I've got a (UK) 2005 Ford Focus C-Max zetec with electrical problems. It started with intermittent wipers, indicator lamps, central locking and interior lights either not working or coming on/sticking on even when switched off, and sometimes with the ignition off (which would drain the battery). All points to the GEM, but there is no sign of any corrosion or water ingress.
Now none of the functions controlled by the GEM work at all (instrument cluster and engine management are fine). I bought a second hand GEM (exact same model number) but it has made no difference.
I'm thinking must be an issue with the connectors to the GEM somewhere. The ends that plug into the GEM are all fine, but any advice as to where else I might try looking for corrosion or loose connections? It's not at all easy to trace where the cables go.