I was able to diagnos the code myself on my 96 caravan 3.3L by doing the following.
Turn the key to all the way on position [but not starting the vehicle] then back to the off position. Do this twice then turn the key to the All The Way ON Position [but not starting the vehicle] and leave it there. BE SUCH AND HAVE A PEN AND PAD READY. The check engine light would give a series flashes then pause......repeat for a few more times. Write down the number of times it flash in between each pause.
Example: flash flash -PAUSE- flash flash flash flash -PAUSE- flash flash flash -STOP. These flash CODE are 2-4-3. When you obtain this code, post it and I would tell you what the code mean/what area is defective. It works for the 97 Caravan but I dont know if the 02 does the same; It dont cost anything, and its worth a try.
BE SURE TO POST THE CODES SO I CAN GET BACK TO YOU. POST A MESSAGE EVEN IF IT DOES NOT WORK.