GM Service Manual Online
For 1990-2009 cars only
Table 1: HVAC Control Module Scan Tool Data Parameters
Table 2: HVAC Control Module Scan Tool Output Controls

HVAC Control Module Scan Tool Data Parameters

Parameter

System State

Expected Value

Description

Operating Conditions: Engine ON

A/C Head Pressure

--

Normal

The scan tool displays Normal or Out of Range. This is the state of the A/C head pressure.

A/C LED

--

Off

The scan tool displays On or Off. This is the state of the air conditioning indicator.

AC Permission

--

Granted

The scan tool displays Granted or Withheld.

A/C Request

--

No

The scan tool displays Yes or No. Yes is displayed if the air conditioning is requested.

A/C Switch

--

Inactive

The scan tool displays Active or Inactive. This is the state of the A/C switch.

Ambient Air Temperature

--

Normal

The scan tool displays Normal or Out of Range. This is the state of the ambient air temperature.

Air Inlet Dr Actual

--

Varies

This displays Counts. This is the current numeric value of the air inlet door as monitored by the HVAC module.

Air Inlet Dr Commanded

--

Varies

This displays Counts. This is the numeric value of the air inlet door as commanded by the HVAC module.

Air Inlet Motor Drive

--

Varies

The scan tool displays Stop, Ambient Air, Increase, Recirculate or Decrease. This is the state of the air inlet motor.

Auto Switch

--

Inactive

The scan tool displays Active or Inactive. This is the state of the auto switch.

Aux. Blower Motor PWM

--

Varies

This displays percent. This is the percentage of power supplied to the auxiliary blower motor.

Aux. Mode Door Actual

--

Varies

This displays Counts. This is the current numeric value of the auxiliary mode door as monitored by the HVAC module.

Aux. Inside Air Temp

--

Varies

This displays °C (°F). This is the current temperature inside the auxiliary area.

Aux. Lower Duct Temp. Sensor-Actual

--

Varies

This displays °C (°F). This is the current temperature inside the lower duct area.

Aux. Lower Duct Temp. Sensor-Desired

--

Varies

This displays °C (°F). This is the desired temperature inside the lower duct area.

Aux. Mode Door Commanded

--

Varies

This displays Counts. This is the numeric value of the auxiliary mode door as commanded by the HVAC module.

Aux. Temp. Dr. Motor Command

--

Varies

This displays Counts. This is the numeric value of the auxiliary temperature door motor as commanded by the HVAC module.

Aux. Temp. Dr. Position

--

Varies

This displays Counts. This is the numeric value of the auxiliary temperature door position as monitored by the HVAC module.

Aux. Upper Duct Temp. Sensor-Actual

--

Varies

This displays °C (°F). This is the actual temperature inside the upper duct area.

Aux. Upper Duct Temp. Sensor-Desired

--

Varies

This displays °C (°F). This is the desired temperature inside the upper duct area.

Battery Voltage

--

Normal

The scan tool displays Normal or Out of Range. This is the state of the system voltage.

Battery Voltage Signal

--

Varies

This displays Volts. This is the battery voltage signal supplied to the HVAC module.

Blower Motor Speed Command

--

Varies

This displays percent. This is the percentage of power supplied to the blower motor.

Blower Speed

--

Off

The scan tool displays Normal or Off. This is the state of the blower motor speed.

Coolant Temperature

--

Varies

This displays °C (°F). This is the current temperature of the engine coolant.

Engine Coolant Temp

--

Normal

The scan tool displays Normal or Out of Range. This is the state of the engine coolant temperature.

Engine Running

--

Yes

The scan tool displays Yes or No. Yes is displayed if the engine is running.

Fan Down Button

--

Inactive

The scan tool displays Active or Inactive. This is the state of the fan down switch.

Fan Up Button

--

Inactive

The scan tool displays Active or Inactive. This is the state of the fan up switch.

Front Defrost LED

--

Off

The scan tool displays On or Off. This is the state of the front defrost indicator.

Front Defrost Switch

--

Inactive

The scan tool displays Active or Inactive. This is the state of the front defrost switch.

Ign. Cycles Since last DTC

--

Varies

This displays a numeric value. This is the number of ignition cycles since the last HVAC module DTC.

Inside Air Temp. Sensor

--

Varies

This displays °C (°F). This is the current temperature of the vehicle interior.

Left Sunload Sensor

--

Varies

This displays Counts. This is an approximate value at the left sunload sensor.

Left Temp Dr Actual

--

Varies

This displays Counts. This is the current numeric value of the driver temperature door as monitored by the HVAC module.

Left Temp. Dr. Commanded

--

Varies

This displays Counts. This is the numeric value of the driver temperature door as commanded by the HVAC module.

LH AC Duct Actual

--

Varies

This displays °C (°F). This is the current temperature of the driver side duct area.

LH AC Duct Desired

--

Varies

This displays °C (°F). This is the desired temperature of the driver side duct area.

