Audi A6 C5 Air Conditioner Output Diagnostic Test Mode (DTM)

Initiating output DTM
- Star engine (vehicles up to model year 2001).
- Switch ignition on or start engine (vehicles from model year 2002).
Notes: The engine should not be running, if the actuation of "A/C Compressor Regulator Valve -N280-" or "A/C clutch -N25-" is being checked on vehicles from model year 2002. With engine running the A/C Control Head -E87- does not actuate these actuators, but starts the output DTM with Fresh Air Blower -V2-.
The engine must be running, if the activation of Coolant FC (Fan Control) Control Module -J293- on vehicles from model year 2002 is to be checked. Depending on engine type, the A/C Control Head - E87- sends the request to switch on the coolant fan directly to the Engine Control Module (ECM), the Coolant FC (Fan Control) Control Module -J293 or to one of the respective coolant fan relays. Depending on the version e.g. the Engine Control Module switches the coolant fan on, but only with the engine running.
Electrical Wiring Diagrams, Troubleshooting & Component Locations
- Press AUTO button to switch compressor on.
- Open instrument panel vents.
- Set air distribution to instrument panel vents.
- Connect VAG 1551 Scan Tool (ST),Press buttons -0-and -8- to insert "AC/Heating Electronics" address word 08 and advance program until "Select function XX" appears on display Page 01-11 .
- Switch printer on via the PRINT button (indicator lamp in button lights up).
- Check DTC memory.
Indicated on display (function selection):
- Press buttons -0- and -3- to select "output Diagnostic Test Mode" function 03.
Indicated on display:
- Press -Q- button to confirm input.
Indicated on display:
- The button is used to advance through the program sequence.
Notes: Pressing the C-button can terminate output DTM. When output DTM is completed, check DTC memory.

source pdf: http://www.vaglinks.com/Docs/Audi/C5/Audi_A6_C5_AirConditioner_OutputDiagnosticTesting.pdf