Reading and Clearing Diagnostic Trouble Codes

The Heating Ventilation and Air Conditioning (HVAC) programmer contains sophisticated self diagnostics that, when accessed with a Tech I scan tool, are designed to identify the source of any system malfunction as specifically as possible, including whether or not the malfunction is current or the non-current (history) type. When a fault is present the Vacuum Florescent (VF) display panel will flash.

Displaying and Clearing Diagnostic Trouble Codes

The only way to display diagnostic trouble codes (DTCs) is by using a Tech 1. There are no provisions for On-Board or "Hash" diagnostics.

The DTCs in the HVAC programmer are erased in one of two ways:

Tech 1 Method

Select F2 for diagnostic trouble codes. After DTCs have been viewed completely, Tech 1 will ask, "CLEAR DTCs"?; answer "YES." Tech 1 will then read "HISTORY DATA WILL BE LOST. CLEAR DTCs"? Answer "YES." and the DTCs will be cleared.

Ignition Cycle Default

If no diagnostic trouble code occurs for 50 drive cycles (a drive cycle occurs when the ignition is turned "ON") any existing history DTCs are cleared from the HVAC programmers memory.

NOTE: Be sure to verify proper system operation and absence of DTCs when the clearing procedure is completed.