Any thoughts on what would make cruise control quit while just cruising down the highway? Problem has gotten worse over the last couple of months to the point where sometimes I can't even set the cruise to start with. No apparent pattern to this and within any random amount of time it may/may not work again.

2000 s80 2.9 (non-turbo)

 

Does your check engine light come on? does you ABS light come on? Does your message area say "brake failure stop ASAP?

if so i'l guess it's your ABS module--same thing happened to me. I had the ABS fixed and all was well.

 

I had all the typical abs symptoms last fall and replaced the abs module - all was apparently fixed and no codes or anything showing up now.

 

You most likley have a vacuum leak in the line somewhere. Find the control unit and replace all the vacuum tubing. As the hole go bigger the problem got worse.