If you've got an MTC then 49 indicates an A/C control mode door input shorted to battery. If you've got the online FSM downloaded check out section 24 for the explanation of the Mode Door Actuator. Could be a wiring problem or the actuator itself...have you done any stereo or electrical work in that area?
I believe the mode door controls whether you get air to the floor vent or to the dash vents. Check to see if you get a switch from the floor to the dash when you change the control knobs to the appropriate vent. I doubt it will change or you get air coming out of both at the same time. My Body Diagnostic Procedures manual indicates these four causes:
Mode switch MUX circuit shorted to battery
Mode switch MUX circuit open
Manual HVAC head failure
It could also be a bad connection at the C1 connector at the MTC head or The C2(black) connector at the BCM. You could try reseating them before digging further. If you want I can scan the two pages from the diagnostics manual if you PM me an email address. It's too much work to scan, post to my web page and then link back here