Toyota 97 Avalon ABS light

My Avalon (with traction control) had some ABS problems--worked fine most of the time, but had some mysterious failures in cold weather, mechanic thought there might be some moisture in the computer that freezes and causes some shorts. Anyway, I found a couple of used actuator units (new ones cost $1200-1400) that matched the part number and replaced it three times. None of the new units would ever work, the ABS and Trac lights were always on. The Trac light would flash 43, which my Haynes manual says is some basic malfuntion, but doesn't give any details. My last thought is to take it into the dealer. I thought I'd ask you if you had any info for me before I take it in. I've also got issues with an airbag light that comes on whenever I disconnect the battery (flashes 31) any help on that would also be great.
Thanks. Sorry I can't donate more than I did.
Josh

150,000 miles
XLS
North American made