My problem was the brake deactivation switch too. Have you had any work done on the car lately where someone would have been in drivers footwell area? Anyway, to get at the pedal switches that interact with the cruise control, you need to remove the panel underneath the steering wheel. I think the bolts are all 6 or 8 mm if I remember correctly. You will also need to get the hood release out of the way, there's a big nut on the back and a crescent wrench will loosen it some (don't remember size, might be 3/4 or something) then you pull it down out of the way; the release cable is just in a groove and the nut holds it in place. You would also need to pop the OBD scan port through the panel for the panel to come free, I think this is easiest if you get the panel loose and then use a small screwdriver or something to wedge it through the gap, look at it closely and be careful with it as it could be an expensive mistake, but it pops through pretty easily. There will be a small panel covering the OBD port and it just pops out with a finger pull at the bottom.
Once the panel is free you can get down in the footwell and examine the pedal assembly and switches. There will be 3 switches in front of the top of the pedals. The brake deactivation switch is the green one on top, stop lamp switch is grey, and clutch position switch is red. They all work the same way, they have spring loaded plungers that either open or close circuits when they extend. In the case of the brake deactivation switch, you hit the brake, the pedal arm moves away from the plunger, the plunger moves out and the circuit opens, deactivating the cruise control.
Odds are very good that green switch is faulty. The BPP switch has a ratcheting mechanism that only goes one way, so for instance, if you were to intentionally pull up on the brake pedal the plunger would go further into the switch and if you then let go of the pedal the plunger might not extend far enough back out to contact the pedal arm, and the circuit would stay open and disable the cruise control. You can test the switch by bypassing the plunger mechanism and using a little jumper wire to complete the circuit. To remove the green brake switch you rotate counter-clockwise and some tabs line up with slots and then you can pull the switch from the pedal assembly; it will be the plunger mechanism and a little wiring harness deal it mates with. You separate the two by taking a small pick or something and pulling out the square little brass tab(that's a misleading description, but you'll recognize it when you see it) it just pulls straight out and then the plunger mechanism will be free from the wiring.
I don't remember now how many wires are involved. If there are only two you can just find the corresponding connections in the bottom of the wiring harness and bridge the gap with a small (thin) jumper wire (just a small wire with stripped, nicely twisted ends like a spliff). This closes the circuit and fools the CC system into thinking that the brake pedal is in its normal position. You could then run the self diagnostic again, and if it passes you will know that the problem was the plunger switch. I'm going to try to check some schematics tomorrow and see if I can identify exactly where the jumper wire needs to go. Incidentally, you could keep the jumper wire in and leave the plunger mechanism out altogether, but then you wouldn't be able to shut off the cruise control with the brake and that's a little dangerous.
The switch was like $25 from a local dealership, so you could just buy the switch and put it in. Also, if the only thing you mess with is that green brake switch, it won't affect the car at all to leave it disconnected while you figure it out; that switch only interacts with the CC system and that's already broken, so you can't harm it anymore by leaving it disconnected.
To install the new switch, just plug the switch and harness back together, and push the square metal tab back into place. Then you have to depress the brake pedal, line up the switch correctly so it slots back in, and then turn it back clockwise until it stops. Be careful not to depress the plunger when putting the switch back in, it could effectively ruin it since it only ratchets in and doesn't come back out all the way. Then you release the brake pedal and the plunger ratchets to the correct position and that's it. Set aside plenty of time and make sure you have a good light source so you can see what's going on around the pedals.
Just realized I wrote an entire novel about a cruise control brake pedal position switch.
Last edited by 6SPD_soul; 05-17-2011 at 05:14 PM.