Ten year old post, yet still helping folks out! Thanks! Fixed it on my lunch break and had cruise control on the way home!!!
Originally Posted by bluesubie
Hey, that happened to my OBS. Yes, it could be the same problem with your Impreza.
Take a look at the clutch pedal. About halfway up you'll find the plug thingy. I believe it's white. If it's broken or missing, your cruise won't engage because of the switch there. If you need a new one, it's only about $2 or $3.
Other possibilites are loose vacuum hose or bad fuse.