Here's a quick fix you can try. It recalibrates the ventilation control system:
"Start the van and turn on the blower. Simultaneously push the top and bottom wiper buttons on the left side of the ventilation control panel for 5 seconds. All the lights on the panel will light up. Then two lights on the left side will alternately flash for about two minutes and you'll hear the ventilation modes cycle. When just the top light on the left side slowly flashes push that button and you're done. All lights should be out and you should be back to normal. Restart the van a few times and make sure. This is the ventilation control/AC cool down calibration test and it resets the ventilation system computer."
If that doesn't work for your 02 try one of these:
http://www.allpar.com/fix/codes-climate.html
If this doesn't fix it you probably have a bad blend or mode door actuator, ventilation control panel (computer is in it), or wiring between them.