Scan Tool Testing and Procedures

Diagnosis for this system is based on Diagnostic Trouble Codes (DTCs) stored in the Heater/Vent/Air Conditioning (HVAC) Control Head. When a DTC has been stored the MODE Indicator (LED) of the current mode will flash. Three dashes will be displayed on the HVAC Control Head if the Programmer fails.

TECH 1 DIAGNOSIS
Vehicle Preparation
^ Connect a jumper from the HVAC Control Head Connector, terminal "4" or terminal "5", to the Data Link Connector (DLC) Connector, terminal "14." Insert the jumper through the back (wire entry side) of each connector.
^ Install the Tech 1 using the Body Systems Cartridge. When the Tech 1 asks for the model, key in 1990 (not 1995).
^ Proceed with climate control diagnosis


IMPORTANT: To prevent future data line communication problems, remove the jumper wire after diagnosis.