You aren't going to like this job!
Here's a link to my old post when I did mine. I have become pretty good about pulling out the ABS Unit after three times, once was from using an USED pressure switch, and a bad Accumulator. For under $200, you can have both brand new. Give a hollar if you need help.
http://www.sccoa.com/forums/showthread.php?t=38267&page=1&pp=15
Also try this.....
http://www.35ththunderbirdregistry.org/Tips/ABS.htm
''''''''This is from an older post of mine'''''''''
__________________________________
This is the SAME pressure switch as used by Ford, but 1/3rd the price.
"GM Part #25530882 (Pressure Switch)
Paid $75.00 from
http://www.buy-gm-parts.com/
Shipping will run $12 - $25 depending on how fast you want it.
Price is now $83.00 and part number not found. Basically click on "OEM Catalog" choose "1988 Buick Reatta" and then in the Brakes" section choose "Anti Lock" then "Pressure Switch". OR just email them the part number direct. They shipped it out in two days to me, just UPS took forever.
Email Keith:
parts@crowncadillacolds.com or call Keith at 1-888-337-1094 ext-1127"
___________________________________