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2.2 HDi Antipollution Warning - alfie2
Does anyone know of a cheap alternative to fix the problem as citroen want £500 for new filter and oil
2.2 HDi Antipollution Warning - bell boy
yep sell it (not a lot of people know that) ;-)
2.2 HDi Antipollution Warning - dieselnut
Most of what you need to know is on this thread -


Decide for yourself.
2.2 HDi Antipollution Warning - Screwloose

That is quite cheap for a FAP filter, tankful of Eolys and system recalibration - there's many dealers charging nearer twice that.

What's the problem? Everybody demanded cleaner cars - now here's your chance to contribute to the greenoidery.....

Bit surprised that you're not pleased.....
2.2 HDi Antipollution Warning - Armitage Shanks {p}
I undrstand that the Particle filter can be dealt with by

a. A forced regeneration
b. By Being pressure washed
c. Replaced with an exchange unit at under £200

Agreed, the EOLYS is costly
2.2 HDi Antipollution Warning - Screwloose

A forced regen is needed if the FAP is merely over-loaded; this sounds like the routine replacement of the FAP on mileage as tank refilling is also mentioned. They do become clogged with non-combustible residue after a lot of use.

Pressure washing has been supeceded [in the UK] by FAP replacement on health and safety and waste regulations grounds.
2.2 HDi Antipollution Warning - NVH
I was quoted £350 by a franchise garage just 3 weeks ago ,
That includes an exchange/recon filter.

I changed the filter on my last C5 (51 plate) at 52k approx.
My current C5 (04 plate) had a false alarm on the antipollution message at 41k
due to a lot of short trips with low mileage.
This was due to a "swirl pot" / diaphragm needing replacement probably leading to overfuelling. Under £70 to fix.

New generation facelifted C5s = mainly 05 plate on - need the FAP change only from 75-80k on.

The exact mileage depends on fuel economy as the Eolys fluid is released.

I currently get 42mpg in normal use. Although the German autobahn this weekhas knoecked the economy for 6 :-)
2.2 HDi Antipollution Warning - catlady
I've had the 'diesel additive low', 'diesel additive minimum' and 'change diesel filter' messages for some time on my C5 2.2 and have been horrified at the charges by dealers, the current mileage is 70,000. I have been told that Millers diesel additive will sort the problem.
Has anyone tried this, does it work, is it advisable?
If the filter and eolys are not replaced by a dealer, will the message still show if the computer has not been reset, if so, can it only be reset by an authorised dealer?
2.2 HDi Antipollution Warning - Screwloose

Do not be led astray by armchair experts into causing a serious problem with your car. Diesel addive will do nothing for this problem.

Once the Eolys has run out, the FAP regenerations cease. This will inevitably lead to a totally blocked "cat" and unforseeable damage.

Yes; this is a rip-off - but all the greenoids demanded it and now you have to grin and pay-up. Everyone thinks these emission "improvements" are a fine idea - as long as they don't have to pay..... [And this is only the beginning.]

If anyone other than a dealer [or other specialist] tries to mess with the system it will not work. The electronics have to be re-calibrated by someone with authorized access; no exceptions.

Shop around the dealers - there's a wide variation of charges for; new FAP, empty and refill Eolys and reset additive injection computer. Anything up to £900 is not unheard of.
2.2 HDi Antipollution Warning - Chris M
Does the Renault 1.5dci use the same type of system? I know they have low emissions and consequently the low road fund licence, but at the costs mentioned here, you would need to stick some funds aside to pay for the extra maintainance.
2.2 HDi Antipollution Warning - Crinkly Dave
And is this system fitted to the 1.6 Focus diesel. Need to acquire cheap and reliable car for next 7-8 years to allow for divorce and re-mortgage etc, and choice is Yaris/Corsa/Punto diesels, or a bit bigger Focus/C3/Fabia diesels.
2.2 HDi Antipollution Warning - Screwloose

There's no certain answer to which engines, in which cars, on which years, use a FAP or DPF - but the ones that don't are getting rarer.

It's always worth checking before buying if that particular example needs regular emission kit servicing.

