Hummer H3. Manual — part 1409

parameter.

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

Go to Step 10 Go to Step 4

4

1. Turn OFF the ignition.

2. Connect a 3-amp fused

jumper wire between the
connector terminals of the
low reference circuit and
the signal circuit of the
headlamp and panel
dimmer switch.

3. Turn ON the ignition,

with the engine OFF.

4. With a scan tool, observe

the Dimming
Potentiometer input data
parameter.

Does the scan tool indicate that
the Dimming Potentiometer
input data parameter is less
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 connector
terminals of the low
reference circuit and the
signal circuit of the
headlamp and panel
dimmer switch.

Does the voltage measure less
than the specified value?

5.15 V

Go to Step 6 Go to Step 7

1. Turn OFF the ignition.

2007 Hummer H3

2007 ACCESSORIES & EQUIPMENT Lighting - H3

6

2. Disconnect the negative

battery cable.

3. Measure the resistance

from the low reference
circuit of the headlamp
and panel dimmer switch
connector and a good
ground.

Does the resistance measure
less than the specified value?

5 ohms

Go to Step 12

Go to Step

11

7

Test the signal circuit of the
headlamp and panel dimmer
switch for a short to voltage.
Refer to Circuit Testing and
Wiring Repairs .
Did you find and correct the
condition?

-

Go to Step 16

Go to Step

13

8

Test the signal circuit of the
headlamp and panel dimmer
switch for a open or high
resistance. Refer to Circuit
Testing and Wiring Repairs .
Did you find and correct the
condition?

-

Go to Step 16 Go to Step 9

9

Test the low reference circuit
of the headlamp and panel
dimmer switch for an open or
high resistance. Refer to
Circuit Testing and Wiring
Repairs .
Did you find and correct the
condition?

-

Go to Step 16

Go to Step

13

10

Test the signal circuit of the
headlamp and panel dimmer
switch for a short to voltage.
Refer to Circuit Testing and
Wiring Repairs .
Did you find and correct the

-

Go to Step

2007 Hummer H3

2007 ACCESSORIES & EQUIPMENT Lighting - H3

condition?

Go to Step 16

13

11

1. Disconnect the body

control module.

2. Test the low reference

circuit of the headlamp
and panel dimmer switch
for a high resistance or an
open. Refer to Circuit
Testing and Wiring
Repairs .

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
headlamp and panel dimmer
switch. Refer to Circuit
Testing and Wiring Repairs .
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
BCM. Refer to Circuit
Testing and Wiring Repairs .
Did you find and correct the
condition?

-

Go to Step 16

Go to Step

15

14

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

-

Go to Step 16

-

15

Replace the BCM. Refer to
Control Module References
for replacement, setup and
programming.
Did you complete the
replacement?

-

Go to Step 16

-

2007 Hummer H3

2007 ACCESSORIES & EQUIPMENT Lighting - H3

DTC B2647 OR B2648

Circuit Description

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.

DTC Descriptors

This diagnostic procedure supports the following DTC:

DTC B2647 Ambient Light Sensor Circuit Low

DTC B2648 Ambient Light Sensor Circuit High

Conditions for Running the DTC

The system voltage must be between 9-16 volts.

Conditions for Setting the DTC

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

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

Action Taken When the DTC Sets

The ALC will remain always ON or always OFF in any ambient light state.

Conditions for Clearing the MIL/DTC

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

2007 Hummer H3

2007 ACCESSORIES & EQUIPMENT Lighting - H3