Battery, Charging System & Starting System: Overview — Chevrolet Silverado 3500 HD (2007-2012)

Circuit/System Description

The control modules on this vehicle monitor the voltage on the battery positive (B+) voltage circuits. The following modules on this vehicle will set DTC B1325 if high or low battery voltage is detected

Audio amplifier
Instrument panel cluster (IPC)
Passenger presence system (PPS)
Radio
Rear object sensor control module

The theft deterrent module (TDM) monitors the battery positive (B+) voltage available to it. If the voltage at the TDM is between 6-9 volts, and the voltage being reported by a serial data message is greater than 9 volts, then DTC B1424 00 sets.

The battery current sensor is a 3-wire hall effect current sensor. The battery current sensor monitors the battery current. The signal circuit is an input to the body control module (BCM). The sensor creates a 5-volt pulse width modulation (PWM) signal of 128 Hz with a duty cycle of 0-100 percent. Normal duty cycle is between 4-96 percent. The signal circuit is an input to the body control module (BCM). If the duty cycle is outside of the normal range, DTC B1516 08 sets. The BCM also tests for correct polarity of the sensor. If the BCM detects positive current flow with the engine OFF, DTC B1516 66 sets.

The body control module (BCM) has 2 circuits for monitoring vehicle system voltage. The BCM B+ is supplied to terminal 3 X3 by the BCM fuse, and the high resolution B+ is supplied to the BCM terminal 10 X4 by the IPC fuse. The BCM monitors the system voltage on both circuits to ensure that the voltage stays within the proper range. Damage to components, and incorrect data may occur when the voltage is out of range. If the BCM detects the system voltage on the high resolution B+ circuit is outside the normal range, DTC B1517 will set.

The body control module (BCM) monitors the state of charge (SOC) of the electrical system. If the BCM senses that the current draw was greater than 2 amps and the SOC at key-on is 30 percent lower than it was when the engine was last running, DTC B1527 00 will set.

The trailer brake control module (TBCM) monitors the 12V system voltage to make sure that the voltage stays within the proper range. Damage to components, and incorrect data can occur when the voltage is out of range. The TBCM monitors the system voltage. If the TBCM detects a 12V system voltage outside an expected range, DTC C0800 will set.

The electronic brake control module (EBCM) monitors the battery positive (B+) voltage level available for system operation. A low voltage condition prevents the system from operating properly. If low voltage is detected by the EBCM, then DTC C0899 sets.

The electronic brake control module (EBCM) monitors the battery positive (B+) voltage. If the voltage level is too high, damage may result in the system. When a high voltage condition is detected, DTC C0900 00 sets.

Circuit/System Description (ECM)

The engine control module (ECM) monitors the system voltage to ensure that the voltage stays within the proper range. Damage to components, and incorrect data may occur when the voltage is out of range.

Circuit/System Description (FPCM)

The fuel pump control module (FPCM) monitors the system voltage to ensure that the voltage stays within the proper range. Damage to components, and incorrect data may occur when the voltage is out of range.

Circuit/System Description (Gasoline)

When the ignition switch is placed in the start position, a discrete signal is supplied to the body control module (BCM) notifying it that the ignition is in the start position. The BCM then sends a message to the engine control module (ECM) that crank has been requested. The ECM then verifies that the clutch is pressed for the manual transmission or that the automatic transmission is in park or neutral, and that the immobilizer is not disabling engine starting. If conditions are acceptable for cranking, then the ECM supplies 12 V to the control circuit of the STRTR relay. When this occurs, battery voltage is supplied through the switch of the STRTR relay to terminal S X2 of the starter solenoid, and the engine cranks. The ECM monitors the voltage on the STRTR relay control circuit.

Circuit/System Description (Diesel)

When the ignition switch is placed in the start position, a discrete signal is supplied to the body control module (BCM) notifying it that the ignition is in the start position. The BCM then sends a message to the engine control module (ECM) that crank has been requested. The ECM then verifies that the clutch is pressed for the manual transmission or that the automatic transmission is in Park or Neutral, and that the immobilizer is not disabling engine starting. If conditions are acceptable for cranking, then the ECM supplies 12 V to the control circuit of the STRTR relay. When this occurs, battery voltage is supplied through the switch of the STRTR relay to terminal S X2 of the starter solenoid, and the engine cranks. The ECM monitors the voltage on the STRTR relay control circuit.

