Help/advice Needed

Hi guys, messing aboot with the Tbird re-routing a standard cable for a sat nav, from an accessory plug up across underside of tank to the handle bars, followed the route of a previous one.
all seemed ok unplugged it from socket and went out to fuel the bike up and as I turned off my ignition the console lights are all flashing and flickering, ingnition back on all seems ok turned off again and all back flickering, rode home and now although illuminations have stopped I have an engine light on.
Checked the route of wire does not seem to be interfering with anything but i still have engine warning light on.
Question will this go off ? three cycles ?
For now I have disconnected the battery (who knows on some seems to clear some problems)
ANY OTHER IDEAS YOU LOT ??

PS - away at a rally tomorrow morning

 

accessory socket was just a standard plug in I normally use to blow up my air bed etc its wired direct to battery with an in-line fuse. (point taken re- piggy back to horn for future ref )