Hybrid Engine Electrical System (HP2): Other Chevrolet Silverado 3500 HD

Battery Usage

Scheme 15

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for the appropriate module replacement, setup, and programming.

Reference Information

Schematic Reference

1. «Immobilizer Schematics»(ref-317200-S20776359602009060900000)
2. «Starting and Charging Schematics»(ref-317183-S04519712352009060900000)
3. «Power Distribution Schematics»(ref-317157-S33271324242009060900000)
4. «Ground Distribution Schematics»(ref-317157-S38941303322009060900000)

Connector End View Reference

Component Connector End Views

Description and Operation

1. «Immobilizer Description and Operation»(ref-317200-S34447529552009060900000)
2. «Charging System Description and Operation»(ref-317183-S25211793842009060900000)

Electrical Information Reference

1. «Circuit Testing»(ref-317172-S12100958872009060900000)
2. «Connector Repairs»(ref-317172-S41839496312009060900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-317172-S08096213032009060900000)
4. «Wiring Repairs»(ref-317172-S40815672902009060900000)

Scan Tool Reference

Control Module References for scan tool information

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for TDM replacement, set up, and programming.

Circuit/System Verification

Ignition ON, headlamps and all accessories OFF, observe the scan tool BCM Battery Current parameter. The reading should be between -5 amps and -25 amps, and change with the amount of current draw on the battery.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Battery Current Sensor Replacement»(ref-317183-S22819733082009060900000)
2. «Control Module References»(ref-317173-S10180079792009060900000) for BCM replacement, setup, and programming

Schematic Reference

1. «Body Control System Schematics»(ref-317152-S33865031622009060900000)
2. «Power Distribution Schematics»(ref-317157-S33271324242009060900000)
3. «Ground Distribution Schematics»(ref-317157-S38941303322009060900000)

Connector End View Reference

Component Connector End Views

Description and Operation

Charging System Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-317172-S12100958872009060900000)
2. «Connector Repairs»(ref-317172-S41839496312009060900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-317172-S08096213032009060900000)
4. «Wiring Repairs»(ref-317172-S40815672902009060900000)

Scan Tool Reference

Control Module References for scan tool information

1. Engine running, accessories OFF, measure and record the battery voltage at the 12V battery terminals. The voltage should be between 12.6 and 15.0 volts. If not within the specified range, refer to «Charging System Test»(ref-317183-S41819932652009060900000) .
2. Observe the scan tool BCM Battery Voltage parameter and the Batt. Voltage High Res. parameter. Both readings should be between 12.60 and 15.00 volts.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for BCM replacement, setup, and programming.

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

1. «Circuit Testing»(ref-317172-S12100958872009060900000)
2. «Connector Repairs»(ref-317172-S41839496312009060900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-317172-S08096213032009060900000)
4. «Wiring Repairs»(ref-317172-S40815672902009060900000)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, compare the scan tool BCM Prev. State of Charge and Start Up State of Charge parameters. The scan tool readings should not differ by greater than 30 percent.

1. If the readings differ by greater than 30 percent, refer to «Battery Electrical Drain/Parasitic Load Test»(ref-317183-S40234149632009060900000) .

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. Engine running, accessories OFF, measure and record the battery voltage at the 12V battery terminals. The voltage should be between 12.6 and 15.0 volts. If not within the specified range, refer to «Charging System Test»(ref-317183-S41819932652009060900000) .
2. Observe the scan tool PSCM Battery Voltage parameter. The reading should be between 12.60 and 15.00 volts.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for PSCM replacement, setup, and programming.

