Some of these vehicles, you can put into diagnostic mode without a scanner. I not sure with your model year. It can't hurt to try.
With all fuses plugged in and the battery charged, cycle the key between the off and acc position three times, the third time, leave it in the acc position. If it will go into diagnostic mode, the headlites and tail lites should flash and the horn will honk. Anything? If it goes into diagnostic mode, you can turn the key off, to stop the lites from flashing, but it still should be in diagnostic mode. You can open the doors, one at a time. Every time the door switch is activated, the horn should honk. When you open and when you close it. Between the opening and closing, you may have to wait thirty sceonds. The point being, if the horn doesn't honk, there is something wrong with the switch or wiring circuit. I know you replaced a door switch, but there is one for every door, probably one for the liftgate as well, I don't know how many you have. I don't think the switches would be hard to test To take it out of diagnostic mode, you turn the key to the run position.
You may not be able to put it into diagnostic mode with out a scanner. I'm not sure.
I know you wish somebody could tell you the problem without all this testing, but, I don't think that is going to happen.
Tuesday, February 27th, 2007 AT 1:28 PM