Hummer H2. Manual - part 1937

HVAC control module monitors the actual value of the duct air temperature input and accordingly 
positions the left air temperature door to achieve the desired duct air temperature. 

LH Heater Duct Actual  

The scan tool displays 0-255 counts. The voltage applied to the left lower duct air temperature input of 
the HVAC control module is converted to a number between 0 and 255 where 51 Counts is 
approximately equal to 1 V. 

LH Heater Duct Desired  

The scan tool displays 0-255 counts. The desired value of the left lower duct air temperature input. The 
HVAC control module monitors the actual value of the duct air temperature input and accordingly 
positions the left air temperature door to achieve the desired duct air temperature. 

Mode Door Actual  

The scan tool displays 0-255 counts. The voltage applied to the mode door position input of the HVAC 
control module is converted to a number between 0 and 255 where 51 Counts is approximately equal to 1 
V. 

Mode 1 Door Commanded  

The scan tool displays 0-255 counts. The scan tool displays the desired mode door position as determined 
by the HVAC control module. 

Mode Motor Drive  

The scan tool displays Stop, Increase, or Decrease. The scan tool displays the control decision for the 
actuator output as determined by the HVAC control module. 

Mode Select Position  

The scan tool displays Off, Auto, Defrost, Heater, Htr/Def, Bi-Level, Panel. The scan tool displays the 
state of mode operation. 

Mode Switch  

The scan tool displays On/Off. The scan tool displays On when the mode switch is active. The scan tool 
displays Off when the mode switch is inactive. 

Off Switch  

The scan tool displays On/Off. The scan tool displays On when the Off switch is active. The scan tool 
displays Off when the Off switch is inactive.

 

2004 Hummer H2 

2004 HVAC HVAC Systems - Automatic - Hummer H2

  

Outside Air Temp. Filtered  

The scan tool displays -40 to 215° C (-40 to 419° F). The current value of the ambient air temperature 
display on the HVAC control module. 

Outside Air Temp. Raw  

The scan tool displays -40 to 215° C (-40 to 419° F). The voltage applied to the HVAC control module 
input from the ambient air temperature sensor is converted to an unfiltered temperature value. 

Pressure Cycle Switch  

The scan tool displays Low Pressure/Normal. The current state of the input from the A/C low pressure 
switch. The scan tool displays Low Pressure when the switch is open and displays Normal when the 
switch is closed. The low pressure switch opens when low side pressure decreases to 138-172 kPa (20-25 
psi) and closes when the low side pressure increases to approximately 275-317 kPa (40-46 psi) as 
measured at the switch/accumulator. 

Rear Defrost Switch  

The scan tool displays On/Off. The scan tool displays On when the rear defrost switch is active. The scan 
tool displays Off when the rear defrost switch is inactive. 

Recirculate Switch  

The scan tool displays On/Off. The scan tool displays On when the recirculation switch is active. The 
scan tool displays Off when the recirculation switch is inactive. 

RH AC Duct Actual  

The scan tool displays 0-255 counts. The voltage applied to the right upper duct air temperature input of 
the HVAC control module is converted to a number between 0 and 255 where 51 Counts is 
approximately equal to 1 V. 

RH AC Duct Desired  

The scan tool displays 0-255 counts. The desired value of the right upper duct air temperature input. The 
HVAC control module monitors the actual value of the duct air temperature input and accordingly 
positions the right air temperature door to achieve the desired duct air temperature. 

RH Heater Duct Actual  

The scan tool displays 0-255 counts. The voltage applied to the right lower duct air temperature input of 
the HVAC control module is converted to a number between 0 and 255 where 51 Counts is 
approximately equal to 1 V. 

RH Heater Duct Desired  

 

2004 Hummer H2 

2004 HVAC HVAC Systems - Automatic - Hummer H2

  

The scan tool displays 0-255 counts. The desired value of the right lower duct air temperature input. The 
HVAC control module monitors the actual value of the duct air temperature input and accordingly 
positions the right air temperature door to achieve the desired duct air temperature. 

