Hummer H2. Manual - part 1941

Go to Step 2

HVAC Systems - 

Automatic

2

1. Install a scan tool.  

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

3. With the scan tool, observe the appropriate Door 

Actual parameter in the Heating and Air 
Conditioning data list.  

Does the scan tool indicate that the appropriate Door 
Actual parameter is within the specified range?

5-250 

counts

Go to 

Diagnostic 

Aids

Go to Step 3

3

1. Turn OFF the ignition.  

2. Disconnect the appropriate HVAC door actuator. 

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

4. With a scan tool, observe the appropriate Door 

Actual parameter.  

Does the scan tool indicate that the appropriate Door 
Actual parameter is less than the specified value?

5 

counts

Go to Step 4

Go to Step 10

4

1. Turn OFF the ignition.  

2. Connect a 3-ampere fused jumper between the 

5-volt reference circuit and the appropriate door 
position signal circuit of the HVAC door 
actuator.  

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

4. With a scan tool, observe the appropriate Door 

Actual parameter.  

Does the scan tool indicate that the appropriate Door 
Actual parameter is greater than the specified value?

230 

counts

Go to Step 5

Go to Step 8

5

1. Disconnect the fused jumper.  

2. Measure the voltage between the 5-volt 

reference circuit and the low reference circuit of 
the HVAC door actuator.  

Does the voltage measure less than the specified 
value?

5.5 V

Go to Step 6

Go to Step 7

6

1. Turn OFF the ignition.  

2. Disconnect the negative battery cable.  

3. Measure the resistance from the low reference 

circuit of the HVAC door actuator to a good 
ground.  

5 ohm

 

2004 Hummer H2 

2004 HVAC HVAC Systems - Automatic - Hummer H2

  

Does the resistance measure less than the specified 
value?

Go to Step 

12

Go to Step 11

7

Test the 5-volt reference circuit of the appropriate 
HVAC door actuator for a short to voltage. Refer to 
Circuit Testing and to Wiring Repairs in Wiring 
Systems. 
Did you find and correct the condition?

-

Go to Step 

16

Go to Step 13

8

Test the 5-volt reference circuit of the appropriate 
HVAC door actuator for a short to ground, for a high 
resistance, or for an open. Refer to Circuit Testing 
and to Wiring Repairs in Wiring Systems. 
Did you find and correct the condition?

-

Go to Step 

16

Go to Step 9

9

Test the appropriate door position signal circuit of the 
HVAC door actuator for a short to ground, for a high 
resistance, or for an open. Refer to Circuit Testing 
and to Wiring Repairs in Wiring Systems. 
Did you find and correct the condition?

-

Go to Step 

16

Go to Step 13

10

Test the appropriate door position signal circuit of the 
HVAC door actuator for a short to voltage. Refer to 
Circuit Testing and to Wiring Repairs in Wiring 
Systems. 
Did you find and correct the condition?

-

Go to Step 

16

Go to Step 13

11

1. Disconnect the HVAC control module.  

2. Test the low reference circuit of the appropriate 

HVAC door actuator for a high resistance or for 
an open. Refer to Circuit Testing and to Wiring 
Repairs in Wiring Systems.  

Did you find and correct the condition?

-

Go to Step 

16

Go to Step 13

12

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

-

Go to Step 

16

Go to Step 14

13

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

-

Go to Step 

16

Go to Step 15

Replace the HVAC door actuator. Refer to the 

IMPORTANT:

Perform the calibration procedure for HVAC door 
actuators.

 

2004 Hummer H2 

2004 HVAC HVAC Systems - Automatic - Hummer H2

  

DTC B0263, B0268, B0408, OR B0418 

Circuit Description 

The following DTC's are for the HVAC door actuators: 

z

B0263 is for the mode actuator.  

z

B0268 is for the recirculation actuator.  

z

B0408 is for the left air temperature actuator.  

z

B0418 is for the right air temperature actuator.  

The HVAC control module controls the HVAC door actuators to regulate the airflow through the HVAC 
system. Each actuator consists of a stepper motor, a logic circuit, and a potentiometer. The potentiometer inside 
the door actuator allows the module to monitor the current position of the actuator drive shaft. The logic circuit 
inside the actuators receives control signals from the HVAC control module and controls the internal stepper 
motor. When a door positional change is required, the HVAC control module calculates a commanded door 
position. The module compares the commanded door position to the actual door position and determines the 
needed direction of motor rotation. The module applies a signal voltage to the door control circuit that is an 
input to the internal logic circuit of the door actuator. A 5 volt signal increases the door position. A 0 volt signal 
decreases the door position. When the commanded door position is equal to the actual door position, the HVAC 
control module sends a 2.5 volt signal to the door actuator and motor rotation stops. The ignition 3 voltage 
circuit provides source voltage to the logic circuit. The module provides ground to the actuator logic circuit 
through the low reference circuit. 

14

appropriate replacement procedure: 

z

Recirculation Actuator Replacement  

z

Mode Actuator Replacement  

z

Air Temperature Actuator Replacement - 
Right  

z

Air Temperature Actuator Replacement - 
Left  

Did you complete the replacement?

-

Go to Step 

16

-

15

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

-

Go to Step 

16

-

16

1. Use the scan tool in order to clear the DTCs.  

2. Operate the vehicle according to the Conditions 

for Running in the DTC, as specified in the 
supporting text.  

Does the DTC set again?

-

Go to Step 2

System OK

 

2004 Hummer H2 

2004 HVAC HVAC Systems - Automatic - Hummer H2

  

Conditions for Running the DTC 

z

Source voltage is 8.7-16.5 volts.  

z

The ignition is ON.  

z

The HVAC control module commands the actuator to move.  

Conditions for Setting the DTC 

The actual door position is not near the commanded door position. 

Action Taken When the DTC Sets 

The HVAC control module does not command the actuator to move for the remainder of the ignition cycle. 

Conditions for Clearing the DTC 

z

The DTC becomes history during the next ignition cycle in which the HVAC control module no longer 
detects a stall condition.  

z

The history DTC will clear after 100 fault free ignition cycles.  

z

The DTC can be cleared with a scan tool.  

Diagnostic Aids 

z

If the condition is not present refer to Testing for Intermittent Conditions and Poor Connections in 
Wiring Systems.  

z

Inspect the appropriate door and door actuator for the following conditions: 

{

A misaligned door actuator  

{

Binding linkages  

{

A binding door  

{

An obstruction that prevents the door actuator from operating within the full range of motion  

Test Description 

The numbers below refer to the step numbers on the diagnostic table. 

2: Determines if the HVAC door actuator is stalled.  

3: Applies control circuit voltages to the input of the HVAC door actuator.  

DTC B0263, B0268, B0408, or B0418 

Step

Action

Yes

No

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

Did you perform the HVAC Diagnostic System Check?

Go to Diagnostic 

System Check - 

 

2004 Hummer H2 

2004 HVAC HVAC Systems - Automatic - Hummer H2