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