I have a 1993 xj6. abs light always comes on when I first start
it. I counted, it flashes 6 times. sometimes will remain lit, other
times will go out, but always comes back on and remains on when
driving. I just had my 1st experience driving this car in the snow
the other day, and I can only assume the breaks are not working
right because it was a terribly frighteneing experience! front
wheels kept locking up on me and rear whells wanted to keep pushing
the car causing me to slide quite a bit. leaving off the break
helped as it would resume course, but I don't think the should be
locking like that right?

 

I've got a 93 xj6 as well and had similar problem a few years ago when I bought it. The abs light would sometimes come on and off but it didnt effect the way it drove the few months I had to use it in the snow. Doesnt help that they're RWD too!! But I did end up replacing my front right abs sensor for about 80 bucks. See what you're Jag mechanic reccommends but it's usually just a lot of brake dust accumulating over the years that screws around with the sensors. My abs light has been on for almost 2 years and hasnt bothered the way the car drives at all. I bet I didnt even need to replace the sensor I bought!