To start with -if you have got your handbook or any other info handy - check what other circuits are on the same fuse and check these are not faulty/are all working- sometimes a fog lamp for example may be on the same circuit and this may have blown. It may be difficult if the fuse is blown but replace it and try these other items and see if it blows (without starting the car or selecting reverse) Not an expert on C2s but have come across similair on other makes. Just a note of caution - some manufacturers dont list every ancillary that may be attributed to a particular fuse!!!!