C5 Mk1 Rear Parking Buzzer / Speaker Fixed

[aspire_helen]

I noticed I was getting no sound from the rear parking sensors, nor was I getting any warning they were not working. Reverse lights and dipping mirror still worked so gearbox switch was OK. Lexia3 did in fact record a permanent fault "rear parking speaker open circuit or earthed" - quite specific! I was impressed that the car clearly measures the speaker circuit impedance but cannot determine whether it is open circuit (broken wire etc) or closed circuit (earthed).
Of course with no speaker, how would you find it? Luckily, last month I recovered the Cpillar trims and discovered the speaker screwed to the rear of the left trim. Who knew? I suppose the panel gives the speaker a bit more volume.
Sure enough, it was open circuit, but no visible damage. The black plastic housing contains a standard 36mm mylar passive speaker rated at 0.2W 50ohm - the kind used for headphones and telephone handset earpieces. However, its terminals are soldered and moulded into the housing. I found the genuine Citroen part 6590A6 for sale in Slovakia and Russia at £45 to £50 !! Used items on Ebay for £10+. Generic ones are available from China for under £5, but the connector may not match. However, I found on Ebay a pair of similar speaker inserts (50ohm, 0.5W) advertised as a pair for head phones - £3.99 the pair delivered. The speaker slots nicely into the housing (with top prized off) except for the terminals. By pure coincidence, the speakers terminals were sized and spaced almost identical to the connector pins of the original, so I pulled out the original pins, fettled the moulding and lined up the speakers terminals to align with the car's connector, and it worked perfectly. I did NOT refix it to the Cpillar trim, but under the rear left seatbelt spool trim for easier access.
Regarding the Cpillar trims - when removing them, the "Airbag" badge MUST be prised out first. It is actually a plug which retains the trim. It is very reluctant, and take care not to damage the fabric - patience!! Also, prise it out near its centre, and not the ends. To release the other trim clips, simply pull the trim panel firmly and squarely away, remembering the speaker inside the left one is attached.

[jamescarruthers]

Nice fix! Thanks for sharing for others to beniefit

[dave21120]

Thank you for your post - great timing as I'm just upgrading my vtr to have parking sensors from an exclusive, and was scratching my head as to where the speaker should be.

Now I know

[aspire_helen]

Does anyone know whether Lexia3 can be used to adjust the detection sensitivity of parking sensors, notably to disable the inner pair so they dont trigger on a towball? I know the Citroen towball includes a switch to automatically disable the system when the towbar is fitted, or is it when the towbar electrics are connected?

Re retrofitting Citroen parking sensors. Below is a link to a guy who has retrofitted several factory systems onto his C4 with extremely good directions. This may help.
https://minotaurus.pl/en/how-to-fit-fac ... itroen-c4/

[GiveMeABreak]

No it can't. The system is an all or nothing by design.

Citroen's wiring kits with the proper Trailer Fuse Box are designed to work with the vehicle to provide a special ESP programme when towing is detected and also to deactivate the rear parking assistance when towing. That's why they cost a bit more, but they provide these safety features.

Lexia cannot deactivate individual sensors or adjust them - they are pre-defined units. You will need to switch the system off from the Centre Console manually.

[aspire_helen]

Thanks Marc
There is no facility to turn them off. However, when I get around to it I will re-locate the inner pair further apart, and fill the holes they leave with some spare, unconnected sensors - just for looks. I do not mind them triggering on a trailer, but it annoys me that they trigger on the towball, especially with a cycle rack fitted.