93 saturn SL2 ABS woes

I have an annoying abs problem... My abs passes initial startup tests,
but as soon as I get over 15MPH the abs light comes on..Here are a few
things that I have noticed:


1. The brakes do make the acuatating clunk noise when i first
accelerate

2. I have cleaned all 4 wire connections to the sensors


3. have replaced the front wheel sensors with brand new ones; so maybe
one of the rear sensors is bad?? (I hope not)I had no front wheel
sensors for about a week, and the abs light didn't light didn't turn on
until about 35mph, but after replacing the two front sensors the light
clicks on immediatley after about 15mph..

4. i haven't noticed any flucuations in power, I have replaced the
battery with a brand new one, battery connections are all clean....

5. i tried disconnecting the battery , and the mini-fuses/maxifuses in
attempt to reset the diagnostic computer.....



6. i have noticed that sometimes taking the car through the car wash,
will temporairly eliminate the problem.....seems weird to me


any ideas are appreciated......


as a a last resort,anyone have any good recommendations for an obd
scanner for this car??/

THANKS,

CHAD