General Description

There are four diagnostic "modes" or levels: LO, M1, M2, HI. Each level has a separate function:
LO Checks the ambient air temperature sensor, air mix door feedback, and air mix door travel.
M1 Checks the interior temperature sensor, a/c clutch status, and temperature lever potentiometer (heater only system).
M2 Makes the Air Control Module operate the air mix door through its entire travel range. This level has four sub-levels.
HI Checks the ambient air temperature and Interior air temperature sensor circuits. This level has two sub-levels.

Fault codes are displayed in modes LO and M1 only. Modes M2 and HI are for more in depth testing of some individual components.