Content .. 1937 1938 1939 1940 ..

Hummer H2. Manual - part 1939

sensors are high and the voltage signals are high. When the duct air temperatures are hot, the resistances of the
sensors are low and the voltage signals are low. The HVAC control module converts the voltage values to count
values where 1 V is approximately equal to 51 counts.

Conditions for Running the DTC

Battery voltage is within 8.7-16.5 V.

The ignition is ON.

Conditions for Setting the DTC

The HVAC control module determines that the value of the air temperature parameter is less than 5 counts or
greater than 250 counts.

Action Taken When the DTC Sets

The HVAC control module uses a default air temperature value for further automatic control calculations. The
default values are not displayed on the scan tool.

Conditions for Clearing the DTC

The DTC will become history if the HVAC control module no longer detects a fault.

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

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

2: Verifies that the temperature displayed is not within the calibrated range.

3: Tests for the proper operation of the circuit in the high voltage range.

4: Tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper opens
when you perform this test, the signal circuit is shorted to voltage.

DTC B0174, B0179, B0510, or B0515

Step

Action

Value

(s)

Yes

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

Did you perform the HVAC Diagnostic System

Go to Diagnostic

2004 Hummer H2

2004 HVAC HVAC Systems - Automatic - Hummer H2

Check?

Go to Step 2

System Check -

HVAC Systems -

Automatic

1. Install a scan tool.

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

3. With a scan tool, observe the appropriate Duct

Actual parameter in the Heating and Air
Conditioning data list. Refer to one of the
following parameters:

LH AC Duct Actual

LH Heater Duct Actual

RH AC Duct Actual

RH Heater Duct Actual

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

5-250

Counts

Go to

Diagnostic

Aids

Go to Step 3

1. Turn OFF the ignition.

2. Disconnect the air temperature sensor.

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

4. With a scan tool, observe the appropriate Duct

Actual data parameter.

Does the scan tool indicate that the Duct Actual data
parameter is greater than the specified value?

250

Counts

Go to Step 4

Go to Step 5

1. Turn OFF the ignition.

2. Connect a 3 amp fused jumper wire between the

signal circuit of the air temperature sensor and
the low reference circuit of the air temperature
sensor.

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

4. With a scan tool, observe the appropriate Duct

Actual data parameter.

Does the scan tool indicate that the Duct Actual data
parameter is less than the specified value?

Counts

Go to Step 8

Go to Step 6

Test the signal circuit of the air temperature sensor for
a short to ground. Refer to Circuit Testing and
Wiring Repairs in Wiring Systems.
Did you find and correct the condition?

Go to Step

Go to Step 9

Test the signal circuit of the air temperature sensor for
a short to voltage, a high resistance, or an open. Refer
to Circuit Testing and Wiring Repairs in Wiring

2004 Hummer H2

2004 HVAC HVAC Systems - Automatic - Hummer H2

DTC B0183 OR B0188

Circuit Description

Systems.
Did you find and correct the condition?

Go to Step

Go to Step 7

Test the low reference circuit of the air temperature
sensor for a high resistance or an open. Refer to
Circuit Testing and Wiring Repairs in Wiring
Systems.
Did you find and correct the condition?

Go to Step

Go to Step 9

Inspect for poor connections at the harness connector
of the air temperature sensor. 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

Go to Step 10

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

Go to Step 11

Replace the air temperature sensor. Refer to the
appropriate replacement procedure:

Air Temperature Sensor Replacement -
Upper Right

Air Temperature Sensor Replacement -
Upper Left

Air Temperature Sensor Replacement -
Lower Left

Air Temperature Sensor Replacement -
Lower Right

Did you complete the replacement?

Go to Step

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

Go to Step

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

2. Operate the vehicle within the Conditions for

Running the DTC as specified in the supporting
text.

Does the DTC reset?

Go to Step 2

System OK

2004 Hummer H2

2004 HVAC HVAC Systems - Automatic - Hummer H2

The following DTC's are for the left and right sunload sensors.

B0183 is for the left sunload sensor.

B0188 is for the right sunload sensor.

The left and right sunload sensors provide the HVAC control module with inputs as to the amount heat load the
sun is placing on the interior of the vehicle. The sunload sensors are photodiodes that are sensitive to light
intensity. The body control module (BCM) applies 5 volts to internal input resistors that are connected to the
left and right signal circuits of the sunload sensor assembly. The BCM provides ground to the sensors through
the low reference circuit. The BCM monitors the voltage drops across the sunload sensors and converts the
voltage values to count values where 1 V is approximately equal to 51 counts. As the light intensity increases,
the sunload sensors allow more current to travel through the circuits and the signal voltages decrease. As the
light intensity decreases, the sunload sensors allow less current to travel through the circuits and the signal
voltages increase. The BCM transmits the data to the HVAC control module over the class 2 serial data circuit.

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC

The BCM determines that the value of the sunload sensor signal is less than 5 counts or greater than 250 counts.

Action Taken When the DTC Sets

The action taken will be for the BCM to revert to a calibrated default value.

Conditions for Clearing the DTC

The DTC will become history if the BCM no longer detects a failure.

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

The DTC can be cleared with a scan tool.

Diagnostic Aids

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

Test Description

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

2: Verifies that the value displayed is within the specified range.

3: Tests for the proper operation of the circuit in the high voltage range.

4: Tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper opens
when you perform this test, the signal circuit is shorted to voltage.

2004 Hummer H2

2004 HVAC HVAC Systems - Automatic - Hummer H2

Content .. 1937 1938 1939 1940 ..