I had this happen in my old pickup. Turned out to be that the wire harness that goes to the vacuum switching valve grounded out. Burned up the end of the harness to it. No clue how/why that happened, but it was the same symptoms you're talking about. I ended up having to just keep trying fuses since I was stuck on the side of the road. Finally got it home ... I guess the wire moved enough to quit grounding out. Ever since then I kept a box full of fuses, lol.

Richard <img src="/forums/images/graemlins/patriot.gif" alt="" />

Had an 89 Isuzu Pickup
Had a 94 Mitsubishi Eclipse
84 Honda XL185S
Had an 89 Isuzu Trooper w/ 3.4 V6
01 Toyota Tundra SR5 V8 4Door Access Cab
http://community.webshots.com/user/rsayloriii