GM Service Manual Online
For 1990-2009 cars only

HVAC Control Module

Scan Tool Parameter

Data List

Units Displayed

Typical Data Value

Ignition ON/Engine OFF

Rear Defrost Switch

Input/Output

On/Off

Off

Liftgate Module (LGM)

Scan Tool Parameter

Data List

Units Displayed

Typical Data Value

Ignition ON/Engine OFF

Defog Relay Voltage

Data

Volts

12.5

Rear Defog Requested

Data

Yes/No

No