1. Verify that there are no DTCs in the APM that disable the 42 Volt circuit, no engine-stall DTCs in the ECM, and no U-codes in any module. If there are any of the specified DTCs, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(ref-317170-S26882385112009060900000) .
2. 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»(ref-317183-S41819932652009060900000) .
3. Engine running, observe the scan tool PSCM Intermediate Voltage parameter. The voltage should be 37.5 - 50 Volts. If not within the specified range, refer to «Voltage Out Of Range At All Times»(ref-317183-S34135112382009080400000) .
4. Engine running, rotate the steering wheel left and right while stationary. Observe the scan tool PSCM Intermediate Voltage parameter. The voltage should remain greater than 37.5 Volts. If the voltage is less than the specified range only when turning the steering wheel, refer to «Low Voltage When Turning»(ref-317183-S02240361352009080400000) .
5. Operate the vehicle on a bumpy road. Observe the scan tool APM 42V Circuit Maximum parameter. The scan tool 42V Circuit Maximum parameter should be less than 50 Volts. If the voltage is greater than the specified range, replace the PSCM.

Voltage Out Of Range At All Times

1. Ignition OFF, disconnect the 42V harness connector X2 at the APM.
2. Ignition OFF and scan tool disconnected, open and close the driver door, and wait 1 minute. Test for less than 3 ohms between the ground circuit terminal 1 X2 of the APM and ground. If greater than the specified range, test the APM ground circuits for an open/high resistance. If the circuits test normal, replace the APM.
3. Ignition OFF, connect a DMM between the 42V+ circuit terminal 2 X2 of the APM and ground.
4. Ignition ON, command the APM Intermediate Voltage Control ON with a scan tool. Test for 37.5 - 60 volts between the 42V+ circuit terminal 2 X2 terminal and ground. Command the APM Intermediate Voltage Control OFF after completing this test. If not within the specified range, replace the APM.
5. Ignition OFF, verify that the 42V harness connector X2 is connected under the PSCM. If the connector is not connected, connect the connector.
6. If all circuits test normal, replace the PSCM.

Low Voltage When Turning

1. Inspect the steering system for mechanical binding. The steering should have a heavy feel, if the power steering is disabled, but should not bind. If there is any mechanical binding in the steering system, refer to «Steering Effort Hard in One or Both Directions (Standard)»(ref-317190-S16719303482009060900000) or «Steering Effort Hard in One or Both Directions (Two-Mode)»(ref-317190-S12145597922009060900000) .
2. If all circuits test normal, replace the power steering motor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Power Steering Assist Motor Replacement»(ref-317190-S05210262472009060900000)
2. «Control Module References»(ref-317173-S10180079792009060900000) for APM or PSCM replacement, setup and programming.

Schematic Reference

Antilock Brake System Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

ABS Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-317172-S12100958872009060900000)
2. «Connector Repairs»(ref-317172-S41839496312009060900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-317172-S08096213032009060900000)
4. «Wiring Repairs»(ref-317172-S40815672902009060900000)

Scan Tool Reference

Control Module References for scan tool information

1. Engine running, accessories OFF, measure and record the battery voltage at the 12 V battery terminals. The voltage should be between 12.6-15.0 V. If not within the specified range, refer to «Charging System Test»(ref-317183-S41819932652009060900000) .
2. Observe the scan tool EBCM Battery Voltage Signal parameter. The reading should be between 12.6-15.0 Volts.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for EBCM replacement, setup, and programming.

Schematic Reference

Antilock Brake System Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

ABS Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-317172-S12100958872009060900000)
2. «Connector Repairs»(ref-317172-S41839496312009060900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-317172-S08096213032009060900000)
4. «Wiring Repairs»(ref-317172-S40815672902009060900000)

Scan Tool Reference

Control Module References for scan tool information

1. Engine running, accessories OFF, measure and record the battery voltage at the 12 V battery terminals. The voltage should be between 12.6-15.0 V. If not within the specified range, refer to «Charging System Test»(ref-317183-S41819932652009060900000) .
2. Observe the scan tool EBCM Battery Voltage parameter. The reading should be between 12.6-15.0 Volts. If greater than the specified range, replace the EBCM.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for EBCM replacement, setup, and programming.