The engine control module (ECM) uses the charge indicator signal circuit, or L-terminal circuit, to control the load of the generator on the engine. A high side driver in the ECM applies a voltage to the voltage regulator. This signals the voltage regulator to turn the field circuit ON and OFF. The ECM monitors the state of the charge indicator signal circuit.

The engine control module (ECM) uses the generator field duty cycle signal circuit, or F-terminal circuit, to monitor the duty cycle of the generator. The generator field duty cycle signal circuit connects to high side of the field windings in the generator. A pulse width modulated (PWM) high side driver in the voltage regulator turns the field windings ON and OFF. The ECM uses the PWM signal input to determine the generator load on the engine. This allows the ECM to adjust the idle speed to compensate for high electrical loads. The ECM monitors the status of the generator field duty cycle signal circuit. When the ignition is ON and the engine is OFF, the ECM should detect a duty cycle near 0 percent. When the engine is running, the duty cycle should be between 5-99 percent.

The engine control module (ECM) controls engine cranking based on a power mode input and the status of the park/neutral position (PNP) switch or clutch pedal position sensor. With the transmission in Park/Neutral, voltage at the ECM PNP switch signal circuit is low. This indicates to the ECM that conditions are acceptable for cranking. When a power mode crank request is seen, the ECM applies voltage to the starter relay control circuit. This energizes the coil side of the relay, which pulls the switch side of the relay closed, applying voltage to the starter terminal S X2 and engaging the starter solenoid.

When the ignition switch is placed in the START position, a discrete signal is supplied to the body control module (BCM) notifying it that the ignition is in the START position. The BCM then sends a serial data message to the engine control module (ECM) that crank has been requested. The ECM monitors the park/neutral position switch and the clutch pedal position sensor. If the transmission is in Park or Neutral, or the clutch pedal is pressed, and there are no DTCs that inhibit engine starting, then the ECM supplies voltage to the control circuit of the STRTR relay. When this occurs, battery voltage is supplied through the STRTR relay to the X2-S terminal of the starter solenoid. The starter solenoid energizes, and supplies battery voltage to the starter from the B terminal to crank the engine.

The PG starter motors are non-repairable. They have pole pieces that are arranged around the armature. Both solenoid windings are energized. The pull-in winding circuit is completed to the ground through the starter motor. The windings work together magnetically to pull and hold in the plunger. The plunger moves the shift lever. This action causes the starter drive assembly to rotate on the armature shaft spline as it engages with the flywheel ring gear on the engine. Moving at the same time, the plunger also closes the solenoid switch contacts in the starter solenoid. Full battery voltage is applied directly to the starter motor and it cranks the engine.

Electrical Power Management (EPM) Overview

The electrical power management (EPM) system is designed to monitor and control the charging system and send diagnostic messages to alert the driver of possible problems with the battery and generator. This EPM system primarily utilizes existing on-board computer capability to maximize the effectiveness of the generator, to manage the load, improve battery state-of-charge and life, and minimize the system's impact on fuel economy. The EPM system performs 3 functions

It monitors the battery voltage and estimates the battery condition.
It takes corrective actions by boosting idle speeds, and adjusting the regulated voltage.
It performs diagnostics and driver notification.

The battery condition is estimated during ignition-off and during ignition-on. During ignition-off the state-of-charge (SOC) of the battery is determined by measuring the open-circuit voltage. The SOC is a function of the acid concentration and the internal resistance of the battery, and is estimated by reading the battery open circuit voltage when the battery has been at rest for several hours.

The SOC can be used as a diagnostic tool to tell the customer or the dealer the condition of the battery. Throughout ignition-on, the algorithm continuously estimates SOC based on adjusted net amp hours, battery capacity, initial SOC, and temperature.

While running, the battery degree of discharge is primarily determined by a battery current sensor, which is integrated to obtain net amp hours.

In addition, the EPM function is designed to perform regulated voltage control (RVC) to improve battery SOC, battery life, and fuel economy. This is accomplished by using knowledge of the battery SOC and temperature to set the charging voltage to an optimum battery voltage level for recharging without detriment to battery life.

