GM Service Manual Online
For 1990-2009 cars only
Table 1: Heating and Air Conditioning
Table 2: PCM
Table 3: BCM

Use the Scan Tool Data Display Values and Definitions in order to assist in diagnosing the HVAC control module concerns. Compare the vehicles actual scan tool data with the typical data display value table information. Use the data information in order to aid in understanding the nature of the concern when the vehicle does not match with the typical data display values.

The scan tool data values were taken from a known good vehicle under the following conditions:

    • The ignition switch is in the ON position.
    • The engine is running at idle.
    • The vehicle is in PARK.
    • The doors are closed.
    • The windows are closed.
    • The A/C is ON.
    • The ambient air temperatures are at 22-27°C (70-80°F).

Heating and Air Conditioning

Scan Tool Parameter

Data List

Units Displayed

Typical Data Value

Operating Conditions: Engine idling, A/C ON, ambient air temperature between 22-27°C (70-80°F)

A/C LED

Module and Display Data

On/Off

Varies

A/C Request

HVAC System Data, Module and Display Data

Yes/No

Varies

A/C Switch

Module and Display Data

Active/Inactive

Varies

Ambient Air Temp. Sensor

HVAC System Data, Sensor Data, Actuator Data

°C/°F

Varies

Auto Mode

HVAC and System Data

On/Off

Varies

Battery Voltage Signal

HVAC and System Data

Volts

Varies

Blower Motor Speed Command

HVAC System Data

%

Varies

ECT

HVAC and System Data

°C/°F

Varies

Engine speed RPM

HVAC and System Data

RPM

Varies

Inside Air Temp. Sensor

HVAC System Data, Sensor Data, Actuator Data

°C/°F

Varies

Lower Duct Air Temp. Sensor

Sensor Data

0-255

Varies

Mode Dr. Motor Command

Actuator Data

0-255

Varies

Mode Dr. Position

Actuator Data

0-255

Varies

Mode Status

HVAC System Data

Def/Defog/Panel/Bi-level/Floor/ Auto

Varies

Outside Air LED

Module and Display Data

On/Off

Varies

Outside Air Mode Switch

Module and Display Data

On/Off

Varies

Recirculation Dr. Motor Command

Actuator Data

0-255

Varies

Recirculation Dr. Position

Actuator Data

0-255

Varies

Recirculation LED

Module and Display Data

On/Off

Varies

Recirculation Switch

Module and Display Data

Active/Inactive

Varies

Sunload Sensor

Sensor Data

LUX Counts

Varies

Temp. Dr. Motor Command

Actuator Data

0-255

Varies

Temp. Dr. Position

Actuator Data

0-255

Varies

Temp. Down Switch

Module and Display Data

Active/Inactive

Varies

Temp. Up Switch

Module and Display Data

Active/Inactive

Varies

Upper Duct Air Temp. Sensor

Sensor Data

0-255

Varies

Vehicle Speed

HVAC and System Data

mph/km/h

mph

PCM

Scan Tool Parameter

Data List

Units Displayed

Typical Data Value

Operating Conditions: Engine idling, A/C ON, ambient air temperature between 22-27°C (70-80°F)

A/C Disengage Reason

Engine Data

None, System Voltage, WOT, CKP Learn Active, Engine Run Time, Coolant Hot, Anti Stall, A/C Pressure, Engine Speed, Trans Engine Spd, A/C Press Sensor, Low Voltage, High Voltage, Outside Air Temp, A/C Switched Off

None

A/C Pressure Disable

Engine Data

Yes/No

No

A/C High Side Pressure Sensor

LX9 / 3.5L only

Engine Data

kPa/psi

Varies

A/C High Side Pressure Sensor

LX9 / 3.5L only

Engine Data

Volts

Varies

A/C Off for WOT

Engine Data

Yes/No

Varies

A/C Relay Circuit History

Engine Data

OK/Open/Short

OK

A/C Relay Circuit Status

Engine Data

OK/Fault

OK

A/C Relay Command

Engine Data

Yes/No

Varies

A/C Request Signal

Engine Data

Yes/No

Varies

FC Relay 1 Command

LX9 / 3.5L only

Engine Data

On/Off

Varies

FC Relay 2 and 3 Command

LX9 / 3.5L only

Engine Data

On/Off

Varies

ECT Sensor

Engine Data

°C/°F

Varies

Ignition 1 Signal

Engine Data

Volts

Varies

BCM

Scan Tool Parameter

Data List

Units Displayed

Typical Data Value

Operating Conditions: Engine idling, A/C ON, ambient air temperature between 22-27°C (70-80°F)

A/C Request Switch

Inputs

On/Off

Varies