Hummer H3. Manual — part 1126

DTC B1488

Circuit Description

The generator battery control module controls the generator through the generator turn on signal
circuit. The signal is a 5-volt pulse width modulation (PWM) signal of 128 Hz with a duty cycle
of 0-100 percent. Normal duty cycle is between 5-95 percent. If the generator turn on signal
circuit is 65 percent or greater duty cycle or pulled high to battery positive voltage, 5 volts, then
DTC B1488 will set.

DTC Descriptor

Is the DMM reading equal to the
specified value?

Go to Step 4 Go to Step 3

3

Inspect for poor connections at the
harness connector of the generator
battery control module. Refer to
Testing for Intermittent
Conditions and Poor Connections
and Connector Repairs .
Did you find and correct the
condition?

-

Go to Step 6 Go to Step 5

4

Repair the short to ground of the
generator turn on signal circuit.
Did you find and correct the
condition?

-

Go to Step 6 Go to Step 5

5

Replace the generator battery control
module. Refer to Control Module
References for replacement, setup
and programming.
Did you complete the replacement?

-

Go to Step 6

-

6

1. Use the scan tool in order to

clear the DTC.

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 ENGINE Engine Electrical - H3

This diagnostic procedure supports the following DTC:

DTC B1488 Generator L-Terminal Circuit High

Conditions for Running the DTC

Vehicle in RUN mode and Engine Run Flag is False.

The engine RPM is less than or equal to 0 RPM.

This diagnostic shall be run every 100 ms.

Conditions for Setting the DTC

The generator turn on signal circuit is 65 percent or greater and shorted high to battery voltage, 5
volts, for greater than 5 seconds.

Action Taken When the DTC Sets

The generator battery control module will request the driver information center (DIC) message of
Service Charging System and commands ON the Battery indicator.

Conditions for Clearing the DTC

The generator battery control module determines the fault has cleared.

Diagnostic Aids

Recommended Action:

Correct L-Term short high condition.

Clear the codes.

Cycle the ignition.

If a fault condition persists, replace the module.

IMPORTANT: You must cycle the ignition after clearing the DTC to turn OFF the

DIC message of Service Charging System.

IMPORTANT: You must cycle the ignition after clearing the DTC to turn OFF the

DIC message of Service Charging System and turn OFF the
battery indicator.

2007 Hummer H3

2007 ENGINE Engine Electrical - H3

DTC B1488

Step

Action

Values

Yes

No

Schematic Reference: Starting and Charging Schematics
Connector End View Reference: Engine Electrical Connector End Views

1

Did you perform the Diagnostic
System Check - Vehicle?

-

Go to Step 2

Go to
Diagnostic
System
Check -
Vehicle

2

1. Ignition ON, engine OFF.

2. With a DMM, test the generator

turn on signal circuit of the
generator battery control
module.

Is the DMM reading equal to or
above the specified value?

4.8 - 5.2 V

Go to Step 4 Go to Step 3

3

Inspect for poor connections at the
harness connector of the generator
battery control module. Refer to
Testing for Intermittent
Conditions and Poor Connections
and Connector Repairs .
Did you find and correct the
condition?

-

Go to Step 6 Go to Step 5

4

Repair the short to battery of the
generator turn on signal circuit.
Did you find and correct the
condition?

-

Go to Step 6 Go to Step 5

5

Replace the generator battery control
module. Refer to Control Module
References for replacement, setup
and programming.
Did you complete the replacement?

-

Go to Step 6

-

1. Use the scan tool in order to

clear the DTC.

2. Operate the vehicle within the

Conditions for Running the

2007 Hummer H3

2007 ENGINE Engine Electrical - H3

DTC B1492

Circuit Description

The generator battery control module monitors the generator through the generator field duty
cycle signal circuit. The signal is a pulse width modulation (PWM) signal of 128 Hz with a duty
cycle of 0-100 percent. Normal duty cycle is between 5-95 percent. If the generator field duty
cycle signal circuit is in the 0-5 percent range or pulled low to ground, then DTC B1492 will set.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B1492 Generator F-Terminal Circuit Low

Conditions for Running the DTC

Vehicle in RUN mode and Engine Run Flag is True.

The engine speed is less that 1,000 RPM.

DTC B1487 or B1488 is not set as a current DTC.

This diagnostic shall be run every 100 ms.

Conditions for Setting the DTC

The generator field duty cycle signal circuit is less than or equal to 5 percent duty cycle for more
than 120 seconds.

Action Taken When the DTC Sets

The generator battery control module will request the driver information center (DIC) message of
Service Charging System and commands ON the Battery indicator.

Conditions for Clearing the DTC

The generator field duty cycle signal circuit input is greater than 5 percent duty cycle.

Clear the DTC with a scan tool.

6

DTC, as specified in the
supporting text.

Does the DTC reset?

-

Go to Step 2 System OK

2007 Hummer H3

2007 ENGINE Engine Electrical - H3