Hummer H2. Manual - part 1935

1

Point - Heating, Ventilation and Air 
Conditioning?

Go to Step 2

Point - Heating, Ventilation 

and Air Conditioning in 

Heating, Ventilation and Air 

Conditioning

2

Install a scan tool. 
Does the scan tool power up?

Go to Step 3

Go to Scan Tool Does Not 

Power Up in Data Link 

Communications

3

1. Turn ON the ignition, with the 

engine OFF.  

2. Attempt to establish 

communication with the 
following control modules: 

z

HVAC Control Module  

z

Body Control Module  

z

Powertrain Control 
Module  

Does the scan tool communicate with 
the control modules?

Go to Step 4

Go to Scan Tool Does Not 

Communicate with Class 2 

Device in Data Link 

Communications

4

1. Access the Class 2 Power 

Mode in the Diagnostic Circuit 
Check on the scan tool.  

2. Rotate the ignition switch 

through all positions while 
observing the Ignition Switch 
Power Mode parameter.  

Does the Ignition Switch parameter 
reading match the ignition switch 
position for all switch positions?

IMPORTANT:

The engine may start during the 
following step. Turn OFF the 
engine as soon as you have 
observed the Crank power mode.

Go to Step 5

Go to Power Mode Mismatch 

in Body Control System

5

Select the display DTCs function on 
the scan tool for the following 
modules: 

z

HVAC Control Module  

z

Body Control Module  

z

Powertrain Control Module  

 

2004 Hummer H2 

2004 HVAC HVAC Systems - Automatic - Hummer H2

  

SCAN TOOL OUTPUT CONTROLS 

HVAC Control Module Scan Tool Output Controls 

 
Does the scan tool display any 
DTCs?

Go to Step 6

Go to Symptoms - HVAC 

Systems - Automatic

6

Does the scan tool display any DTCs 
which begin with a "U"?

Go to Scan Tool Does Not 

Communicate with Class 

2 Device in Data Link 

Communications

Go to Step 7

7

Does the scan tool display DTC 
B10XX?

Go to Diagnostic Trouble 

Code (DTC) List in Body 

Control Systems

Go to Step 8

8

Does the scan tool display any DTCs 
that are associated with the charging 
system?

Go to Diagnostic Trouble 

Code (DTC) List in 

Engine Electrical

Go to Step 9

9

Does the scan tool display any DTCs 
that are associated with the HVAC 
system?

Go to Diagnostic Trouble 

Code (DTC) List

Go to Diagnostic Trouble 

Code (DTC) List in Engine 

Controls - 4.8L, 5.3L, and 6.0L

Scan Tool 

Output 

Control

Additional 

Menu Selection

(s)

Description

A/C 
Permission

Miscellaneous 
Tests

When you select ON, the HVAC control module changes the state of 
the A/C Permission parameter to Granted and transmits a clutch 
enable message to the PCM over the class 2 serial data circuit. The 
A/C compressor clutch engages and remains engaged until you select 
OFF. When you select OFF, the HVAC control module changes the 
state of the A/C Permission parameter to Withheld and transmits a 
clutch disable message to the PCM over the class 2 serial data circuit.

Air Inlet Door

Motor/Actuator 
Tests

When you select ON, the HVAC control module commands the 
recirculation actuator toward the maximum door position. The 
actuator moves the door to the recirculation position. When you select 
OFF, the HVAC control module commands the recirculation actuator 
toward the minimum door position. The actuator moves the door to 
the outside air position.

Blower Motor

Motor/Actuator 
Tests

When you select ON, the HVAC control module commands the 
blower motor to maximum speed. The blower motor operates at 
maximum speed until you select OFF. The HVAC control module 
must be in the ON state before selecting the output control.

HVAC 
Actuator 
Recalibration

-

When you select RESET, the HVAC control module recalibrates the 
maximum and minimum door positions of each HVAC door. The 
ambient air temperature display is set to the current value of the 
Outside Air Temp. Raw parameter.

