Could be a blender door actuator.
These 4 doors are each driven by a DC motor with a feedback wire to tell the computer which position each door is in. Think of these systems like the throttle position sensor in your EFI system, as they work on the same principle.
Now, with the proper knowledge of this system, try diagnosing it yourself. To get an accurate diagnosis, TESTS 1 and 2 need to be done right after each other.
TEST 1: The head unit has a self-test feature that you can use to diagnose just about any problem with the ATC system. Put the ignition key to the "on" position and set the head unit to 90 degrees and OFF. Wait 40 seconds. If the display begins to flash then you have a wiring problem with the blend actuator, a bad actuator, or a bad head unit. If the LED light begins to flash then there is one or more of the problems previously mentioned.
Address the problems or continue with the test. After no flashing occurs, set the head unit to 60 degrees and DEF. Again wait 40 seconds and look for a flashing display or LED lights. If there is no flashing, there is no problem with the actuator or circuitry.
TEST 2: Push the OFF and DEFROST buttons at the same time. Within 2 seconds, push the AUTO button. If an 88 is displayed, everything supposedly is fine according to the head unit. If you look below, the shop manual also says the number 9 is fine too. Take it for what is worth, I guess. Any other numbers show a problem with the ATC system. Now is the time to write down the number of numbers displayed on the ATC head unit. When you are done with the codes press the COOLER button to put the ATC back into regular mode. The temperature control will now be one degree cooler than what you had set it before running the test. Cool, huh? Now turn off the ignition and figure out how to fix your problem.
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The Codes
1, Blend Actuator out of position, display flashes
2, Mode Actuator out of position, LED flashes
3, PANEL/DEF Actuator is out of position, LED flashes
4, Fresh Air (Vent) Actuator is out of position, display flashes
1, 5 Blend Actuator output shorted, display flashes
2, 6 Mode Actuator output shorted, LED flashes
3, 7 PANEL/DEF Actuator output shorted, LED flashes
4, 8 Fresh Air Actuator output shorted, LED flashes
9, No failures found
10,11 A/C clutch is either always on or always off (you can figure this out easily)
12, System stays in full heat (In car temp above 60° for this test to be valid)
13, System stays in full a/c
14, Blower stays at full speed
15, Blower never runs
I'll test it out this week.
