you mean the can gateway, that is very easy to test, the test will show if can high or can low has a fault, when i first read this i thought of the bonnet catch but that wouldnt explain the indicators not working, i wouldnt have thought the ABS would play up the wipers tho, maybe wrong tho, did they code read your car? if you need more info on testing the canbus i will explain it as easy as poss and then explain how to test it if thats any help mate