I've not - yet - seen a 1.5DCi with a FAP; but if the Focus is the PSA unit then there's a good chance that it will. [Even though some 307 1.6s still use the HDi, not the HDiF.]
2.2 HDi Antipollution Warning - citroenslave
Citroen 2.2 HDI Particle Filter. Cleaning the filter & replacing the additive.
Anti-Pollution Fault warning. Info here is for a 2.2 HDI Estate.
Thanks to all who wrote on above, especially Dieselnut. I had this fault up for 2 weeks (driving on limp home mode) while gathering info on how to solve it. Yes the filter can be cleaned & the fuel additive added. The usual safety rule with Citroens! Don?t go under them unless you have them safely on axel stands.
You can split the particle filter by opening the four 13mm hex nuts (spray with pen oil a few times and allow to soak for a while) around the middle of the filter. Think its best to use a six rather than 12 sided socket for these. Remove the exhaust clamp on the back end of the filter. The exhaust pipe is inserted into the filter approx 40mm. Remove the small pipe fitted into the side of the filter at the back 19 mm hex.
Once removed soak the filter for a few hours in water and pressure wash from both sides several times. It?s a slow job. Be careful if you are using an industrial high pressure washer, the high pressure can remove the glue from between the segments inside the filter. Think it might be best not to use detergent. Water from an ordinary garden hose should easily flow through the filter when finished. You can use compressed air to blow the water out the filter before refitting.
Refitting: Clean the gasket and the mating flanges & refit the filter. I would suggest running the engine at idle speed for a while to allow the filter to dry out.
Replacing the Additive: The additive tank is underneath the fuel tank on the left side. The filler facing to the rear. Press in firmly on the two white buttons on each side of the cap and pull the cap off. I could only get it form the Citroen dealer ?50 (£34) per litre. If you have the RP # (you?ll find on the drivers side door frame near the hinges 4 digits & 2 letters it makes getting the correct additive easier.
Kits came with extra bottle & tubes & no instructions. I used an 18mm inside diameter clear plastic tube which fitted over the addative tank opening. I routed this up inside the wheel arch and fitted a large funnel into it. You can hang this tube & funnel off the door lock receiver. This worked perfectly with no venting problems. The clear hose allow you to see if you are overfilling.

2.2 HDi Antipollution Warning - TurboD
or stick with petrol for an easily life?- this sounds horrendus, much harder than changing a petrol cat on a car. Good to know about it though.
2.2 HDi Antipollution Warning - Greg R
It is probably worth going to France to a garage to get this sorted out. They have loads of citroen out there! I know if you are ill, a day trip to a french doctor/ hospital is a good idea!
2.2 HDi Antipollution Warning - Luc

I have this message since I buy this car 2 weeks ago: Citroen C5-II 1.6HDI from 2005, 110CP with 110.000km .
I drived ~850km, without any engine problem, it have power, drived at 140km/h without any engine problems power/torque.
Got to Citroen dealer for diagnostics and they told me that FAP need to be replaced, the price they told was a little to big so I try to save some money in December.


I used your instruction ( to clean ) and Citroen diagrams to remove the filter.

Cleaned 2 hour with cold water on good and high pressure, sinked over night in cold water and next day again cleaned >3 hour with hot & cold water until I removed any trace of ash. Water it is flowing nice from one side to another on the filter, no blocks.
Dried with pressure air and refitted to my car but I still have this message "Risk of filter blocking". Drived 40km and still the same, car it is working OK only that stupid message.

Any idea please ?

Cleaning pressure pipe from FAP to pressure sensor, maybe even changing the sensor or only chance is to change the FAP ?

pictures here:
h ttp://i220.photobucket.com/albums/dd237/L_DM500s/DSCF2313s.jpg
h ttp://i220.photobucket.com/albums/dd237/L_DM500s/DSCF2302s.jpg

h ttp://i220.photobucket.com/albums/dd237/L_DM500s/DSCF2317s.jpg
h ttp://i220.photobucket.com/albums/dd237/L_DM500s/DSCF2314s.jpg

Edited by Luc on 19/12/2007 at 23:28

2.2 HDi Antipollution Warning - Screwloose

You've only done a small part of the job. Once the warning has come up, the system must be re-set by the dealers, or somebody with the right equipment.

