On day of purchase Comms 2000 unit failed leaving no indicators.
After a week realised the Trafficmaster wasn't working correctly, dealer tried parts from service managers car to detect fault eventually waited 4 months for new unit. At least dealer arranged full 12 month licence.
After 3 months Comms 2000 unit failed again.
Interior lights come on in heavy rain, no fault found, but suspect water ingress in electrics.
Wheels replaced on a recall because they crack, apparently they are alloy, but look like black painted steel rims.
Air doser unit leaked oil, replaced twice and still leaking at disposal.
At 63000 most worrying the suspension developed a mind of its own. Setting changed every time engine switched on varying from very soft to very hard. Green indicator never altered and dealer said no fault codes found although after test drives they checked it out 3 times.
Audio controls on steering column stopped working and car went into permanent 'Eco Mode', dealer said no fault codes found (see above), but there obviously was so system remapped. TIP!!, if this happens to you disconnect battery for 30 seconds and reconnect, it worked on mine at leasst a further 10 times.
Doors started to stick unless pushed open from inside.
Radio interference on AM band from engine, rev related.
Nearside front window went up and down on its own after my wife and I both tried to lower it at the same time. Answer, we raised it both at the same time.
Like all C5's, headlamps flickered due to multiplex wiring system.
A spacious car spoilt by too much unproven or should it be unnecessary technology.
The proven parts i.e. engine, gearbox never a problem and in it's earlier days was a joy to drive, that joy went when suspension started to play up.
No problems with trim or bodywork.
Poor dealer support and Citroen parts availability is a problem in general.