Swapped all four wheels with another C5 and to speed the process jacked the back wheels under the towbar. During the process I raised the suspension for more clearance. After finishing the job and lowering the car the rear suspension remained fully extended and no amount of starting the engine and cycling the suspension up and down would budge it. Disconnected the battery and went away to sulk over a long cup of tea but to no avail. Driving round the block collecting strange looks and a sore back didn't help. Swapped sensors with the other C5 which had had the same treatment but wasn't affected didn't help either. Prized the arm off the sensor and locked the sensor with a 3/16" drill and cycled the suspension and the back came all the way down. There wasn't enough room to get under so I surreptitiously jacked the rear at the towbar enough to get under to reconnect the sensor, cleared everything away and.. all good.. as the aussies would say.
I assume the holes that the drill went thru put it in a null position.
I guess the moral of the story is too only do one wheel at a time.
A little long winded but hopefully it might help someone out.
C5 rear suspension locked up after wheels changed
Moderator: RichardW