DPF related error

This is the Forum for all your Citroen Technical Questions, Problems or Advice.

Moderator: RichardW

Rob_E
Posts: 7
Joined: 20 Aug 2021, 19:29

DPF related error

Post by Rob_E »

Hi,
The engine management light has recently come on on my C4 (2005 2.0 HDI hatchback, currently at 188'000 miles), with the usual rather generic message on the display " depollution system faulty".
I've plugged it into Lexia and there were several permanent faults shown.

The first which has been there for a bit longer and seemed to be able to be present without the engine management light being on was:
"Additive system Fuel filler cap signal fault"

I have now fitted a new Fuel cap sensor and this fault has now gone, and the ecu seems to report correctly on Lexia when the fuel cap is present or absent.
As I said this fault is now fixed, but I mention it in case it may have a bearing on the other more persistent fault.

The second and more recent, and more persistent, fault is:
P1445: Additive system Maximum additive level in the particle filter reached.

What does this fault mean? Is it a consequence of the previous fault, and saying that it has been constantly adding additive to the fuel and now there is too much in the filter? This is what the local garage thinks.
Or am I right in thinking the DPF is a service item on these cars and you are expected to replace it with a new or recon one at some point; so is this message saying this is now due because over it's lifetime it has reached the limit of how much additive it can handle?
User avatar
GiveMeABreak
Forum Admin Team
Posts: 26065
Joined: 15 Sep 2015, 19:38
x 2992

Re: DPF related error

Post by GiveMeABreak »

This fault means the amximum amount of additive has been dumped into the particle filter and you DPF is due for replacement or cleaning. A DPF is a service item. There are components like engine oil and debris, Cerine from the additive itself and ash that cannot be burnt off by the filter and it is these items that clog the filter up.

Your vehicle is estimating that your filter is getting near capacity or has at least reached the level were it needs cleaning or replacing.
User avatar
mickthemaverick
Donor 2021
Posts: 7386
Joined: 11 May 2019, 17:56
x 2095

Re: DPF related error

Post by mickthemaverick »

Hi Rob,
I had a similar issue with one of my maintenance fleet and cleaning the dpf resolved the issue completely and it still has not returned!! Details in this thread:
viewtopic.php?p=672106#p672106

If you are going to try that, read through all the thread to pick up all the tips from various members. Good luck! :)
Rob_E
Posts: 7
Joined: 20 Aug 2021, 19:29

Re: DPF related error

Post by Rob_E »

Thanks for the quick response.
So it sounds like this is a coincidence then that these faults came up in succession, and the fuel cap issue had no bearing on this one.

The local garage were talking about forced regeneration, but I assume there would be no point in that, as the normal regeneration appears to happening and it isn't reporting that the filter is blocked; and that if the issue is clogging by things that can't be burned off forced regen would be of no more benefit than the normal regen cycles?

I did delete the fault code, but it came back immediately without me even starting the engine; is this because it is triggered by a counter for the amount of additive used rather than any actual measurement of DPF state?
In Lexia I have seen there a number of DPF related state:

"soot load" which goes up to 100% then drops back to 0 after regen.
"Degree of particle filter soot clogging" (the ash content?) which has now reached 104%
"Particle filter load state" which reports "filter in correct state"

If it is just an estimate does that mean that potentially I don't really need to do it yet?

I did a test drive with Lexia running and recording stats, at a point when it was about to do regeneration as the soot load was approaching 100%, I will try and show it here.
Image

Is the differential pressure a good measure of if it is really getting clogged? I saw one document that seemed to be saying 800mbar was the point the ECU would raise a fault for it being blocked. it looks like mine did not get about 250mbar at any point, and did go down after the regen.

I realised after recording it that maybe exhaust flow would have been a more useful parameter to have recorded too.
Rob_E
Posts: 7
Joined: 20 Aug 2021, 19:29

Re: DPF related error

Post by Rob_E »

mickthemaverick wrote:
23 Aug 2021, 13:33
Hi Rob,
I had a similar issue with one of my maintenance fleet and cleaning the dpf resolved the issue completely and it still has not returned!! Details in this thread:
viewtopic.php?p=672106#p672106

If you are going to try that, read through all the thread to pick up all the tips from various members. Good luck! :)
I spent too long writing my reply, that I didn't see your in between. Thanks, I'll take a look at that thread.
User avatar
GiveMeABreak
Forum Admin Team
Posts: 26065
Joined: 15 Sep 2015, 19:38
x 2992

Re: DPF related error

Post by GiveMeABreak »

Forced regeneration is not advised unless absolutely necessary due tot he toll it takes on components without the air ram of the car travelling to aid in cooling them. And, yes, it will serve no purpose in this case as it is currently regenerating - but as I said, those elements I listed cannot be burned off and it is these that leads to the need for eventual filter replacement / deep cleaning.

