Yet another "depollution system faulty" Citroen C5 X7

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Yet another "depollution system faulty" Citroen C5 X7

Post by citroC5 »

Hello everyone,

Before I began writing this, I typed "depollution system faulty" into the forum search function and OMG! Sooo many answers! Sifting through them, I saw a lot of them to be 1.6Hdi-related, but none seemed to fit my set of symptoms, so here I am.

First and foremost, it's a June 2008 C5 X7 Tourer, 1.6Hdi with 282000km (175000 miles) on the clock. DPF was removed and cleaned by specialists on the 28th January 2020.

Message will pop up when I give it prolonged beanage. The other day I had to accelerate hard to get out of a spot of bother. The engine wasn't up to temperature, and the revs were around 3000rpm for about 10 seconds, and that was enough for the message to appear. It popped up the 2 or 3 times I started the car that day, but disappeared the next day by itself.

Today, I did about 25 miles at a steady 60-75mph, and up a hill at around 2500rpm, there it is, the sodding "depollution system faulty" message.

I've taken the car to a mechanic but he said "ah it's nothing" which was his way of saying "get lost, I can't be bothered", and erased the codes. I want to take it to a Citroen specialist but he's miles and miles away and this lovely forum could help as it has so many times before, that would be splendid. I'm always grateful for the knowledge I pick up here. Thanks in advance.

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Re: Yet another "depollution system faulty" Citroen C5 X7

Post by GiveMeABreak »

You need to provide us with the fault codes - which will be logged in the engine ECU (before he erased them), but if you have the message again, then the fault codes will be triggered again.

We really need these as otherwise it will be pure speculative guesswork. E.g. Pressure Differential Sensors, DPF filter still blocked, EGR stuck / sticking, Wiring, other Sensor, Electrical, Additive Pump / etc., etc. So you get the picture.

Another thing, when had your DPF cleaned the last time, did the garage inform the Engine ECU that the filter had been replaced? As long as it was a full and proper deep clean, they should of told the engine ECU the DPF had been replaced, as it keeps a record of how much additive has been dumped into the filter. Here I mean the Cerine components contained in the additive liquid that cannot be burned off during regeneration - it is these that ultimately block the filter along with other deposits.

So the engine ECU estimates and tracks how much additive (in grammes) of the unburnt Cerine it thinks has entered the DPF over time and when it gets to a certain amount it can also trigger a warning as time to replace the DPF (or deep clean it). So that's why the engine ECU has to be informed that you have replaced it - or it will still think you have the old filter on.

These are just a few pointers, but any fault codes may be useful.

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Re: Yet another "depollution system faulty" Citroen C5 X7

Post by RichardW »

When was the last time the fuel filter was changed?