307 1.6 HDi Filter block risk

[RichardW]

Last couple of days every time engine is started, I get the 'Risk of particle filter blocking' message. It had been on a few short runs round town on Sunday so thought it was just aborted, but it didn't regen today on work and back (60 mile round trip) where it normally does no problem. Stuck it on Diagbox thinking I would find something obvious, but nothing showing, no faults, no indication as to why it's put the light on! Pressure looks OK (so sensor not failed high as I thought it might). 230km (or is that miles?) since last regen, load at 64%, average re-gen 285 km, so it should do it tomorrow, if it can. My only wonder is that the additive load in the filter is showing as 107g, I wonder if that has passed some threshold, but again no code to indicate this is the case. There's no comms with the additive ECU (I suspect this a fault with the underbonnet fuse box) - engine ECU shows only 166ml of fluid left, but no message for low fluid level. Fluid was refilled before I got it at 80k, it's done 55k since then, it might be due again, but I'd expect a bit longer. All bright ideas welcomed!!

[EDC5]

That's interesting, I haven't had any issues with my FAP system yet but I always check the status of the FAP whenever i fire up Diagbox. I'm not sure what triggers the warning however it may be the case that it will trigger the warning without there being an immediate need for a regen perhaps?

Just a guess but the "risk of blocking the fap" message is generated as a result of parameters such as "percentage of time with engine cold in last 100km" and the like and may not be due to the pressure readings.

For some reason my car always shows filter load at 30% and it doesn't change however I average 400km between regens currently.

[Mandrake]

If there's no power to the additive ECU surely that would cause an issue ? If there is an additive ECU at all it must be designed to talk to one of the other ECU's to say what it's doing.

I'd start there...

[RichardW]

It's been like that since I bought the car, so I'm pretty sure it's not the cause of the current issue! It may cause problems in the future if it needs another Eolys refill - I think I've got a spare fuse box, should fit it I guess!!! There is a fault on the BSM that it is 'mute on the CAN bus' so I think that is the cause of not being able to read the ECU.

Reading about a bit it seems that it may just decide on the basis of miles / regen cycles / additive injection that the DPF is time served and put the light on. Seemingly you can tell it you have replaced the DPF and that will put the light out, but it may change the Eolys injection parameters which may not be best for an old dirty filter. So, I think cleaning of the filter is required, is on my (rather long ) list of jobs that need doing on the car. Running out of 'good' weather for doing it though!

If it regens on the way home (it didn't this morning) then I'll see what the revised parameters are. If it refuses to regen at present, then it may have to come off sooner rather than later!

[MikeT]

I have once had the risk of blocking warning and that was my oversight - I failed to fully reseat the MAF connector. A following scan showed a number of air related faults which once cleared and MAF properly connected, resulted in a successful regen straight after. I guess the warning appears as soon as a regen is due but is aborted, for whatever reason.

Certain conditions (I only know of three so far; continuous engine speed above a threshold, sufficient fuel capacity and engine temperature, maybe high electrical loads?) have to be met before it will authorise a regeneration. I don't believe I've ever travelled more than 35miles in a single journey since I've owned this car. When the regen occurs, soot loading is up to around the 68% mark. Here's the parameters I recorded (edited) a few months ago at the point a regeneration had completed.

Yes, rather annoyingly it records distance in km's. Mine is now averaging over 550km (was less than 350km when I got the car and I've been mindful to keep engine/emissions as clean as possible, including one forced regen (soot loading is now 0% after regens, when previously it was no lower than 3%).

The amount of additive in the filter is a record which you can compare to a table Citroen have published (Citroen Service of DocBackup) which indicates the assumed end-of-service of the DPF. IIRC, this was somewhere around 90g for most engines. It's a counter that will flag a fault code (maximum additive or somesuch) but can be reset. I reset mine just to clear the fault (which didn't inhibit regens btw) and all's good so far.

[EDC5]

I have once had the risk of blocking warning and that was my oversight - I failed to fully reseat the MAF connector. A following scan showed a number of air related faults which once cleared and MAF properly connected, resulted in a successful regen straight after. I guess the warning appears as soon as a regen is due but is aborted, for whatever reason.

