Hummer H2. Manual - part 186

Action Taken When the DTC Sets 

The BCM implements default actions for each ignition switch position when faults are detected. 

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.  

DTC B1440 

Active

On

Off

No

Inactive

On

Off

Yes

Inactive

1

On

On

Yes

Active

Off

Off

Yes

Active

Off

On

Yes

Active

On

Off

Yes

1

 The module sets the DTC 1 minute after it detects the condition.

Step

Action

Yes

No

Schematic Reference:Body Control System Schematics 
Connector End View Reference: Body Control System Connector End Views

1

Perform the Diagnostic System Check for the system exhibiting the 
symptom. Refer to Control Module References . 
Did you perform the Diagnostic System Check?

Go to 

Step 2

Go to Control 

Module 

References

2

1. Install a scan tool.  

2. Turn OFF the ignition.  

3. With a scan tool, monitor the following in Body Control Module, 

Data Display, Inputs: 

z

Ignition 0  

z

Ignition 1  

z

Ignition Accessory  

Does the scan tool indicate that all inputs are inactive/Off?

Go to 

Step 3

Go to Step 6

3

1. Install a scan tool.  

2. Turn the ignition switch to ACC.  

3. With a scan tool, monitor the following in Body Control Module, 

Data Display, Inputs: 

z

Ignition 0  

z

Ignition 1  

z

Ignition Accessory  

 

2004 Hummer H2 

2004 ACCESSORIES & EQUIPMENT Body Control System - Hummer H2

  

Does the scan tool indicate that the Ignition 0 and Ignition Accessory 
inputs are active/On?

Go to 

Step 4

Go to Step 8

4

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

2. With a scan tool, monitor the following in Body Control Module, 

Data Display, Inputs: 

z

Ignition 0  

z

Ignition 1  

z

Ignition Accessory  

Does the scan tool indicate that the all inputs are active/On?

Go to 

Step 5

Go to Step 8

5

1. Turn the ignition switch to START.  

2. With a scan tool, monitor the following in Body Control Module, 

Data Display, Inputs: 

z

Ignition 0  

z

Ignition 1  

z

Ignition Accessory  

Does the scan tool indicate that the Ignition 0 and Ignition 1 inputs are 
On and the Ignition Accessory input is inactive?

IMPORTANT:

The engine may start in this step. Turn the engine OFF immediately 
after reviewing the input data.

Go to 

Step 

11

Go to Step 8

6

1. Disconnect the ignition switch harness connectors.  

2. With a scan tool, monitor the following in Body Control Module, 

Data Display, Inputs: 

z

Ignition 0  

z

Ignition 1  

z

Ignition Accessory  

Does the scan tool indicate that any of the Ignition 0, Ignition 1 or 
Ignition Accessory inputs is active/On?

Go to 

Step 7

Go to Step 9

7

1. Disconnect the body control module (BCM) harness connectors.  

2. Test the suspect ignition switch input circuits for a short to 

voltage. Refer to Circuit Testing and Wiring Repairs in Wiring 
Systems.  

Did you find and correct the condition?

Go to 

Step 

14

Go to Step 11

1. Disconnect the ignition switch connectors.  

2. Install a 3A fused jumper between the suspect circuits and an 

 

2004 Hummer H2 

2004 ACCESSORIES & EQUIPMENT Body Control System - Hummer H2

  

DTC C0550 

Circuit Description 

The internal fault detection is handled inside the control module. No external circuits are involved.

8

ignition switch B+ supply.  

3. With a scan tool, monitor the suspect circuits in Body Control 

Module, Data Display, Inputs: 

z

Ignition 0  

z

Ignition 1  

z

Ignition Accessory  

Does the scan tool indicate that the suspect circuits are now active/On?

Go to 

Step 9

Go to Step 10

9

Inspect for poor connections at the ignition switch harness connectors. 
Refer to Testing for Intermittent Conditions and Poor Connections 
andConnector Repairs in Wiring Systems. 
Did you find and correct the condition?

Go to 

Step 

14

Go to Step 12

10

1. Disconnect the BCM harness connectors.  

2. Test the suspect ignition switch input circuits for a short to 

ground or an open. Refer to Circuit Testing andWiring Repairs
in Wiring Systems.  

Did you find and correct the condition?

Go to 

Step 

14

Go to Step 11

11

Inspect for poor connections at the BCM harness connectors. 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 

14

Go to Step 13

12

Replace the ignition switch. Refer to Ignition Switch Replacement in 
Steering Wheel and Column. 
Did you complete the replacement?

Go to 

Step 

14

-

13

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

IMPORTANT:

Perform the programming or setup procedure for the module, if 
required.

Go to 

Step 

14

-

14

1. Reconnect all components.  

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

3. 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 ACCESSORIES & EQUIPMENT Body Control System - Hummer H2

  

Conditions for Running the DTC 

The microprocessor runs the program to detect an internal fault when power up is commanded. The only 
requirements are voltage and ground. This program runs even if the voltage is out of the valid operating range. 

Conditions for Setting the DTC 

z

The control module detects an internal write malfunction.  

z

The control module detects an internal checksum malfunction.  

Action Taken When the DTC Sets 

If equipped, the following module specific actions may occur: 

z

The ABS indicator turns ON.  

z

The BRAKE Warning indicator turns ON.  

z

The TCS indicator turns ON.  

z

The EBCM disables the ABS/DRP/TCS.  

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.  

Diagnostic Aids 

z

This DTC may be stored as a history DTC without affecting the operation of the module. If stored only as 
a history DTC and not retrieved as a current DTC, do not replace the module.  

z

If this DTC is retrieved as both a current and history DTC, replace the module.  

z

If this DTC continues to set intermittently, replace the module  

DTC C0550 

Step

Action

Yes

No

1

Did you perform the Diagnostic System Check for the 
system exhibiting the symptom?

Go to 

Step 2

Go to Control Module 

References for the applicable 

Diagnostic System Check

2

1. Install a scan tool.  

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

3. Retrieve DTCs.  

Is the DTC retrieved as a current DTC?

Go to 

Step 3

Go to Diagnostic Aids

IMPORTANT:

 

2004 Hummer H2 

2004 ACCESSORIES & EQUIPMENT Body Control System - Hummer H2