Hummer H2. Manual - part 243

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

2: Lack of communication may be due to a partial malfunction of the class 2 serial data circuit. The
specified procedure will determine the particular condition.

4: The Symptom Table will determine the correct diagnostic procedure to use.

5: The presence of DTCs which begin with "U" indicate some other module is not communicating. The
specified procedure will compile all the available information before tests are performed.

Diagnostic System Check - Defogger

Step

Action

Yes

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

Go to Step 2

Go to Scan Tool Does

Not Power Up in Data

Link Communications

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

2. Attempt to establish communication with

the following:

HVAC Control Module

Body Control Module (BCM)

Does the scan tool communicate with the
modules?

Go to Step 3

Go to Scan Tool Does

Not Communicate

with Class 2 Device in

Data Link

Communications

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 Class 2 Power
Mode on the Scan Tool. Refer to the Serial
Data Power Mode table within the Body
Control System Description and
Operation in Body Control System, for a
list of the power mode states that correspond
to each ignition switch position.

Does the Class 2 Power Mode parameter reading
match the ignition switch position for all the
selected 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 4

Go to Power Mode

Mismatch in Body

Control System

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

HVAC Control Module.

2004 Hummer H2

2004 ACCESSORIES & EQUIPMENT Stationary Windows - Hummer H2

SCAN TOOL OUTPUT CONTROLS

Body Control Module (BCM)

SCAN TOOL DATA LIST

Body Control Module (BCM)

SCAN TOOL DATA DEFINITIONS

Body Control Module (BCM)

Rear Defog Relay

The scan tool displays On or Off. When the BCM energizes the RR DEFOG relay, the scan tool will
display On. When the BCM de-energizes the RR DEFOG relay, the scan tool will display Off.

DIAGNOSTIC TROUBLE CODE (DTC) LIST

Diagnostic Trouble Code (DTC) List

DTC B0283

BCM

Does the scan tool display any DTCs?

Go to Step 5

Go to Symptoms -

Stationary Windows

Does the scan tool display DTCs that begin with
"U"?

Go to Diagnostic

Trouble Code (DTC)

List in Data Link

Communications

Go to Step 6

Does the scan tool display DTC B1000 or B1440?

Go to Diagnostic

Trouble Code (DTC)

List in Body Control

System

Go to Diagnostic

Trouble Code (DTC)

List

Scan Tool

Output Control

Additional Menu

Selection(s)

Description

Rear Defogger

The BCM actuates the rear window defogger relay when you
select ON. The rear window defogger grid should become warm.

Scan Tool Parameter

Data List

Units Displayed

Typical Data Value

Ignition On/Engine Off

Rear Defog Relay

Outputs

On/Off

Off

DTC

Diagnostic Procedure

Module(s)

B0283

DTC B0283

BCM

2004 Hummer H2

2004 ACCESSORIES & EQUIPMENT Stationary Windows - Hummer H2

Circuit Description

The body control module (BCM) monitors the voltage level on the control circuit of the DEFOG relay. The
voltage level should be near system voltage while the DEFOG relay is de-energized. The voltage will be pulled
low when the BCM energizes the DEFOG relay. The BCM tests the control circuit of the DEFOG relay every
125 milliseconds.

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC

One of the following conditions will cause this DTC to set:

The BCM detects a high voltage level on the control circuit of the DEFOG relay, while the relay is
energized.

The BCM detects a low voltage level or an open on the control circuit of the DEFOG relay, when
commanding the relay On.

Action Taken When the DTC Sets

The rear window defogger will be disabled until the condition is no longer present.

Conditions for Clearing the DTC

A current DTC clears when the malfunction is no longer present.

A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat
of the malfunction.

Test Description

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

2: Listen for an audible click when the DEFOG relay operates. Command both the ON and OFF states.
Repeat the commands as necessary.

3: Tests for voltage at the coil side of the DEFOG relay. The HVAC fuse supplies power to the coil side
of the DEFOG relay.

4: Verifies that the BCM is providing ground to the DEFOG relay.

5: Tests if ground is constantly being applied to the DEFOG relay.

6: Tests for an open on the control circuit of the DEFOG relay.

DTC B0283

Step

Action

Yes

Schematic Reference:Defogger Schematics

2004 Hummer H2

2004 ACCESSORIES & EQUIPMENT Stationary Windows - Hummer H2

Connector End View Reference:Stationary Windows Connector End Views

Did you perform the Defogger Diagnostic System
Check?

Go to Step 2

Go to Diagnostic

System Check -

Defogger

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

2. Select from miscellaneous test, the Rear

Defogger from the BCM output controls.

3. With a scan tool, command the DEFOG relay

ON and OFF.

Do you hear a click when you command the
DEFOG relay ON and OFF?

Go to Testing for

Intermittent Conditions

and Poor Connections in

Wiring Systems

Go to Step 3

1. Turn OFF the ignition.

2. Disconnect the DEFOG relay.

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

4. Connect a test lamp between the ignition

voltage circuit of the DEFOG relay coil and a
good ground.

Does the test lamp illuminate?

Go to Step 4

Go to Step 10

1. Connect a test lamp between the control

circuit of the DEFOG relay and the ignition
voltage circuit of the DEFOG relay coil.

2. With a scan tool, command the DEFOG relay

ON and OFF.

Does the test lamp turn ON and OFF with each
command?

Go to Step 8

Go to Step 5

Does the test lamp remain illuminated with each
command?

Go to Step 7

Go to Step 6

Test the control circuit of the DEFOG relay for an
open or a short to voltage. Refer to Circuit Testing
and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?

Go to Step 13

Go to Step 9

Test the control circuit of the DEFOG relay 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 13

Go to Step 9

Inspect for poor connections at the DEFOG relay.
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 13

Go to Step 11

2004 Hummer H2

2004 ACCESSORIES & EQUIPMENT Stationary Windows - Hummer H2

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