You also have to replace the Eolys fluid in the tank and recalibrate the fluid quantity amount.

The flushing water from the FAP is rated as toxic waste; I hope you disposed of it at a proper facility.
2.2 HDi Antipollution Warning - Luc
I have the impression that for additive level it is another message, and message "Risk of Filter Blocking" will gone by itself after the filter it is not more blocked... because this message appear only after the engine it is started and not before, and I think that this message it is generated by pressure sensor from FAP.

The Eolys will be topped up by Citroen Dealer, I don't want to mess with that stuff because I know that level must be updated by dealer using Lexia sw.

I hope that the flushing water from FAP it is not so toxic to affect me when I cleaned this filter, and yes it is 100% proper disposed... in city drain together with others toxic wastes from other citizens.
2.2 HDi Antipollution Warning - adverse camber
some info on the c8 forumhere

also the frenchcarforum - which was missing last time I looked for it
2.2 HDi Antipollution Warning - Screwloose

Once the system has flagged a fault; it often shuts down until properly reset.

As usual; I see it's only the UK that spends lots of money complying with the EU waste Directives....
2.2 HDi Antipollution Warning - Luc
I expect also that car manufacturer to label proper all car parts according to EU Directives if that parts expose a danger to health or environment...

In car manual it is no warning about FAP hazard to health or environment and also nothing stamped on FAP filter itself except the serial nr and production date ( on metallic part of course ).
2.2 HDi Antipollution Warning - Screwloose

FAPs are returned in sealed packages to the manufacturers for recycling. There's very little washing-out done now as the costs of labour/staff protection/disposing of the water makes a new FAP cheaper and safer.

Waste management is now mostly just a money-making racket; but - at least in the UK - the penalties for non-compliance will make your eyes water.

Regardless of varying views of what's actually in it; I cannot see that it is responsible for this forum to advise dumping EU-listed toxic waste to the environment, just to save money.
2.2 HDi Antipollution Warning - dieselnut
Luc, you are correct in that when the particle filter is clear, the 'unblock diesel filter' message will reset on its own. Did you tighten the presure monitoring pipe up ok after re-fitting the filter? The 2 metal pressure pipes from the filter join to 2 rubber pipes in the engine bay, these have been known to split.
The 'low diesel addative' message will remain even if you refill with Eolys, but the Eolys fluid still pumps ok with the alarm message displayed. So if you can live with the odd alarm message, don't worry about it.
2.2 HDi Antipollution Warning - Screwloose

You are correct for early versions of the software; but there have been several updates to the additive ECU's programming and it may not always be the case on the later cars, or those that have had downloads in service.

I've seen many cases where the FAP simply blocks from lack of regeneration if the additive quantity has not been reset successfully in the ECU. This is a particular problem on 307s and 407s.
2.2 HDi Antipollution Warning - Luc
I think I will go to radical things if the message/car will start to annoy me...

check my post here about my idea how to disable the FAP system:


and if you want to study the FAP documentation here it is:



2.2 HDi Antipollution Warning - Screwloose

Your whole idea falls flat at the first line. There's no point in feeding the Eolys back into the additive tank because there isn't a level sensor.

The system is told how much it has in the tank at re-fill and then subtracts the quantity it's injected into the diesel until it has used that amount. It won't know - or care - that it's tank is still full; once it's pumped a tank-full, the system stops.

Drilling holes in the FAP is also pointless; the back pressure at idle would be a lot different to full power.
2.2 HDi Antipollution Warning - Luc
ok forget for the moment the Eolys tank... that one is not important at the moment

Driling holes in FAP without first hack the pressure sensor it is pointless yes.

As you seen in documentation graph the pressure it isn't fixed value will be between a-b value.
I have to see what the car will think if the pressure sensor will give only one good fixed value... ( maybe this case it is close to a brand new FAP filter ) maybe somebody with Lexia can do some experiments and read the error messages ( if are some errors ) experimenting this idea.

I just check now the value from pressure sensor
3 - RED - VCC 5V constant.
2 - White - GND
1 - Orange - V from Sensor mesurement:

now I have V = 0.534v and I have Risk of filter blocking....