The Charging System Description and Operation is divided into 3 sections. The first section describes the charging system components and their integration into the EPM. The second section describes charging system operation. The third section describes the instrument panel cluster (IPC) operation of the charge indicator, driver information center (DIC) messages, and voltmeter operation.

Charging System Operation

The purpose of the charging system is to maintain the battery charge and vehicle loads. There are 6 modes of operation and they include

Battery Sulfation Mode
Charge Mode
Fuel Economy Mode
Headlamp Mode
Start Up Mode
Voltage Reduction Mode

The engine control module (ECM) controls the generator through the generator turn on signal. It monitors the generator performance though the generator field duty cycle 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. Between 0-5 percent and 95-100 percent are for diagnostic purposes. The following table shows the commanded duty cycle and output voltage of the generator

Commanded Duty Cycle	Generator Output Voltage
10%	11 V
20%	11.56 V
30%	12.12 V
40%	12.68 V
50%	13.25 V
60%	13.81 V
70%	14.37 V
80%	14.94 V
90%	15.5 V

The generator provides a feedback signal of the generator voltage output through the generator field duty cycle signal circuit to the ECM. This information is sent to the body control module (BCM). The signal is a 5 volt PWM signal of 128 Hz with a duty cycle of 0-100 percent. Normal duty cycle is between 5-99 percent. Between 0-5 percent and 100 percent are for diagnostic purposes.

Charge Indicator Operation

The instrument panel cluster (IPC) illuminates the charge indicator and displays a warning message in the driver information center (DIC) when the one or more of the following occurs

The engine control module (ECM) detects that the generator output is less than 11 volts or greater than 16 volts. The IPC receives a GMLAN message from the ECM requesting illumination.
The BCM determines that the system voltage is less than 11 volts or greater than 16 volts.
The IPC receives a GMLAN message from the body control module (BCM) indicating there is a system voltage range concern.
The IPC performs the displays test at the start of each ignition cycle. The indicator illuminates for approximately 3 seconds.
The ignition is ON, with the engine OFF.

Battery Voltage Gauge Operation

The IPC displays the system voltage as received from the BCM over the GMLAN serial data circuit. If there is no communication with the BCM then the gauge will indicate minimum.

This vehicle is equipped with a regulated voltage control (RVC) system. This system turns off the generator when it is not required in order to improve fuel economy. The generator will turn back on when additional voltage is required. This will cause the voltmeter to fluctuate between 12 and 14 volts as opposed to non-regulated systems which usually maintain a more consistent reading of 14 volts. This fluctuation with the RVC system is normal system operation and NO repairs should be attempted.

Starting System Description and Operation

The starter motors are non-repairable starter motors. They have pole pieces that are arranged around the armature. Both solenoid windings are energized. The pull-in winding circuit is completed to the ground through the starter motor. The windings work together magnetically to pull and hold in the plunger. The plunger moves the shift lever. This action causes the starter drive assembly to rotate on the armature shaft spline as it engages with the flywheel ring gear on the engine. Moving at the same time, the plunger also closes the solenoid switch contacts in the starter solenoid. Full battery voltage is applied directly to the starter motor and it cranks the engine.

As soon as the solenoid switch contacts close, current stops flowing thorough the pull-in winding because battery voltage is applied to both ends of the windings. The hold-in winding remains energized. Its magnetic field is strong enough to hold the plunger, shift lever, starter drive assembly, and solenoid switch contacts in place to continue cranking the engine. When the engine starts, pinion overrun protects the armature from excessive speed until the switch is opened.

When the ignition switch is released from the START position, the START relay opens and battery voltage is removed from the starter solenoid S terminal. Current flows from the motor contacts through both windings to the ground at the end of the hold-in winding. However, the direction of the current flow through the pull-in winding is now opposite the direction of the current flow when the winding was first energized.

The magnetic fields of the pull-in and hold-in windings now oppose one another. This action of the windings, along with the help of the return spring, causes the starter drive assembly to disengage and the solenoid switch contacts to open simultaneously. As soon as the contacts open, the starter circuit is turned off.

Battery, Charging System & Starting System: Overview Chevrolet Silverado 3500 HD