Hummer H2. Manual — part 314

9

Test the signal circuit of the I/P
dimmer/headlamp switch for a short to ground, 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 16

Go to Step 13

10

Test the signal circuit of the I/P
dimmer/headlamp switch 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 16

Go to Step 13

11

1. Disconnect the body control module.

2. Test the low reference circuit of the I/P

dimmer/headlamp switch 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 16

Go to Step 13

12

Inspect for poor connections at the harness
connector of the I/P dimmer/headlamp switch.
Refer to Circuit Testing and Wiring Repairs in
Wiring Systems.
Did you find and correct the condition?

-

Go to Step 16

Go to Step 14

13

Inspect for poor connections at the harness
connector of the body control module. Refer to
Circuit Testing and Wiring Repairs in Wiring
Systems.
Did you find and correct the condition?

-

Go to Step 16

Go to Step 15

14

Replace the headlamp switch. Refer to
Headlamp Switch Replacement .
Did you complete the replacement?

-

Go to Step 16

-

15

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

IMPORTANT:

Perform the setup procedure for the body
control module (BCM).

-

Go to Step 16

-

16

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 ACCESSORIES & EQUIPMENT Lighting Systems - Hummer H2

DTC B2625

Circuit Description

The body control module (BCM) receives a variable voltage signal from the instrument panel (I/P) dimmer
switch requesting to illuminate the dimming lamps to a desired intensity. When this occurs, the BCM directly
sends a pulse width modulated (PWM) voltage based on the I/P dimmer switch position on the LED dimming
supply circuit, controls illumination lamps dimming control circuit, and the instrument panel lamps dimming
supply voltage circuit.

Voltage for the LED dimming supply circuit, controls illumination lamps dimming control circuit, and the
instrument panel lamps dimming supply voltage circuit is from the TBC 2 A fuse in the instrument panel (I/P)
fuse block directly through the BCM to these circuits.

Conditions for Running the DTC

The battery voltage must be between 9.0-16.0 volts.

Conditions for Setting the DTC

z

The controls illumination lamps dimming control circuit is shorted to ground.

z

The LED dimming supply circuit is shorted to ground.

z

There is a loss of the I/P fuse block TBC 2 A fuse battery supply voltage to the BCM for 1 second.

Action Taken When the DTC Sets

All dimming lamps will not illuminate or the control switch ON/OFF indicators will not illuminate.

Conditions for Clearing the MIL/DTC

z

This DTC will clear on current status after the condition for setting the fault is corrected.

z

A history DTC will clear after 100 consecutive ignition cycles without a fault present.

z

History and current DTC(s) can be cleared using a scan tool.

Diagnostic Aids

z

Perform a visual inspection for loose or poor connections at all related components. Refer to Testing for
Intermittent Conditions and Poor Connections in Wiring Systems.

z

A short to ground in the following circuits will cause the TBC 2 A fuse to open.

{

The controls illumination lamps dimming control.

{

Battery positive voltage from the I/P fuse block TBC 2 A fuse.

z

An open in the TBC 2 A fuse will cause the BCM to set the following DTC:

{

B0951

{

B2610

2004 Hummer H2

2004 ACCESSORIES & EQUIPMENT Lighting Systems - Hummer H2

{

B2625

Test Description

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

4: After replacement of the BCM you must calibrate the new module for proper operation.

DTC B2625

DTC B2645

Circuit Description

Step

Action

Yes

No

Schematic Reference:Interior Lights Dimming Schematics
Connector End View Reference:Lighting Systems Connector End Views or Body Control System
Connector End Views in Body Control System

1

Did you perform the Lighting System Diagnostic System Check?

Go to

Step 2

Go to Diagnostic

System Check -

Lighting Systems

2

Test the following circuits for a short to ground:

z

Controls illumination lamps dimming control

z

LED dimming supply

z

Battery positive voltage circuit of BCM from the TBC 2 A
fuse

Did you find and correct the condition?

Go to

Step 5

Go to Step 3

3

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 5

Go to Step 4

4

Replace the body control module (BCM). Refer to Body Control
Module Replacement in Body Control System.Did you complete
the replacement?

IMPORTANT:

Perform the setup procedure for the BCM.

Go to

Step 5

-

5

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 ACCESSORIES & EQUIPMENT Lighting Systems - Hummer H2

The body control module (BCM) monitors the ambient light sensor signal circuit in order to determine if the
daytime running lights (DRL) or the auto headlights (ALC) should be turned ON in the AUTO mode. When the
BCM senses the ambient light sensor signal voltage is between 1.75-4.9 volts, either the DRL will be
commanded ON or the ALC will be commanded ON depending upon the amount of light received by the
sensor.

Conditions for Running the DTC

The system voltage must be between 9.0-16.0 volts.

Conditions for Setting the DTC

z

When the ambient light sensor signal voltage is less than 1.75 volts.

z

When the ambient light sensor signal voltage is more than 4.9 volts.

Action Taken When the DTC Sets

The ALC will remain ON in any ambient light state.

Conditions for Clearing the MIL/DTC

z

This DTC will clear immediately after the condition for setting the fault is corrected.

z

A history DTC will clear after 100 consecutive ignition cycles without a fault present.

z

Use a scan tool in order to clear history and current DTCs.

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.

DTC B2645

Step

Action

Value

(s)

Yes

No

Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics
Connector End View Reference: Lighting Systems Connector End Views or Body Control System
Connector End Views in Body Control System

1

Did you perform the Lighting Systems
Diagnostic System Check?

-

Go to Step 2

Go to Diagnostic

System Check -

Lighting

Systems

1. Install a scan tool.

2004 Hummer H2

2004 ACCESSORIES & EQUIPMENT Lighting Systems - Hummer H2