If the V = 0v then I think this mean pressure sensor is damaged or disconnected...

First, for testing I can put a variable resistor and increase the V to see if the "risk... " message will go I think V will increase if the filter state is ok, regenerated...

I also think I can program a micro controller to emulate the normal values for idle and high speed.
I just need to connect at that wire my digital voltmeter & laptop and make a run with the car to acquire more data and analyze the variation graph.

I think I can use also the actual pressure sensor as it but with the micro controller to limit the voltage he will send to computer. Let's say he will not be able to tell that the filter it is perforated, completely blocked, or partly blocked...basically the micro controller will increase the value of V with a fixed value I have to find.
2.2 HDi Antipollution Warning - Screwloose

It's just a car. In fact it's just one of the many grubby bits of a car. Cars cost money to run and this emissions stuff is just part of the costs now.

Wasting that much time and money finding implausible ways to try and fool the additive computer smacks of obsession.

2.2 HDi Antipollution Warning - dieselnut
Luc, I tried similar dodges when I had this car, as I was very disapointed with the fuel consumption after my previous XM2.5TD.
The system is very complex & seems to look for different exhaust pressures depending on the throttle setting. If it doesn't see what it's expecting it goes into limp home mode. I didn't go into complex electronic add-ons as you are suggesting but I think you will struggle to beat the system. The only way might be if you could re-prog the ECU telling it no particle filter fitted, if that is possible. You need someone who knows the ECU programming inside out. But as Screwloose says, life is too short. I bought a far simpler Passat 130 after have nothing but Citroens for the last 25 years & am now back to decent MPG again & simpler engine.
2.2 HDi Antipollution Warning - Luc
I hooked my digital multimeter to laptop and FAP differential pressure sensor and took a log from a 15km ride.

Today conclusion it is:

- value from previous post, ( my first quick measurement ) was wrong because I think I used bad GND, now I used GND from wire that come to sensor.

I can say that voltage it is almost stable at 4.64V no matter what speed I had ( max speed 130km/h ).

for a long time was no variation at all from this value 4.64V; any way variations are very small and V never dropped under 4.2 V more than 1/3 sec.

I will run more tests until I will be able to get the final conclusion.


2.2 HDi Antipollution Warning, solved. - citroenslave
My Antipollution Warning returned & car in crawl home mode most of the time.
I was under my car checking if littel plunger which indicates vane movement on the turbo was moving & I found a crack in a little rubber tube on some kind of actuator close to the turbo. I cut off the cracked end of the tube, fitted the rubber tube back on & all faults were gone. No problem for last 5K miles.
2.2 HDi Antipollution Warning - 205stdt

Hi, any chance you could give me more details (loads loads more) as I have just bought a nice looking very clean 406 hdi coupe and the fap warning symbol keeps appearing - 03 on 77k. Also is there a much cheaper alternative to this eloys crap, or a much cheaper source. Re the dpt, is there any wiring diagrams of this and also a sensor make and model - you mention 5v so I assumes it’s a 2 wire screened 0-5 volt transducer. Is the low side to the outlet and the high side to the inlet of the filter? What about the temperature, is there a separate temperature sensor – what type/output. As you say it would be handy to map the sensor outputs from new or clean filter and mimic this with some circuitry to trick the ecu. However despite that I am told the counters still need resetting by pug and so I bet I’m last in a very very very long queue to be able to hack into pugs ecu computers and reset them/ disable them with my laptop without planet 2000 or whatever they use that costs 6k or so. Last, is there any info on the glue in the fap – cant it be cleaned with some solvent that doesn’t attack the glue? Regards Honest I am John

2.2 HDi Antipollution Warning - big_G

Hi, if you have problem with DPF, FAP or other symbols, dont worry. I`m removing that filter and installing a chipbox which send information to FAP computer. Also you dont need to worry about changing FAP filters and filling EOLYS on the future. Car with that system was checked on MOT, and exhaust emission was accepted. Chipbox with installing and resetting cost 300£. Installing takes about 4 hours. So, up to you ;)


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