Inside Air 

Motor/Actuator  When you select OFF, the HVAC control module commands the 

 

2004 Hummer H2 

2004 HVAC HVAC Systems - Automatic - Hummer H2

  

PCM Scan Tool Output Controls 

SCAN TOOL DATA LIST 

BCM Scan Tool Data List 

HVAC Control Module Scan Tool Data List 

Temperature 
Fan

Tests

inside air temperature fan OFF. The fan remains OFF until you select 
ON. The normal state of the inside air temperature fan is ON.

Instant OAT 
Update

Miscellaneous 
Tests

The scan tool displays OFF or ON. This function updates the HVAC 
control module ambient air temperature input to the current raw 
value.

Left Mix 
Motor

Motor/Actuator 
Tests

When you select ON, the HVAC control module commands the left 
air temperature actuator toward the maximum door position. The 
actuator moves the door to the full hot position. When you select 
OFF, the HVAC control module commands the left air temperature 
actuator toward the minimum door position. The actuator moves the 
door to the full cold position.

Mode 1 Door 
Position

Motor/Actuator 
Tests

When you select ON, the HVAC control module commands the mode 
actuator toward the maximum door position. The actuator moves the 
door to the panel position. When you select OFF, the HVAC control 
module commands the mode actuator toward the minimum door 
position. The actuator moves the door to the floor position.

Right Mix 
Motor

Motor/Actuator 
Tests

When you select ON, the HVAC control module commands the right 
air temperature actuator toward the maximum door position. The 
actuator moves the door to the full cold position. When you select 
OFF, the HVAC control module commands the right air temperature 
actuator toward the minimum door position. The actuator moves the 
door to the full hot position.

Scan Tool 

Output 

Control

Additional 

Menu 

Selection(s)

Description

A/C Relay

Engine Output 
Controls

The engine must be running and the PCM must receive an A/C request 
from the HVAC control module in order to enable the output control. The 
PCM de-energizes the A/C compressor clutch relay when you select OFF. 
The relay remains de-energized until you select ON.

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)

Left Solar Sensor

Data

Counts/Volts

Varies

Right Solar Sensor

Data

Counts/Volts

Varies

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° 

 

2004 Hummer H2 

2004 HVAC HVAC Systems - Automatic - Hummer H2

  

F)

A/C Switch

Input/Output

On/Off

Off

AC Permission

Input/Output

Withheld/Granted

Varies

Air Inlet Door Actual

Door 

Positions

Counts

Varies

Air Inlet Commanded

Door 

Positions

Counts

Varies

Air Inlet Motor Drive

Door 

Positions

Stop, Increase, Decrease

Stop

Air Mix Door Left 
Commanded

Door 

Positions

Counts

Varies

Air Mix Door Right 
Commanded

Door 

Positions

Counts

Varies

Auto Switch

Input/Output

On/Off

Off

Battery Voltage

Input/Output

Volts

13.5-14.5 V

Blower Motor PWM Speed

Door 

Positions

Percent

12-114%

Dim Level Requested

Sensor Data

Percent

Varies

Engine Coolant Temp

Sensor Data

° C/° F

Varies

Fan Down Button

Input/Output

On/Off

Off

Fan Up Button

Input/Output

On/Off

Off

Front Defrost Switch

Input/Output

On/Off

Off

Ign. Since Current DTC

Input/Output

Cycles

0

Inside Air Temp. Sensor

Sensor Data

° C/° F

Varies

Inside Air Temp. Fan

Sensor Data

On/Off

On

Left Mix Door Actual

Door 

Positions

Counts

Varies

Left Mix Motor Drive

Door 

Positions

Stop, Increase, Decrease

Stop

Left Temp. Setting

Input/Output

° C/° F

Varies

LH AC Duct Actual

Sensor Data

Counts

Varies

LH AC Duct Desired

Sensor Data

Counts

Varies

LH Heater Duct Actual

Sensor Data

Counts

Varies

LH Heater Duct Desired

Sensor Data

Counts

Varies

Mode Door Actual

Door 

Positions

Counts

Varies

Mode Dr. Motor Command

Door 

Positions

Counts

Varies

Mode Motor Drive

Door 

Positions

Stop, Increase, Decrease

Stop

Mode Select Position

Door 

Positions

Off, Auto, Defrost, Heater, Htr/Def, Bi-

Level, Panel

Varies

 

2004 Hummer H2 

2004 HVAC HVAC Systems - Automatic - Hummer H2