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DPF related fault codes and searching for correct part

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Author Post
Tue Aug 03 2021, 04:39am
Member No: #16844
Joined: Dec 14 2010
Location: Ware
The engine management light has recently come on on my C4 (2005 2.0 HDI hatchback, currently at 188'000 miles), with the rather generic message on the display " depollution system faulty".
I've plugged it into Lexia and there are several permanent faults shown.

The first which has been there for a bit longer and seemed to be able to be present without the engine management light being on was:
"Additive system Fuel filler cap signal fault"

I have seen some posts on this and other forums which indicates this means it needs a new sensor to detect the presence of the fuel cap, when searching online I can find replacements with part number 1503T2 available that say they are for the C4. But I contacted one ebay seller and he said according to his data it was not compatible with my car. Are there that many variants of this sensor, would anyone be able to tell me what is the correct part number for this part on my car?

My understanding was that the additive system used the presence of the fuel cap to determine when and how much additive to add. Does anyone know what the lack of that signal would do? does it mean it would stop adding additive, or potentially add too much as it would just keep adding it to ensure there was some in the system?

The second and more recent fault is:
P1445: Additive system Maximum additive level in the particle filter reached.

What does this fault mean? Is it a consequence of the previous fault, and saying that it has been constantly adding additive to the fuel and now there is too much in the filter? This is what the local garage thinks.
Or am I right in thinking the DPF is a service item on these cars and you are expected to replace it with a new or recon one at some point; so is this message saying this is now due because over it's lifetime it has reached the limit of how much additive it can handle?

Thanks in advance

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