Second, the additive level is estimated only - not physically measured, so the engine ECU will flag up the warning as the maximum amount of additive in grammes has been dumped into the filter (which is essentially the amount of Cerine which has been deposited). At 188k miles you have well exceeded the life of the filter and this warning will remain in place until you replace it and tell the Engine ECU you have replaced it.
Rob_E
Posts: 7
Joined: 20 Aug 2021, 19:29

Re: DPF related error

Post by Rob_E »

Some interesting videos on that other thread, I think I have seen some others from the same guy before, he seems to have a lot of similar videos on DPF cleaning.

I'd be tempted to try it if I was more confident at being able to remove and refit it. On the 1.6 I think they are fitted on the front of the engine so perhaps easier to get to, or maybe it's just the grass is always greener and the radiator makes it equally difficult.
But on the 2.0l it's the other way round and the exhaust comes out the back of the engine, so I'm a bit apprehensive of how much access there would be to the front connection of the DPF to get it off. There is no access from the top, and underneath I think there is only very limited space between the body and the subframe as the connection is tucked up behind the engine. I believe the DPF does actually split apart on this one, unlike some of ones in that guys videos, which if I understand correctly is the catalyst in the front portion and the actual DPF in the back, with four bolds holding it together. But I think it has to be removed from the car to be able to access those bolds.
Has anyone removed one on a 2.0l engine? Is it actually not as difficult as I'm imagining? [-o<

On the other thread there was also mention of Halfords DPF Deep clean, is that likely to be suitable in my case? looking at their website they seem to talk more about soot, and it sounds like they add something to the filter with it on the car. Would such a process be able to remove the ash? Seeing the amount of stuff coming out on those videos makes me think without it being physically removed from the car to flush it out, it wouldn't be able to clean it properly?

It's all bad timing as I have my MOT coming up shortly. I'd heard somewhere that having the engine light on was an instant failure, but I think it was on one of the posts on here somewhere I read that that only applied to cars after 2008, but the post was from a couple of years ago, so not sure if it's still the case? If so then at least I could perhaps check it passes without any other issues before spending out on this one.
User avatar
GiveMeABreak
Forum Admin Team
Posts: 26065
Joined: 15 Sep 2015, 19:38
x 2992

Re: DPF related error

Post by GiveMeABreak »

Not all 1.6 HDis have the catalyst at the front - my new 1.5 Aircross does - so makes it easier to access - however, the exhaust is still emitted at the back regardless of where these are fitted.

There's the pre-catlyst and then the catalytic converter and then the DPF.
If you opt to have the DPF cleaned, then it depends on whether it is a deep clean or regular clean. A light clean involved squirting chemicals into the DPF to loosen and try and dissolve the ash. More blocked systems usually have to come off for a proper clean.

There is always the risk of damaging the actual particle filter part of the assembly as these are quite delicate.
Rob_E
Posts: 7
Joined: 20 Aug 2021, 19:29

Re: DPF related error

Post by Rob_E »

So it's been a while since I posted this. But in the end I went for the hybrid DIY approach and got a mechanic to remove the DPF from the car for me to clean this weekend, and is coming back tomorrow to refit it once I've finished the cleaning.
As expected there wasn't very much soot in it, as it had regenerated only about 50km prior to being removed, but there was a lot of red ash that came out of it.

I did largely the technique shown in one of the videos on the other thread, using caustic soda, then diluted brick acid (hydrochloric), then lots of rinsing and back flushing.

This evening I plugged Lexia in to tell the ECU that the particle filter had been replaced ready for the refitting; this seemed to work quite painlessly I use the particle filter replacement option on the additive ECU and the counter has been reset to zero, this is also reflected in the injection ECU display of the counter too.
One thing that puzzles me slightly is that I would have expected the soot and ash levels displayed to also be reset to zero as it had been told it has a new/cleaned DPF. But they have gone down, but not to zero.
Before the reset:
Image
Image

Then after the reset:
Image
Image

So it thinks there is a soot load of 7.84% and ash clogging of 27%. Anyone got any idea why it didn't go all the way to zero?
If I had driven it I might have assumed it had some how measured that it wasn't completely as clean as a brand new one, which I'm sure is the case as the cleaning almost certainly didn't get everything out. But when I did the reset the DPF isn't actually physically installed in the car yet.
Did I do something wrong, does the reset need to be done after the car has been started at least once post the cleaning/replacement? The additive counter has reset and the fault code is no longer registered, but I was just curious where these numbers came from, as I expected them to be zero.

