[gmtech1]

Sounds to me like a both of you have either temp door actuators or temperature door problems. Not sure where the actuators are located on these cars, but you could remove the actuators and move the doors by hand to be sure they are ok. There may be codes stored in the bcm or hvac module to assist in diag. A basic code reader will probably not read these codes.

Looks like you can pull the glove box out to access the actuator, doesn't appear to be too tough. On a dual temp set up, there will be an actuator on both sides on the HVAC housing.