Warning "Risk of particle filter blockage" - C5

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Richard Stevens
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Warning "Risk of particle filter blockage" - C5

Post by Richard Stevens »

Carrying on (maybe) from my 'Anti-pollution' episode, now getting the above message on each start-up. Motor is a 2005 C5 II 1.6HDI.
I have had the car extensively checked in France (where I was when it first appeared), and they tell me there is nothing wrong with the DPF or its pressure differential switch, which they substituted temporarily (the switch, that is) to aid diagnosis. They also redid the electrical connector.
During testing there were strange, non-linear figures on the DPF pressure difference readings, from 0.3 mb up to a highest reading that I saw of 53 mb.
They carried out their investigation for about 1 1/2 hours, then said they didn't know what was wrong, but that it was probably a false warning.

Any ideas, please? I did recently remove the catalyser and DPF and pressure-washed them.
Have checked the lower hose which seems fine, holds pressure and is clear.
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Re: Warning "Risk of particle filter blockage" - C5

Post by Lighty »

I have seen unusual dpf readings, if the pressure sensor pipes are fitted the wrong way around.
There will be risk of blocking if the turbo boost is not as it should be, maybe also low on Elloys fluid.
If you are getting that error message , there must be a fault stored.
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Re: Warning "Risk of particle filter blockage" - C5

Post by cachaciero »

The diff "switch" is not a switch, i.e two state device, it is a sensor and measures actual pressure across the dpf, 53 mb is high and would likely give you the warnings that you get. However you don't say at what revs these pressure readings were taken. The pressure will vary both with amount of gas going down the pipe and the state of the DPF. The amount of gas going down the pipe will increase with revs and load.
If the variation in pressure you were seeing was at idle then such a variation can only be due to a sensor error but if the pressure readings were at two different values of revs then they may well be correct values in which case I would be suspicious of 53mB (assuming measured at the higher rev range) in that it seems high and could well indicate a partially blocked DPF. When was the DPF last changed? if getting close to 100K since last changed / cleaned then I would think it very likely that it is on the way out.

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Re: Warning "Risk of particle filter blockage" - C5

Post by Richard Stevens »

Thanks for your replies.
The pressure readings were taken across the rpm range, with the engine being raced when the highest readings occurred. At idle it was invariably below 0.5mb. Can't say what the highest rpm reached was, but there were many 'cycles' and I only saw 53mb once.

It doesn't look possible to fit the pipes reversed, the top (upstream) one being so much shorter.
During testing I saw that there was plenty of Eolys fluid remaining in the tank (3000ml).
I haven't had the memory checked since I came home, but will do.
The car has done 67000 miles and runs fine except for a long-term hesitation at around 2000 rpm.
Yesterday I spoke to a local Citroen specialist garage, and was advised that there may well be a problem with the EGR valve, but before going there I'd like to be a little more sure that it won't be a wasted effort.
Anyway, I shall find out the recorded fault and see where we go!

Cheers, guys.....
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Re: Warning "Risk of particle filter blockage" - C5

Post by fcfukaus »

EGR valves can give hesitation in the engine around the 2000 rpm.

EGR test: disconnect the pipe from the EGR and attach a vacuum pipe - should hold vacuum - any loss then needs repair or replace - I have repaired my EGR by taking it apart and smearing high temperature gasket sealant over the diaphragm then screwing it all back together and works fine for 40K. EGR valve should click shut when approx .5 bar vacuum is released suddenly.

EGR solenoid test: attach a vacuum pump pipe to the pipe from the solenoid - start the car and idle - vacuum should be around 1 bar then settle back to zero - rev the car and vacuum should increase to about 2000 rpm then drop as the solenoid activates - this is for a 2.2 2005 HDI so vacuum levels may vary

Standard procedures for all particle filter and limp mode problems (often errors will not be showing or error that is recorded relates to something else):
> check EGR as above
> check all vacuum pipes for any breaks/leaks - use a vacuum pump for vacuum when car idling and individual pipes holding vacuum when car not running and pipes disconnected and ends blocked
> check all solenoids are activating correctly - few ways of testing and cleaning these
> check vacuum movement of turbo
> check pressure differential sender - use a Lexia (ignition on but engine not running) and read parameters - disconnect low pressure pipe and connect vacuum pump - create small vacuum - check millibar reading on Lexia and compare with vacuum pump - check the high pressure side as well using either a vacuum or very low pressure (no more than 100 mb)
> extra test for the differential sender - take off high pressure pipe - put in a T then reconnect and run a pipe into the cabin of the car with an automotive pressure gauge - go for a drive and watch the pressure go up and down as the motor is revved - Lexia can do this as well if you have it on a laptop - particle filters are loaded if reading approx 117 mb and need regeneration/cleaning if readings persistent or even replacing
> check turbo pressure - simple way to do this on the C5 is to cut the small hose that goes from just before the intercooler to the small sensor - put in a T - once again feed a long pipe back through the passenger window with the pressure gauge on the end to check the pressure as you drive - leave the T in and blank the pipe so it is there for any future testing
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Re: Warning "Risk of particle filter blockage" - C5

Post by Richard Stevens »

Thanks for latest input - and apologies for my misunderstanding the point about the hoses being wrongly connected. Only the downstream pipe was in fact taken out of the car, so I'm happy they're not wrong.

There is no recorded fault in the car, but the Snap-On branded diagnostic device claimed the particle filter is 80% blocked. Sounds bad...

