IIC bus error (Machine failure)

[talcomovas]

I cleared the RAM, and configured the machine, but after the initializing process, it displays an "IIC Bus Error" message, I entered the self test menu and at the IIC driver check option says "BD button U1 error". I tried changing the masterboard for one working in another machine and same thing happens. Then, I changed the whole button driver board (the one at the door) and the error apears again. Also, I replaced the harness which connects between the backplane and the button driver board, and nothing!. I checked all buttons for any wrong connection and saw no problems. I've cleared the RAM hundreds of times and configured the machine in many different ways and same results. So if anybody has struggled with this problem please help me! (The only thing I haven't done is burning other eproms from a machine in operation, and it was because I don't have other machine with the same game, the game is Sign of the Zodiac).

Thanks people