Certain conditions (I only know of three so far; continuous engine speed above a threshold, sufficient fuel capacity and engine temperature, maybe high electrical loads?) have to be met before it will authorise a regeneration. I don't believe I've ever travelled more than 35miles in a single journey since I've owned this car. When the regen occurs, soot loading is up to around the 68% mark. Here's the parameters I recorded (edited) a few months ago at the point a regeneration had completed.

Yes, rather annoyingly it records distance in km's. Mine is now averaging over 550km (was less than 350km when I got the car and I've been mindful to keep engine/emissions as clean as possible, including one forced regen (soot loading is now 0% after regens, when previously it was no lower than 3%).

The amount of additive in the filter is a record which you can compare to a table Citroen have published (Citroen Service of DocBackup) which indicates the assumed end-of-service of the DPF. IIRC, this was somewhere around 90g for most engines. It's a counter that will flag a fault code (maximum additive or somesuch) but can be reset. I reset mine just to clear the fault (which didn't inhibit regens btw) and all's good so far.

hmm, that's got me curious now. I'll head to the car and see what parameters mine is recording, especially the "amount of additive in filter" (although the car hasn't done 60k yet so it should be low-ish).

Do you happen to know what role the EGR plays when a regen is taking place?

[MikeT]

hmm, that's got me curious now. I'll head to the car and see what parameters mine is recording, especially the "amount of additive in filter" (although the car hasn't done 60k yet so it should be low-ish).

Do you happen to know what role the EGR plays when a regen is taking place?

No I don't, sorry.

[RichardW]

I imagine that the EGR is closed during regen as its function when open is to promote lower combustion temps, whereas you want it as high as possible during regen (hence closing off the intercooler on some models during regen).

No regen on mine this evening as far as I could tell - although it decided to be dry this evening, so the most obvious pointer, HRW being on, was not visible, but I didn't notice the slight rough running / increased fuel consumption I normally notice when it's regenning!

[RichardW]

Meant to say, interesting info Mike. Still no regen.... I'm a bit sus about the mileages recorded, as I reckon it does it about twice a tankful of diesel, ie about every 300 miles (so 500km). I'll stick the computer on again tonight and see where it is up to. I think one of the other inputs is the exhaust temp upstream of the DPF - thinking back, this was showing as <100°C even after 10 mins of idling when I was checking, maybe this had gone belly up and is preventing re-gen. I'll try and check it when it's hot when I get home tonight.

[MikeT]

I do know Richard, that the exhaust temp will cool right down when idling, even if it's just been ragged, it's extremely variable according to loading. IOW, be sure to observe EGT while driving it hard, it should get up to 300c or more. I can recommend using a free screen recording program (very low resource) called SRecorder so you don't get distracted while driving. If it goes up to 4/500c you know a regen is in progress.

[EDC5]

These are the screen grabs from yesterday, I think the upstream temperature sensor is broken as the car was stone cold?

From the looks of it the additive has been topped up once before.

When I started the engine I noticed about 5 mbar of pressure across the FAP which I assume is OK?

I also found a great youtube video and the FAP system, It's in French, but the diagrams and animations are pretty good

[RichardW]

It regenned it yesterday seemingly without me noticing... up to 50% load after 150km, so it looks like it's not working that well, the car has just decided it is EOL! Was going to clean it anyway when I do the cambelt, just need to find the time and the weather to get a-round-tuit!!

EDC5 - 5mbar at idle is OK; ref the temperature it's possible that it only goes down to 100C - mine was just saying <100C

[EDC5]

EDC5 - 5mbar at idle is OK; ref the temperature it's possible that it only goes down to 100C - mine was just saying <100C

That makes sense, a high temp probe probably bottoms out around 100 then

I'll keep an eye on the pressure, see if it increases long term.... I know what to do ......

[demag]

I can't believe the muck coming out of that car. I thought the idea of fap was NOT to pollute the atmosphere. Incredible.