Diagnostic Starting Point - HVAC System - Manual

Begin the system diagnosis with A Diagnostic System Check. The Diagnostic System Check will provide the following information:
^ The identification of the control module(s) that command the system.
^ The ability of the control module(s) to communicate through the serial data circuit.
^ The identification of any stored Diagnostic Trouble Codes (DTCs) and their status.
The use of the Diagnostic System Check will identity the correct procedure for diagnosing the system and where the procedure is located.