Rob
User avatar
GiveMeABreak
Forum Admin Team
Posts: 26065
Joined: 15 Sep 2015, 19:38
x 2992

Re: DPF related error

Post by GiveMeABreak »

You have to bear in mind these values are theoretically calculated - not actual...I'd also make sure you do fully top up the additive too while you are at it - as you have notified the engine ECU that you have done this. This will affect the warnings and calculations going forward and it is now expecting that the additive has been topped up.
Rob_E
Posts: 7
Joined: 20 Aug 2021, 19:29

Re: DPF related error

Post by Rob_E »

I think that is what surprised me more, if it was measuring something it would have been less surprising for it to say it wasn't quite as clean as a new one, so didn't reset to zero. But as a theoretically calculated value it seems even more surprising that it didn't just go to zero when it was told it had been replaced. I guess it is harder to understand without being able to see what the calculations are it is doing in the background. Oh well, the counter is reset so at least the light is off and it will hopefully know it has more capacity than it did. Removing that much ash will hopefully mean there is less resistance to the exhaust flow than there was before.

That's an interesting point about the additive though. Does it always assume that more additive has been added when the particle filter is renewed then? I'd have to look again, but on the additive ecu, where I told it the DPF had been replaced, I thought there was a separate option to tell it that the additive has been topped up, I didn't do that one only the particle filter replacement. Though that option I think was labeled something like "additive topped up where low additive warning is on" or something like that. So does it always expect a full top up as part of the DPF replacement?

I couldn't see any figures for how much additive it thinks is currently left. But there were two counters; one described as counter 1, which I assumed was the total quantity added over the life of the filter, this was 201g and reset to 0 when I told it the filter had been replaced.
The other, counter 2, which read 83g both before and after the reset; I was assuming this was the quantity it had added since the last top up?
I couldn't see a current level, just a parameter "low additive level" which had a value of "not reached"
User avatar
GiveMeABreak
Forum Admin Team
Posts: 26065
Joined: 15 Sep 2015, 19:38
x 2992

Re: DPF related error

Post by GiveMeABreak »

Rob_E wrote:
20 Sep 2021, 18:26
That's an interesting point about the additive though. Does it always assume that more additive has been added when the particle filter is renewed then?
Not unless you tell it that the additive has been topped up.

These are 2 separate operations as topping up the additive is generally done at an interim period or checked by the dealer at a later service interval, so you would not be replacing the DPF just for that.

You generally find this operation in the engine ECU options. Once you've undertaken a global test, select the engine ECU and confirm then you will be taken into the other menus where this should be one of the options - or embedded within one of the other menus.
Rob_E
Posts: 7
Joined: 20 Aug 2021, 19:29

Re: DPF related error

Post by Rob_E »

GiveMeABreak wrote:
20 Sep 2021, 20:41
Not unless you tell it that the additive has been topped up.
Ok, that should be ok then I think. I didn't do that, I only told it the particle filter had been replaced. So the ECU should be inline with the actual level?
GiveMeABreak wrote:
19 Sep 2021, 23:12
...I'd also make sure you do fully top up the additive too while you are at it - as you have notified the engine ECU that you have done this. This will affect the warnings and calculations going forward and it is now expecting that the additive has been topped up.
Sorry, I think I must have got the wrong end of the stick, I thought in this post you were saying that when you tell the ECU it has had a new particle filter, that it also assumed that to mean the additive had also been topped up; and therefore I would need to do it now so the actual fluid level matched what the ECU expected.

Rob
User avatar
GiveMeABreak
Forum Admin Team
Posts: 26065
Joined: 15 Sep 2015, 19:38
x 2992

Re: DPF related error

Post by GiveMeABreak »

There are 2 separate things:

The filter itself over time becomes blocked with engine deposits, ash and elements within the additive fluid called Cerine. None of these can be burned off, so this leads to eventual clogging.

Specifically for the 'Cerine' mentioned above, the engine ECU estimates the amount of additive in grammes that has been dumped into the particle filter over time. When it calculates that the particle filter is likely to be saturated with Cerine and other deposits, based on the amount of additive that has gone through the system, it will start flagging the DPF warnings regarding changing it.

Back to the additive fluid itself, there is a certain amount (which varies from model and engine) that is filled at the factory and it starts estimating the amount of Cerine deposited in the filter as the vehicle is used. So when you top up the reservoir, you need to tell the ECU it has been topped up, as it is not physically measured (no float or measuring device). It then knows how much fluid is now in the tank which informs the low additive warning. It also estimates the amount of Cerine that has been dumped into the filter previously and knows how much more Cerine and other deposits the filter can take based on the top up.