Filler cap fault issue

[Tim1968]

Hi,
New member here who recently bought a 2008 Citroen C5 1.6HDI VTR+ 110BHP. I have an issue that hopefully someone can guide me in the right direction.

A few days ago I filled up with diesel and when I started the car up I had the service light com on and the error message of 'Risk of particle filter clogging'
I took it to my local mechanic and left it with him and he plugged it in and when I picked it up he said that the error was that there was 'no communication from fuel filler cap' as a permanent error,
He suggested this could be a faulty filler cap, sensor or wiring. So my question is; has anyone had this issue, is it more likely a sensor issue and if so what part number am I looking for.

Thanks in advance for any help.
Tim

[GiveMeABreak]

There is a harness connected to the fuel filler cap that detects when the fuel cap is opened, so the engine ECU knows that fuel may of been added. If it deems sufficient fuel has been added it will instruct the diesel additive pump to inject a certain amount of additive into the fuel tank.

So you may have an issue with the cap, the plug detect harness or something else, so if you have any fault codes, pop them up for an explanation.

[Tim1968]

Hi Marc,
Thanks for the response.

Sorry Wasn't given a fault code just those details by the mechanic. Yes he implied the 'risk of clogging' error was due to the ECU not knowing to add additive after filling. I'll message tomorrow to see if he remembers what code it was.

Tim

[Gibbo2286]

One fairly common problem is the magnets in the cap fall out, something you can easily check yourself.

[Tim1968]

Hi Marc,

Only one fault code coming up and this is what the OBD2 reader is saying;
P2408
Raw code:2408
ECU: Engine control unit
Status: Confirmed
OBD11: Fuel filler cap warning sensor/switch - circuit malfunction

Tim

[GiveMeABreak]

Here's the descriptor. nothing much than we've already suggested, so check magnets and harness / harness connections.

Fault Code:	P2408
Description of Fault:	Additive system : Fuel tank cap sensor signal fault. The engine ECU detects an incoherence on the additive reservoir cap signal.
Conditions for Fault to clear:	Ignition on
Downgrade Modes whilst Fault is active:	-
Symptoms:	-
Suspect Areas:	Additive adding

[Tim1968]

Cheers for the quick response.

Stupid question how do i check magnets? and if it is that can magnets be supplied and fitted or is it a new filler cap?

[Gibbo2286]

Cheers for the quick response.

Stupid question how do i check magnets? and if it is that can magnets be supplied and fitted or is it a new filler cap?

just open the lid and look inside there should be two small magnets opposite each other at the edge.

[Tim1968]

Cheers. I thought that would be the answer. I've had a look and they are there.

I've been looking and a car dismantler only 20 minutes away has a 2012 1.6hdi vtr+ they are breaking would the filler cap and/or harness and connections be the same as my 2008?

[GiveMeABreak]

Just about all the diesels with particle filters have the same plug detect harness. Be aware that these are no longer available from Citroen now, so if it is your harness, it will need checking the wiring connections and repairing if necessary or a replacement if you can get it.

[citroenguy]

Is the filler cap is ok, i'd remove wheel arch liner and check wire and connections for corrosion.

Is this a mk2 or mk3 C5?

[Gibbo2286]

The sensor at the filler cap end is really not much more than an on/off switch activated by the cap magnets, it's a sealed unit set into the rubber moulding then the wire goes down behind the under wing shield round the corner and up onto the top of the fuel tank where it plugs into the forward loom under the big round access to the pump.
You can check at those connections if the tank cap switch is working but from there on...........................................

[Tim1968]

Is the filler cap is ok, i'd remove wheel arch liner and check wire and connections for corrosion.

Is this a mk2 or mk3 C5?

Sept 2008 so mk3 i presume.

[Tim1968]

Just about all the diesels with particle filters have the same plug detect harness. Be aware that these are no longer available from Citroen now, so if it is your harness, it will need checking the wiring connections and repairing if necessary or a replacement if you can get it.

Hi Marc,

Gone through hoops here in Ireland trying to sort this. Had it checked and wiring is ok, cap is ok so looks like its the sensor itself. Living in the a*** hole of nowhere in Ireland not many options so it looks like its going to be a part from a breakers. My vin is VF7**************[VIN obfuscated, can be read by forum staff] would you be able to get the part number so I can go searching please.

Regards
Tim

[Gibbo2286]

I got a new one for my 06 estate I think from ebay.