I shall proceed with inspection and cleaning of the EGR valve and what testing I can manage - I'll have to borrow a vacuum pump.

If that doesn't improve things I'll remove the DPF again, give it a better clean. In the meantime I've put some Wynn's DPF cleaner in the fuel, more in hope than expectation.

Cheers, Richard
1995 ZX Turbo diesel Volcane
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2006 C5 2.0 HDI Exclusive
Remember - many warnings are spurious or bad connections
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Re: Warning "Risk of particle filter blockage" - C5

Post by SaabC5 »

Richard, have you seen this product i found on eBay, it might be worth a throw of the dice.....

http://www.ebay.co.uk/itm/JLM-DIESEL-PA ... 3299434044
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Re: Warning "Risk of particle filter blockage" - C5

Post by fcfukaus »

Sorry to readers

Forgot to say to put diesel in the additive tank to top it up if you are getting low additive warnings - reset the system with a Lexia.
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Re: Warning "Risk of particle filter blockage" - C5

Post by Richard Stevens »

That's a very elegant and simple DPF work-around. Not sure I'm quite ready to remove the DPF and go without, but I appreciate the solution and the time may come!

I removed the EGR valve last week, found much soot in it. Cleaned and refitted it, some acceleration improvement, but still the "risk of filter blockage" warning.

Today I removed and pressure washed the DPF again, and got what seemed to be loads of soot out. There is again some improvement in acceleration, but still the blockage warning.
I have an idea that there is no Eolys fluid getting into the fuel - evidence the apparent 3000ml remaining (according to the French Lexia) after 67000 miles.

We all know that the fluid is added with fuel cap removal/replacement, but does anyone know anything about the actual system, what's in it, what powers it, and what could go wrong with it?

cheers, R
1995 ZX Turbo diesel Volcane
1999 Xantia HDI
2005 C5 1.6 HDI
2006 C5 2.0 HDI Exclusive
Remember - many warnings are spurious or bad connections
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Re: Warning "Risk of particle filter blockage" - C5

Post by Richard Stevens »

Further to my last, do any of you guys know how the Eolys system can be checked/tested? (The checks in France identified 3 litres of fluid still in the tank after 67k miles).

How can you tell if it's not working? - is it possible to hear the pump running?
Is there a fuse or relay in the system?
Naturally the handbook is useless here, as is the Haynes manual, which barely acknowledges the system's existence.

The "risk of filter blockage" warning turns up like a faithful dog every start-up and the engine runs better than ever now I've cleaned the DPF.....
I also did reverse (temporarily) the upstream and downstream pressure lines to the differential sensor with no result,
1995 ZX Turbo diesel Volcane
1999 Xantia HDI
2005 C5 1.6 HDI
2006 C5 2.0 HDI Exclusive
Remember - many warnings are spurious or bad connections
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Re: Warning "Risk of particle filter blockage" - C5

Post by skimy »

Hi...

Another DPF problem here!

I bought my C5 1.6 (2005) in August, with 105 000 kms and after a few weeks I got the "Risk of particle filter blockage" too.
Drove to Citroen dealer, they said the DPF was dead and it had reached the maximum attempts of regen, so they replaced the DPF and also refilled the Eolys tank.

500 kms later, same message. I went back to the Citroen and after a lot of tests they said the Eolys wasn't being injected as it was supposed too, causing the regen process to fail. How to solve this? Replace the eolys injector...wich is part of the Eolys tank and, being a "1-piece" thing, the whole tank had to be replaced (auch...)

500 kms later...same message. I called the same guys and they said sometimes this was normal (yeah right) and to keep driving and see if the message kept appearing. 500 kms later and the regen was succefully done (I instaled a LED, next to driver's side mirror, to be aware of the regen process) and I thought the car was finally ok. Wrong!

More 500 kms, more error messages. I read that sometimes glow plugs are dead and this error might be related to that, so I changed the glow plugs even thought Citroen dealer saying this had no relation do DFP regen. Turns out all plugs were dead! I run a diagnostics test and ran a check on many components, including the glow plugs relay, wich was fine.

Today I was driving at 80 km/h and the message came up again...I don't know what to do anymore. I just found out about some "dpf sensor" that may be dead on malfunctioning if the pipes are connected the wrong way, I'll try to check this tomorrow.

Besides this sensor, is there any other thing to check? I'm really upset about this whole thing, and I don't like the "drive a few more miles and see if the message keeps showing" approach, as I think it might ruin the DPF again and/or have some bad consequences to turbo and god knows whatelse x)

Merry Christmas by the way :)
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Re: Warning "Risk of particle filter blockage" - C5

Post by Lighty »

You really need to get the car on a diagnostic machine. You have little chance of repair without some useful information..
Enjoy your Christmas:)
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Re: Warning "Risk of particle filter blockage" - C5

Post by citroenxm »

I got a risk of blockage on my 1.6 hdi.. but my wastegate vac solenoid was faulty and was giving overboost ... I fitted a replacement vac solinoid.. that lives down the back of the engine above the drivers side driveshaft and the problem has gone away... so id not point at the dpf directly... check the vac solnoid for the turbo....
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Re: Warning "Risk of particle filter blockage" - C5

Post by skimy »

But how did you found out the vac solnoid was the problem?
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Re: Warning "Risk of particle filter blockage" - C5

Post by citroenxm »

I had lexia on the car and read the fault codes.. but also knowing the hdi like I do the ecu always goes into limp mode on over boost. . But it wont with underboost if the wastegate stays open...
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