How to Retrieve a DTC (Without HDS) The audio-HVAC module has a self-diagnostic function for climate control. To run the self-diagnostic function, do the following: NOTE: Before troubleshooting the climate control system, refer to the multiplex integrated control system test mode A. Turn the ignition switch ON (II). Press the AUTO button and then the OFF button. Continue to hold both buttons down for 2 seconds. | Without Navigation System: With Navigation System: