Hummer H2. Manual - part 694

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: 

z

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

z

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 

z

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

z

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

No

Schematic Reference:Defogger Schematics 

 

2004 Hummer H2 

2004 ACCESSORIES & EQUIPMENT Stationary Windows - Hummer H2

  

Connector End View Reference:Stationary Windows Connector End Views

1

Did you perform the Defogger Diagnostic System 
Check?

Go to Step 2

Go to Diagnostic 

System Check - 

Defogger

2

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

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

4

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

5

Does the test lamp remain illuminated with each 
command?

Go to Step 7

Go to Step 6

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

7

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

8

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

  

SYMPTOMS - STATIONARY WINDOWS 

1. Perform the Diagnostic System Check - Defogger before using the symptom tables in order to verify 

that all of the following are true: 

z

There are no DTCs set.  

z

The control modules can communicate via the serial data link.  

2. Review the system operation in order to familiarize yourself with the system functions. Refer to Rear 

Window Defogger Description and Operation .  

Visual/Physical Inspection 

z

Inspect for aftermarket devices which could affect the operation of the rear window defogger or the 

9

Inspect for poor connections at the harness 
connector of the BCM. 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 12

10

Repair an open or high resistance in ignition voltage 
circuit of the DEFOG relay coil. Refer to Wiring 
Repairs in Wiring Systems. 
Did you complete the repair?

Go to Step 13

-

11

Replace the DEFOG relay. 
Did you complete the replacement?

Go to Step 13

-

12

Replace the BCM. Refer to Body Control Module 
Replacement in Body Control System.Did you 
complete the replacement?

IMPORTANT:

Perform the set up procedure for the Body 
Control Module (BCM). Refer to Body Control 
Module (BCM) Programming/RPO Configuration 
in Body Control System.

Go to Step 13

-

13

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

2. Operate the vehicle within the Conditions for 

Setting the DTC as specified in the supporting 
text.  

Does the DTC reset?

Go to Step 2

System OK

IMPORTANT: For the inside rearview mirror with the automatic day-night feature, review the 

system operation in order to familiarize yourself with the system functions. 
Refer to Automatic Day-Night Mirror Description and Operation . 
For the rear window defogger system, the following steps must be performed 
before using the symptom tables:

 

2004 Hummer H2 

2004 ACCESSORIES & EQUIPMENT Stationary Windows - Hummer H2

  

automatic day-night feature of the inside rearview mirror. Refer to Checking Aftermarket Accessories
in Wiring Systems.  

z

Inspect the easily accessible or visible system components for obvious damage or conditions which could 
cause the symptom.  

Intermittent 

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for 
Intermittent Conditions and Poor Connections in Wiring Systems. 

Symptom List 

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom: 

z

Defogger Inoperative - Rear Window  

z

Defogger Grid Lines Diagnosis  

z

Mirrors - Automatic Day-Night Inoperative  

z

Mirrors - Temperature Displays SC or OC  

z

Mirrors - Compass Display Inoperative or Inaccurate  

z

Mirrors - Temperature Display Inaccurate  

DEFOGGER INOPERATIVE - REAR WINDOW 

Defogger Inoperative - Rear Window 

Step

Action

Yes

No

Schematic Reference:Defogger Schematics 
Connector End View Reference:Stationary Windows Connector End Views

1

Did you perform the Defogger Diagnostic System 
Check?

Go to Step 2

Go to Diagnostic 

System Check - 

Defogger

2

1. Start the engine.  

2. Depress the rear window defogger switch.  

3. Observe the rear window defogger indicator 

on the HVAC Control Module.  

Does the rear window defogger indicator illuminate?

Go to Step 3

Go to Step 8

3

Connect a test lamp between the left side of the rear 
window defogger grid and a good ground. 
Does the test lamp illuminate?

Go to Step 4

Go to Step 5

4

Connect a test lamp between the left side of the rear 
window defogger grid and the right side of the rear 
window defogger grid. 
Does the test lamp illuminate?

Go to Testing for 

Intermittent Conditions 

and Poor Connections in 

Wiring Systems

Go to Step 10

 

2004 Hummer H2 

2004 ACCESSORIES & EQUIPMENT Stationary Windows - Hummer H2