LH Heater Duct Actual

--

Varies

This displays °C (°F). This is the current temperature of the driver side duct area.

LH Heater Duct Desired

--

Varies

This displays °C (°F). This is the desired temperature of the driver side duct area.

Low Pressure Switch

--

Closed

The scan tool displays Open or Closed. This is the state of the low pressure switch.

Mode Door Actual

--

Varies

This displays Counts. This is the current numeric value of the mode door as monitored by the HVAC module.

Mode Down Switch

--

Inactive

The scan tool displays Active or Inactive. This is the state of the mode down switch.

Mode Dr. Motor Command

--

Varies

This displays Counts. This is the numeric value of the mode door as commanded by the HVAC module.

Mode Select Position

--

Off

The scan tool displays Off, Auto, Defrost, Heater, Htr./Def., Bi-Level or Panel. This is the current position of the HVAC mode select.

Mode Switch Pos.

--

Varies

The scan tool displays Invalid, Auto, Panel, Bi-Level, Heater, Htr./Def. or Defrost. This is the state of the HVAC mode switch.

Mode Up Switch

--

Inactive

The scan tool displays Active or Inactive. This is the state of the mode up switch.

On/Off Switch

--

Inactive

The scan tool displays Active or Inactive. This is the state of the on/off switch.

Outside Air Temp. Filtered

--

Varies

This displays °C (°F). This is the filtered value of the outside air temperature.

Outside Air Temp. Raw

--

Varies

This displays °C (°F). This is the raw value of the outside air temperature.

Rear Defrost LED

--

Off

The scan tool displays On or Off. This is the state of the rear defrost indicator.

Rear Defrost State

--

Off

The scan tool displays On or Off. This is the state of the rear defrost system.

Rear Defrost Switch

--

Inactive

The scan tool displays Active or Inactive. This is the state of the rear defrost switch.

Recirculation LED

--

Off

The scan tool displays On or Off. This is the state of the recirculation indicator.

Recirculation Switch

--

Inactive

The scan tool displays On or Off. This is the state of the recirculation switch.

RH AC Duct Actual

--

Varies

This displays °C (°F). This is the current temperature of the passenger side duct area.

RH AC Duct Desired

--

Varies

This displays °C (°F). This is the desired temperature of the passenger side duct area.

RH Heater Duct Actual

--

Varies

This displays °C (°F). This is the current temperature of the passenger side duct area.

RH Heater Duct Desired

--

Varies

This displays °C (°F). This is the desired temperature of the passenger side duct area.

Right Sunload Sensor

--

Varies

This displays Counts. This is an approximate value at the right sunload sensor.

Right Temp Dr Actual

--

Varies

This displays Counts. This is the current numeric value of the passenger temperature door as monitored by the HVAC module.

Right Temp. Dr. Commanded

--

Varies

This displays Counts. This is the numeric value of the passenger mode door as commanded by the HVAC module.


HVAC Control Module Scan Tool Output Controls

Output Control

Description

A/C Request

This command allows you to turn the A/C Relay On and Off. When the A/C Relay is commanded On, the A/C compressor clutch should be engaged.

Afterblow Option

The rear HVAC/RSA module will illuminate all indicators and display segments on the module display.

Air Inlet Door

When Outside is selected, the HVAC control module commands the recirculation actuator toward the outside air position. When Recirc is selected, the HVAC control module commands the recirculation actuator toward the recirculation position. This is shown through a command of On and Off.

All Status LEDs

All HVAC status LEDs illuminate when ON is selected and turn off when OFF is selected.

Auxiliary Air Temp. Door

When Cold is selected, the HVAC control module commands the rear air temperature actuator to the full cold position. When Hot is selected, the HVAC control module commands the rear air temperature actuator to the full hot position.

Auxiliary Blower Motor

When ON is selected, the HVAC control module commands the blower motor relay ON and an increase or decrease of air. When OFF is selected, the HVAC control module commands the blower motor relay OFF.

Auxiliary Mode Door

When ON is selected, the HVAC control module commands the blower motor relay ON and an increase or decrease of air. When OFF is selected, the HVAC control module commands the blower motor relay OFF.

Blower Motor

When ON is selected, the HVAC control module commands the blower motor relay ON and a command to increase or decrease air. When OFF is selected, the HVAC control module commands the blower motor relay OFF.

Instant OAT Update

This command updates the outside air temperature.

Left Temp. Door Position

This commands the right temperature door position from Cold to Hot.

Mode Door Position

When A/C is selected, the HVAC control module commands the mode actuator to the panel position. When Defrost is selected, the HVAC control module commands the actuator to the defrost position.

Rear Defog Request

The BCM must receive a Rear Defog request from the HVAC control module in order to enable the output control. The BCM de-energizes the Rear Defog relay located in the I/P BEC when OFF is selected. The relay remains de-energized until ON is selected.

Recalibrate All Motors

When ON is selected, all air temp and mode actuators have the capability to perform a recalibration.

Right Temp. Door Position

This commands the right temperature door position from Cold to Hot.