Mitsubishi Galant 3.0 v6 electrical problem 2003?

I am having an electrical problem with my wife's galant.Whenever she indicates left she has all sorts of problems,if the car is running with cruise control on and she then indicates it knocks cruise control off.When indicating and braking the brake light starts flashing and the flasher unit starts clicking twice as fast...release and it slows back down.The interior lights like radio and digital tachometer flash in rhythm to the indicators too.Is the problem a simple loose earth or is it an ecu problem.She has had an engine service light come on and a tcl warning light come on a few weeks after a service but these have dissapeared after disconnecting and reconnecting the battery.Any ideas where the relevant earth points are for this model,will i need to remove the dashboard,is it easy to get too, or is it an ecu problem and how much would one of those be.Any help with any of these questions would be appreciated.Thanks.