sorry to chip in with what could be a silly question as im not up to speed on 400s !!
would a 95 400 be obd2 or would it be the paper clip method to extract codes that i have read about in some sections ? if paper clip type should be easy enough to grab the fault codes and narrow down the problem no ? ,,,,,,,,,,, sorry if wildly wrong just read and posted didnt go back and research extensively