Right Mix Door Actual  

The scan tool displays 0-255 counts. The voltage applied to the right air temperature door position input 
of the HVAC control module is converted to a number between 0 and 255 where 51 Counts is 
approximately equal to 1 V. 

Right Motor Drive  

The scan tool displays Stop, Increase, or Decrease. The scan tool displays the control decision for the 
actuator output as determined by the HVAC control module. 

Right Solar Sensor  

The scan tool displays 0-255 counts. The voltage applied to the BCM input from the right sunload sensor 
is converted to a number between 0 and 255 where 51 Counts is approximately equal to 1 V. 

Right Temp. Setting  

The scan tool displays 15 to 32° C (60 to 90° F). The scan tool displays the selected temperature from the 
right air temperature switch. 

DIAGNOSTIC TROUBLE CODE (DTC) LIST 

Diagnostic Trouble Code (DTC) List 

DTC

Diagnostic Procedure

Module

B0159

DTC B0159

HVAC Control Module

B0164

DTC B0164

HVAC Control Module

B0174

DTC B0174, B0179, B0510, or B0515

HVAC Control Module

B0179

DTC B0174, B0179, B0510, or B0515

HVAC Control Module

B0183

DTC B0183 or B0188

BCM

B0188

DTC B0183 or B0188

BCM

B0229

DTC B0229, B0414, B0424, or B3770

HVAC Control Module

B0263

DTC B0263, B0268, B0408, or B0418

HVAC Control Module

B0268

DTC B0263, B0268, B0408, or B0418

HVAC Control Module

B0408

DTC B0263, B0268, B0408, or B0418

HVAC Control Module

B0414

DTC B0229, B0414, B0424, or B3770

HVAC Control Module

B0418

DTC B0263, B0268, B0408, or B0418

HVAC Control Module

B0424

DTC B0229, B0414, B0424, or B3770

HVAC Control Module

B0510

DTC B0174, B0179, B0510, or B0515

HVAC Control Module

B0515

DTC B0174, B0179, B0510, or B0515

HVAC Control Module

 

2004 Hummer H2 

2004 HVAC HVAC Systems - Automatic - Hummer H2

  

DTC B0159 

Circuit Description 

The ambient air temperature sensor allows the HVAC control module to monitor the temperature of the air 
surrounding the front of the vehicle. The module applies 5 volts to internal input resistors that are connected to 
the signal circuit of the ambient air temperature sensor. The module provides ground to the ambient air 
temperature sensor through the low reference circuit. The HVAC control module monitors the voltage drop 
across the ambient air temperature sensor and uses the input for automatic control calculations. When the air 
temperature is cold, the resistance of the sensor is high and the voltage signal is high. When the air temperature 
is hot, the resistance of the sensor is low and the voltage signal is low. 

Conditions for Running the DTC 

z

Battery voltage to the HVAC control module is greater than 8.7 V and less than 16.5 V.  

z

The ignition is turned ON.  

Conditions for Setting the DTC 

The HVAC control module determines that the voltage applied to the input for the ambient air temperature 
sensor is less than 0.09 V or greater than 4.9 V. 

Action Taken When the DTC Sets 

The scan tool displays 10° C (50° F) as the value for the Outside Air Temp. Raw parameter. 

Conditions for Clearing the DTC 

z

The DTC will become history if the HVAC control module no longer detects the condition that set the 
DTC.  

z

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

z

The DTC can be cleared with a scan tool.  

Diagnostic Aids 

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

Test Description 

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

B1375

DTC B1375

HVAC Control Module

B3770

DTC B0229, B0414, B0424, or B3770

HVAC Control Module

P0530

DTC P0530

Powertrain Control Module

 

2004 Hummer H2 

2004 HVAC HVAC Systems - Automatic - Hummer H2