thanks for everyones help. Aaron, i tried the things you suggested. the results are as follows:
1. when i sit in the car with the engine off (has not run for over a day) and i lock the drivers door, the paasenger door remains unlocked.
2. i then started the engine and waited a couple of minutes and then locked the drivers door, the passenger door remained unlocked.
3. i then drove for 5 minutes with the drivers door locked, the passenger door remained unlocked. when i drove for 5 minutes with the drivers door unlocked, and then locked the drivers door the passenger door would then lock.
4. after driving for 5 minutes, with the engine just shut off, using the key the drivers door, passenger door, and truck locked. the fuel door remained unlock.

i just bought a mity vacumn tester, though i haven't learned to use it yet. what does all this mean and what should i try next. thanks again for the help.