Displaying HVAC diagnostic '99

[Fireflynj]

Diagnostic Trouble Code (DTC) Displaying
The heater and the A/C programmer set the diagnostic trouble codes (DTC) for the air conditioning system. One of the following methods may display the DTC:

The Scan Tool Display DTC selection
The on-board method
Press and hold the OFF, AUTO and the RECIRC buttons for 1 second.
The DTCs will display for 2 seconds each, and then return to normal operation.



Try it, does this work?
it's from a '99 Buick Park Ave tech manual, for Automatic climate control, I'm trying to find out what is wrong with mine, it did not give me a code.