Hummer H3. Instruction - page 30

DTC B1390

Diagnostic Instructions

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

Review Strategy Based Diagnosis for an overview of the diagnostic approach.

Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC B1390

Device Voltage Reference Input 1 Circuit - GBCM RVC VSENSE B+

Diagnostic Fault Information

Typical Scan Tool Data

Battery Voltage Signal - GBCM

Circuit/System Description

The generator battery control module (GBCM) monitors the battery voltage for precision
electrical power management. The GBCM monitors both the RVC PWR B+ circuit and the RVC
VSENSE B+ circuit to precisely determine system voltage. If the RVC VSENSE B+ circuit is
1.5 volts less than the RVC PWR B+ circuit for 7 seconds, then DTC B1390 will set.

Conditions for Running the DTC

Circuit

Short to

Ground

Open/High

Resistance

Short to

Voltage

Signal

Performance

RVC PWR B+

-

-

-

-

RVC VSENSE B+

B1390

B1390

-

-

Ground

-

B1390

-

-

Circuit

Short to

Ground

Open

Short to Voltage

Operating Conditions: Ignition ON
Parameter Normal Value: 12.60 Volts
RVC PWR B+

12.60 Volts

12.60 Volts

12.60 Volts

RVC VSENSE B+

0.00 Volts

0.00 Volts

12.60 Volts

2008 Hummer H3

2008 ENGINE Engine Electrical - H3

This diagnostic runs every 100 ms.

Conditions for Setting the DTC

The RVC VSENSE B+ circuit is 1.5 volts less than the RVC PWR B+ circuit for 7 seconds

Action Taken When the DTC Sets

The GBCM will request the driver information center (DIC) to display the SERVICE
CHARGSYS message.

The GBCM uses the less accurate RVC PWR B+ circuit for voltage readings.

Conditions for Clearing the DTC

During the current ignition cycle, the difference between the less precision battery positive
voltage circuit reading and the high precision battery voltage sense circuit reading is less
than 1.5 volts.

The SERVICE CHARGSYS DIC message will turn off 7 seconds after the voltage on the
RVC VSENSE B+ circuit returns to normal.

Diagnostic Aids

Inspect the RVC PWR and RVC VSENSE fuses for opens.

Inspect ground G102. Verify that it is clean and tight.

Reference Information

Schematic Reference

Starting and Charging Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Charging System Description and Operation

Electrical Information Reference

Circuit Testing

2008 Hummer H3

2008 ENGINE Engine Electrical - H3

Connector Repairs

Testing for Intermittent Conditions and Poor Connections

Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

1. Engine running, accessories OFF, measure and record the battery voltage at the battery

terminals. The voltage should be between 12.6 and 15.0 volts.

If not within the specified range, refer to Charging System Test.

2. Observe the scan tool GBCM Battery Voltage Signal parameter. The reading should be

between 12.6 and 15.0 volts.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the GBCM.

2. Ignition OFF, test for less than 6.5 ohms between the ground circuit terminals listed below

and ground.

Terminal H

Terminal F

If greater than the specified range, test the ground circuit for an open/high resistance.

3. Verify that a test lamp illuminates between the B+ circuit terminals listed below and

ground.

Terminal A

Terminal C

If the test lamp does not illuminate, test the B+ circuit for a short to ground or an
open/high resistance.

4. If all circuits tests normal, replace the GBCM.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for GBCM replacement, setup, and programming

2008 Hummer H3

2008 ENGINE Engine Electrical - H3

DTC B1487

Diagnostic Instructions

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

Review Strategy Based Diagnosis for an overview of the diagnostic approach.

Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC B1487

Generator L-Terminal Circuit Low - Turn On Signal Circuit

Diagnostic Fault Information

Circuit/System Description

The generator battery control module (GBCM) controls the generator through the generator turn
on signal circuit, or L-Terminal 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 when the engine is
running is between 5-100 percent. If the generator turn on signal circuit is in the 0-5 percent
range, or pulled low to ground, then DTC B1487 will set.

Conditions for Running the DTC

The engine is running.

This diagnostic shall run every 100 ms.

Conditions for Setting the DTC

The generator turn on signal circuit is less than 5 percent duty cycle for 2 minutes.

Action Taken When the DTC Sets

The charge indicator illuminates on the instrument panel cluster (IPC).

The driver information center (DIC) displays the SERVICE CHARGSYS message.

Circuit

Short to

Ground

Open/High

Resistance

Short to

Voltage

Signal

Performance

Generator Turn On Signal

B1487

-

B1488

-

2008 Hummer H3

2008 ENGINE Engine Electrical - H3

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