Hummer H2. Manual - part 1951

AIR DELIVERY IMPROPER 

Diagnostic Aids 

z

The condition may be intermittent. Refer to Testing for Intermittent Conditions and Poor 
Connections in Wiring Systems.  

z

Inspect the air delivery system for the following conditions: 

z

An obstruction to the airflow  

z

Air leaks  

z

Misaligned air ducts  

z

Broken or binding linkages or doors  

Air Delivery Improper 

25

z

Air Temperature Sensor Replacement - 
Upper Left  

z

Air Temperature Sensor Replacement - 
Lower Left  

z

Air Temperature Sensor Replacement - 
Lower Right  

 
Did you complete the replacement?

-

Go to Step 29

-

26

Replace the sunload sensor. Refer to Sun Load 
Sensor Replacement . 
Did you complete the replacement?

-

Go to Step 29

-

27

Replace the inside air temperature sensor assembly. 
Refer to Inside Air Temperature Sensor 
Assembly Replacement . 
Did you complete the replacement?

-

Go to Step 29

-

28

Replace the HVAC control module. Refer to 
HVAC Control Module Replacement . 
Did you complete the replacement?

-

Go to Step 29

-

29

Operate the system in order to verify the repair. 
Did you correct the condition?

-

System OK

Go to Step 3

Step

Action

Yes

No

Schematic Reference: HVAC Schematics 
Connector End View Reference: HVAC Connector End Views

1

Did you perform the HVAC Diagnostic System Check?

Go to Step 2

Go to Diagnostic 

System Check - HVAC 

Systems - Automatic

2

1. Turn ON the ignition, with the engine OFF.  

2. Place the blower motor switch in the OFF position.  

 

2004 Hummer H2 

2004 HVAC HVAC Systems - Automatic - Hummer H2

  

AIR RECIRCULATION MALFUNCTION 

Air Recirculation Malfunction 

Is the blower motor OFF?

Go to Step 3

Go to Blower Motor 

Always On

3

Place the blower motor switch in each speed position. 
Does the blower motor operate in any of the speed 
positions?

Go to Step 4

Go to Blower Motor 

Inoperative

4

Does the blower motor operate in each speed position?

Go to Step 5

Go to Blower Motor 

Malfunction

5

1. With a scan tool, observe the Mode Switch 

parameter in the Heating and Air Conditioning data 
list.  

2. Activate the mode switch.  

Does the scan tool indicate that the Mode Switch 
parameter changes state?

Go to Step 6

Go to Step 7

6

1. Place the blower motor switch in the maximum 

speed position.  

2. Place the mode switch in the bi-level position.  

3. Place the recirculation switch in the ON position.  

4. Observe the drive shaft of the recirculation actuator. 

5. Place the recirculation switch in the OFF position.  

Does the recirculation door move from the recirculation 
position to the outside air position?

Go to 

Diagnostic 

Aids

Go to Air Recirculation 

Malfunction

7

Inspect for poor connections at the harness connector of 
the HVAC control module. Refer to Testing for 
Intermittent Conditions and Poor Connections and 
Connector Repairs in Wiring Systems. 
Did you find and correct the condition?

Go to Step 9

Go to Step 8

8

Replace the HVAC control module. Refer to HVAC 
Control Module Replacement . 
Did you complete the replacement?

Go to Step 9

-

9

Operate the system in order to verify the repair. 
Did you correct the condition?

System OK

Go to Step 2

Step

Action

Yes

No

Schematic Reference:HVAC Schematics 
Connector End View Reference: HVAC Connector End Views 
DEFINITION: Air recirculation is inoperative or is always ON.

1

Did you perform the HVAC Diagnostic System 
Check?

Go to Diagnostic 

System Check - 

 

2004 Hummer H2 

2004 HVAC HVAC Systems - Automatic - Hummer H2

  

RE-CALIBRATING ACTUATORS 

When replacing the HVAC control module it will be necessary to allow the HVAC control module to perform a 
calibration process. When installing the HVAC control module be sure to perform the following: 

1. Place the ignition switch to the OFF position.  

2. Disconnect the scan tool.  

3. Install the HVAC control module.  

4. Connect all previously disconnected components.  

5. Place the ignition switch in the RUN position.  

6. Wait 40 seconds for the HVAC control module to self-calibrate.  

7. Verify that no DTCs have set as current DTCs.  

When replacing a HVAC actuator it will be necessary to allow the HVAC control module to perform a 
calibration process. When installing the HVAC actuator be sure to perform one of the following: 

Go to Step 2

HVAC Systems - 

Automatic

2

1. Turn ON the ignition, with the engine OFF.  

2. With a scan tool observe the Recirculate 

Switch Parameter.  

3. Activate the recirculation switch.  

Does the scan tool indicate that the Recirculate 
Switch Parameter changes state?

Go to Testing for 

Intermittent 

Conditions and Poor 

Connections

Go to Step 3

3

Inspect for poor connections at the harness connector 
of the HVAC control module. Refer to Testing for 
Intermittent Conditions and Poor Connections 
and Connector Repairs in Wiring Systems. 
Did you find and correct the condition?

Go to Step 5

Go to Step 4

4

Replace the HVAC control module. Refer to HVAC 
Control Module Replacement . 
Did you complete the replacement?

Go to Step 5

-

5

Operate the system in order to verify the repair. 
Did you correct the condition?

System OK

Go to Step 2

IMPORTANT: Do not adjust any controls on the HVAC control module while the HVAC control 

module is self-calibrating. If interrupted, improper HVAC performance will 
result.

IMPORTANT: Do not adjust any controls on the HVAC control module while the HVAC control 

module is self-calibrating. If interrupted, improper HVAC performance will 
result.

 

2004 Hummer H2 

2004 HVAC HVAC Systems - Automatic - Hummer H2

  

Preferred Method (w/Scan Tool) 

1. Clear all DTCs.  

2. Place the ignition switch in the OFF position.  

3. Install the HVAC actuator.  

4. Connect all previously disconnected components.  

5. Place the ignition switch in the RUN position.  

6. With the scan tool, initiate the Motor Re-calibration feature of the Heating and Air Conditioning Special 

Functions menu.  

7. Verify that no DTCs have set as current DTCs.  

Alternate Method (w/o Scan Tool) 

1. Clear all DTCs.  

2. Place the ignition switch to the OFF position.  

3. Install the HVAC actuator.  

4. Connect all previously disconnected components.  

5. Remove the HVAC B fuse for a minimum of 10 seconds.  

6. Install the HVAC B fuse.  

7. Place the ignition switch in the RUN position.  

8. Wait 40 seconds for the HVAC control module to self-calibrate.  

9. Verify that no DTCs have set as current DTCs.  

REPAIR INSTRUCTIONS 

HVAC CONTROL MODULE REPLACEMENT 

Removal Procedure 

IMPORTANT: Do not adjust any controls on the HVAC control module while the HVAC control 

module is self-calibrating. If interrupted, improper HVAC performance will 
result.

 

2004 Hummer H2 

2004 HVAC HVAC Systems - Automatic - Hummer H2