Hummer H2. Manual - part 313

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 DTCs 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

An open circuit up to the first splice only, from the BCM, will set the DTC.  

z

A short to ground on the backup lamp supply voltage circuit, courtesy lamp supply voltage circuit OR the 
TBC 2B battery positive voltage circuit to the BCM will open the TBC 2B fuse in the left instrument 
panel fuse block.  

Test Description 

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

3: This step test determines if the problem exists in the wiring or the BCM.  

4: This step test determines if the problem exists in the wiring or the BCM.  

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

DTC B2615 

Step

Action

Yes

No

Schematic Reference: Interior Lights 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

Inspect the TBC 2B fuse in the instrument panel fuse block. 
Is the fuse open?

Go to 

Step 3

Go to Step 4

3

Test the following circuits for a short to ground. Refer to 
Circuit Testing and Wiring Repairs in Wiring Systems: 

z

Courtesy lamp supply voltage  

z

Backup lamp supply voltage  

z

TBC 2B battery positive voltage to the body control 
module (BCM)  

 
Did you find and correct the condition?

Go to 

Step 6

Go to Step 5

Test the courtesy lamp supply voltage circuit for the 
following conditions: 

z

An open  

 

2004 Hummer H2 

2004 ACCESSORIES & EQUIPMENT Lighting Systems - Hummer H2

  

DTC B2620 

Circuit Description 

The BCM directly sends a 5-volt reference voltage to the I/P dimmer switch which is then adjusted based on the 
I/P dimmer switch position and returned as a low reference and a signal to the BCM. The BCM uses this signal 
to directly control the desired level of instrument panel illumination lamp intensity. 

Conditions for Running the DTC 

The battery voltage must be between 9.0-16.0 volts. 

Conditions for Setting the DTC 

z

The BCM monitors a low reference voltage of less than 4.5 volts.  

z

The BCM monitors a high reference voltage of greater than 5.5 volts.  

z

The BCM monitors a signal voltage of equal or greater than 4.86 volts for more than 1 second.  

Action Taken When the DTC Sets 

The instrument panel illumination lamp dimming will not operate. 

Conditions for Clearing the MIL/DTC 

z

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

4

z

A short to voltage  

z

High resistance 

Refer to Circuit Testing and Wiring Repairs in 
Wiring Systems. 

 
Did you find and correct the condition?

Go to 

Step 6

Go to Step 5

5

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 BCM.

Go to 

Step 6

-

6

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

  

z

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

z

History and current DTCs can be cleared using a scan tool.  

Test Description 

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

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

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

5: Tests for a short to voltage in the 5-volt reference circuit.  

6: Tests for a high resistance or an open in the low reference circuit.  

DTC B2620 

Step

Action

Value

(s)

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 Systems 
Diagnostic System Check?

-

Go to Step 2

Go to 

Diagnostic 

System Check - 

Lighting 

Systems

2

1. Install a scan tool.  

2. Turn ON the ignition, with the engine 

OFF.  

3. With the scan tool, observe the Dimming 

Input data parameter in the Body Control 
Module Data List.  

Does the scan tool indicate that the Dimming 
Input data parameter is within the specified 
range?

4.5-

5.5 V

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 headlamp switch.  

3. Turn ON the ignition, with the engine 

OFF.  

4. With a scan tool, observe the Dimming 

Input data parameter.  

Does the scan tool indicate that the Dimming 
Input data parameter is less than the specified 

4.5 V

 

2004 Hummer H2 

2004 ACCESSORIES & EQUIPMENT Lighting Systems - Hummer H2

  

value?

Go to Step 4

Go to Step 10

4

1. Turn OFF the ignition.  

2. Connect a 3 amp fused jumper wire 

between the 5-volt reference circuit of the 
I/P dimmer/headlamp switch and the signal 
circuit of the I/P dimmer/headlamp switch. 

3. Turn ON the ignition, with the engine 

OFF.  

4. With a scan tool, observe the Dimming 

Input data parameter.  

Does the scan tool indicate that the Dimming 
Input data parameter is greater than the specified 
value?

4.86 

V

Go to Step 5

Go to Step 8

5

1. Disconnect the fused jumper wire.  

2. Measure the voltage between the 5-volt 

reference circuit of the I/P 
dimmer/headlamp switch and the low 
reference circuit of the I/P 
dimmer/headlamp switch.  

Does the voltage measure less than the specified 
value?

5.15 

V

Go to Step 6

Go to Step 7

6

1. Turn OFF the ignition.  

2. Disconnect the negative battery cable. 

Refer to Battery Negative Cable 
Disconnect/Connect Procedure (Single 
Battery) in Engine Electrical.  

3. Measure the resistance from the low 

reference circuit of the I/P 
dimmer/headlamp switch to a good ground. 

Does the resistance measure less than the 
specified value?

5 ohm

Go to Step 12

Go to Step 11

7

Test the 5-volt reference 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

8

Test the 5-volt reference 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 9

 

2004 Hummer H2 

2004 ACCESSORIES & EQUIPMENT Lighting Systems - Hummer H2