# Citroen C8 'Depollution System Fault/Failure'



## cartrouble (24 Apr 2010)

06 Diesel Citroen C8, bought it two years ago, all ok until around 6 months ago when this error first appeared as the engine cut out mid-drive (I have a mental block if the message says Depollution System 'fault' or 'failure').

Since then I've had it into a Citroen dealership who put it on 'the computer' and a long list of errors\faults came up, they said it couldn't be all of them and suggested the most likely was a problem with the throttle pedal. They put some code in and said to drive it again and if the error came up again to bring it back. The error & cutting out happened several times more and it went back to another Citroen dealer (just due to where it cut out the last time). 

They checked the computer again and said it needed a new throttle pedal thing (I'm not car-technical savvy). This was put in yesterday and today the car cut out again on the dual carriageway - same error.

So the car had to be towed and now has to go back to the garage. What do I do? Do I just keep pumping money into getting various bits fixed hoping that sorts the problem? I have no faith in the car now and with 3 young kids in the back and it's tendancy to cut out mid-drive I don't feel safe driving it. 

Would a Citroen dealership do a trade-in for a different brand second hand car, knowing it has 'issues'. Any advice welcome. Thanks


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## bobalong (24 Apr 2010)

Do they they mean the throttle / pedal position sensor?

Maybe a sensor in and around the throttle body. 

Is the car revving high when warmed to operating temp and while idle - maybe? Just a long shot from experience of this with other cars.

In most cases of this it means a new Throttle Position Sensor ( TPS ) or in a lot of cases a complete new throttle body (TB). 

On a throttle Body their are a few sensors connected to the engine management unit. Depending on the marquee - Sensors like the TPS above, a MAP sensor, a MAF ( Mass Airflow Sensor ) and an IACV ( Idle air Control Valve ) can be attached to the TB. The lACV could also be an issue for cutting out - as far as I know this dictates the amount of air being left into the inlet manifold. Sometimes these need a cleaning out - they get cluttered with carbon.

Normally you may have the air filter unit rubber piping attached to the Throttle body inturn attached to the intake manifold. I think the Throttle body replaced the concept of the old carburettor.

From another forum with a car that has engine cut out issues:

" .. This Idle air control valve is malfunctioning due to it being worn out or dirty. These are the classic symptoms of this ( cutting out ) and i would say 90% certain to be what it wrong. This valve only matters when you have not got your foot on the accelerator as it automatically supplies fuel and air to keep the engine ticking over"

Maybe off the beam totally, if I am others will swiftly correct me and the fact its a diesel engine - most of my experience is with petrol so Throttle Bodys and the like may not be present.

Bob


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## mathepac (24 Apr 2010)

The car may have a problem with the  diesel particulate filter or DPF, the purpose of which is to absorb particulate emissions (soot-like stuff) created when a diesel engine is started from cold. The soot is collected and stored in the DPF and then heated and burned off during one of the  regeneration cycles, as dictated by the engine control unit, ECU, and emission control systems, ECS. 

Generally, there are two types of DPF regen  cycles,  passive  and active.

For the passive DPF cycle to work, the car needs to be a driven a fair distance regularly at motorway speeds (2k to 2.5k RPM) in order for the DPF  to get hot enough to regenerate and safely burn off the particulates. 

If the car does mainly short runs from  cold starts and never warms up enough to trigger the passive DPF cycle, some cars have an active cycle where extra fuel is used to create hotter than normal exhaust gases to burn  off particulates in the DPF.

Given the complex interactions required between electronic systems in diesel cars and these poorly thought out and often poorly executed pollution control systems, problems with DPFs are not unknown, even in well-engineered cars like Audi and BMW. It may very well be a Citroen software problem, but I doubt it somehow as a lot of the hardware and software is generic (from someone like Bosch or whoever).

All I can suggest is that you try taking the car for a long brisk run at the week-end and see if that helps. If it doesn't  maybe someone can suggest a Citroen dealer or independent near you where the technicians know how to use and interpret the messages from the diagnostic equipment.

(I may of course be completely wrong, but it sounds disturbingly familiar.)


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## bobalong (24 Apr 2010)

Seems Mathepac maybe on the money re diesel particulate filter. Same issue but in a Peugeot:

http://www.peugeotforums.com/forums/showthread.php?t=347

Bob


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## mathepac (24 Apr 2010)

It's a possibility. A pal of mine fixed a DPF problem on a BMW diesel in a similar way to that described on the Peugeot forum above, but bad fuel, fuel filters, EGR malfunctions, poor maintenance, incorrect lubrication, etc are also possibilities.


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## cartrouble (24 Apr 2010)

Thanks bobalong and mathepac,

Interesting about the diesel particulate filter, it would make sense in relation to the nature of the error message. The car is mostly used for short runs and isn't even used every day so that adds up.

I will clarify exactly what they did with the throttle (at the time I was just glad it was 'fixed' )

I am making notes on the possible issues you have both outlined and the info from the Peugeot forum and will discuss with the garage in advance of doing anything else to the car. 

Much obliged for your input.


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## THENORTHSIDE (2 May 2010)

Have a C8 too , would reccommend finding a good citroen forum that have a C8 section as thats where I got most of the information to sort out the problems i have had with mine. Have brought mine to a main dealer and so far they have been just about ok but very very expensive ( bar a leaking diesel filter ). You could try getting onto to Citroen Ireland and talk to them as well. worked for me once in the past


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