              • #13
                Hi Spook, your numbers are very interesting, no doubt about it. but not everyone has them or know where the sensors are to start the measurements. so they opt for a ScanGauge or generic scan tool of some sort for some indicative numbers which, may or may not be so significant on day to day driving. Can you share link to the equipments /scopes & share how you use them for measurenetts and what all these numbers mean..... maybe that will encourage users to switch to using scopes instead.


                • Spook1205
                  Spook1205 commented
                  Editing a comment
                  Hi Kiat, the scangauges are a great tool and like realistically the best tool for general observation. I got a scangauge2 from recommendation from this site and I do love it.
                  I generally use Pico scopes because they have great functionality and easy to use. Sometimes I use a really cheap scope just to see what’s going on when driving around. The Pico needs a laptop. Multimeters are a great tool but capture rate is pretty slow.
                  All the equipment above is generally used for diagnostic reasons.
                  I think a simple tutorial on how to check DPF could be worthwhile for people wanting to check it. I have put more advanced stuff up for interest like injector patterns but not sure if it makes sense lol.

                  I’m pretty much stuck to a pic from phone🙄

                  I guess the only way to put a video up is with YouTube? When it comes to media and stuff it’s not something I know much about. If someone is keen to help me put some tutorials up and what is interesting I’m keen.

              • #14
                I am bobbing about in a boat on the Indian ocean writing this on a phone but I digress. My burn completed this morning, once down to 8% the temperature dropped and the indicators that I had added went to off. The % continued to fall to 6 then started to increase again as normal. So obviously this 017a pid has some connection but please could I ask once again what function is it monitoring?


                • Spook1205
                  Spook1205 commented
                  Editing a comment
                  If it turned to off once regen is complete it’s highly likely it’s monitoring that vehicle is in regen mode.