2004 206 1.6 HDi fuel filler cap sensor - how does it come off?

[MattBLancs]

Have error code for tank sensor fault (will look up the code shortly, have it written down)

Cap has two magnets present and correct.

Dug into right rear wheel arch to remove current sensor and check its wiring.

How does the sensor actually unclip from tank inlet?

Terrible image of filler neck end + sensor

Secondly, is there any specific resistance it should read if ok / dead?

Third and final question, is it a case of splicing the wiring as seems to be fed direct to a larger wiring plug - visible from under right rear passenger seat base tank access hole:

Have had a search of the forum but not found answers to all the above as yet (will keep digging!)

Thanks,
Matt

[CitroJim]

I'd like to think, given it only has two wires going to it, that it's simple contacts that are kept closed (or open) by the magnets...

If so, easy to test... Otherwise, and knowing how PSA love to make simple things complicated it may well be a Hall Sensor..

Wikipedia has a useful article on it and might help devise a test for it...

https://en.wikipedia.org/wiki/Hall_effect_sensor

[MattBLancs]

Thanks Jim,

Am sure I've read it's not so simple as a reed switch that the magnets pull open or closed, but can't find the source again. Will have a browse of the forum more generally looking at these tank cap sensors, with a bit of luck hopefully the method of operation remains the same across PSA!

[Gibbo2286]

Top end at the tank neck is just sitting in the rubber seal, no clips or screws, this is the test but it's foreign and quick.

[MattBLancs]

Top end at the tank neck is just sitting in the rubber seal, no clips or screws, this is the test but it's foreign and quick.

Perfect, thanks - will nip out in the dark after tea and have a play with the multi meter.

Will have to get a bit more forceful and see if can get sensor detached. I loosened plenty of dusty dry road muck to tumble down towards my eyes, but no movement of the sensor itself

[MattBLancs]

Video says cap off (no magnet) 14 ohms,
Cap on, magnet present 150 kOhms.

My readings:
Cap on= 4.8 Ohms
(Meter leads = 0.5 Ohms)
Cap off = 4.7 = effectively no change.

[MattBLancs]

Wiring looked ok, no obvious damage. Connection also looking ok too.

Magnets both present and correct.

Didn't bother in the dark yesterday, fire was roaring in the front room so the enthusiasm "melted away"

[CitroJim]

That's looking like a duff sensor Matt... One last thought and maybe a daft one (I'm good at those but in my professional life I was taught to go through every possibility, however unlikely it may seem)... Are the magnets themselves OK? Do they still be have as magnets in the presence of ferrous objects?

Also, take any other known good small magnet you may have - say one of those magnetic pickups for retrieving lost screws - and see how the sensor performs with that...