I've been looking for this for years and stumbled upon it. It comes from the manual for a Baum Tools CS1000 scanner which I downloaded a year ago. I don't own the scanner, but since the manual gives the meaning of all the DTC's it is very useful. This post is just for the ACC unit.

Reading Actual Values
1. Ignition to Position 2 with engine off or on.
2. Press the REST button and within 1 second press blower speed button 4.
3. The temperature window will alternately display the test step number (ex. "02 = in-car temp.) and the actual value.
4. Use the "F" and "C" keys to navigate to the different tests.

Test 02 = In-Car Temperature Sensor
Test 04 = Outside Temperature Sensor
Test 06 = Evaporator Temperatrue Sensor
Test 08 = Heater Core Temperature Sensor
Test 12 = Engine Coolant Temperature Sensor
Test 14 = Temperature Selector Wheel Setting
Test 18 = Vehicle Speed Signal (km/h)
Test 20 = Soft Top OPEN ("u") or CLOSED ("o")
Test 22 = Power Supply Voltage
Test 83 = Not Used
Test 84 = Blower Motor Voltage

To exit this test mode press "0".

Retrieving Stored Diagnostic Codes
1. Turn temperature selector wheel into the white area.
2. Ignition to Position 2 with engine off or on.
3. Within the next 10 seconds, press the "F", "RECIRCULATE AIR" and "REST" buttons simultaneously for 2 to 4 seconds.
4. The display will show the permanent DTC's stored. Press the "RECIRCULATE AIR" button after each is displayed until the display reads "END".
5. Press "RECIRCULATE AIR" button again and the intermittent DTC's will be shown. A square is shown after each of these DTC's to indicate it is intermittent. Press the "RECIRCULATE AIR" button again to see the next intermittent DTC and continue until "END" is shown.
6. To erase the DTC's: switch ignition from off to Position 2 and within 10 seconds press "RECIRCULATE AIR", "REST" and "UP" buttons simultaneously until "---" is displayed.

DTC codes: I will email a list of them to you if you like. There are too many to list here, but know that "1" = no DTC's in memory.