Schematic Reference

1. «Control Module References»(ref-317173-S10180079792009060900000) for ECM schematics
2. «Starting and Charging Schematics»(ref-317183-S04519712352009060900000)
3. «Power Distribution Schematics»(ref-317157-S33271324242009060900000)
4. «Ground Distribution Schematics»(ref-317157-S38941303322009060900000)

Connector End View Reference

Component Connector End Views

Description and Operation

Charging System Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-317172-S12100958872009060900000)
2. «Connector Repairs»(ref-317172-S41839496312009060900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-317172-S08096213032009060900000)
4. «Wiring Repairs»(ref-317172-S40815672902009060900000)

Scan Tool Reference

Control Module References for scan tool information

1. Engine running, accessories OFF, measure and record the battery voltage at the 12V battery terminals. The voltage should be between 12.6 and 15.0 V. If not within the specified range, refer to «Charging System Test»(ref-317183-S41819932652009060900000) .
2. Observe the scan tool ECM Ignition 1 Signal parameter. The reading should be between 12.6 and 15.0 V.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for ECM replacement, setup, and programming.

Electrical Information Reference

1. «Circuit Testing»(ref-317172-S12100958872009060900000)
2. «Connector Repairs»(ref-317172-S41839496312009060900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-317172-S08096213032009060900000)
4. «Wiring Repairs»(ref-317172-S40815672902009060900000)

1. Engine running, accessories OFF, measure and record the battery voltage at the 12V battery terminals. The voltage should be between 12.6 and 15.0 V. If not within the specified range, refer to «Charging System Test»(ref-317183-S41819932652009060900000) .
2. Observe the scan tool ECM Ignition 1 Signal parameter. The reading should be between 12.6 and 15.0 V. If greater than the specified range, replace the ECM.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for ECM replacement, setup, and programming.

Schematic Reference

1. «HVAC Schematics»(ref-317150-S21963128862009060900000)
2. «Hybrid Controls Schematics»(ref-317195-S21877844302009060900000)

Connector End View Reference

Component Connector End Views

Description and Operation

1. «Heating and Air Conditioning System Description and Operation (HP2)»(ref-317146-S16687303902009060900000)
2. «High Voltage Monitoring Systems Description»(ref-317195-S37622463922009060900000)

Electrical Information Reference

1. «Circuit Testing»(ref-317172-S12100958872009060900000)
2. «Connector Repairs»(ref-317172-S41839496312009060900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-317172-S08096213032009060900000)
4. «Wiring Repairs»(ref-317172-S40815672902009060900000)

Scan Tool Reference

Control Module References for scan tool information

Special Tools

EL-48900 HEV Safety Kit. See Special Tools .

1. Verify that no hybrid powertrain control module (HPCM) or engine control module (ECM) DTCs are set that indicate generator, HPCM, or battery failure, or that disable the high voltage. If the specified DTCs are set, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(ref-317170-S26882385112009060900000) .
2. Engine cranking, observe the scan tool accessory DC power control module (APM) HPCM 300V Circuit parameter. The reading should be between 225 Volts and 380 Volts. If not within the specified range, refer to «Jump Assist»(ref-317196-S00326282652009060900000) .
3. Ignition ON, observe the scan tool ACCM High Battery Voltage parameter. The reading should be between 225 Volts and 380 Volts.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for ACCM replacement, setup, and programming

Schematic Reference

1. «HVAC Schematics»(ref-317150-S21963128862009060900000)
2. «Hybrid Controls Schematics»(ref-317195-S21877844302009060900000)

Connector End View Reference

Component Connector End Views

Description and Operation

1. «Heating and Air Conditioning System Description and Operation (HP2)»(ref-317146-S16687303902009060900000)
2. «High Voltage Monitoring Systems Description»(ref-317195-S37622463922009060900000)

Electrical Information Reference

1. «Circuit Testing»(ref-317172-S12100958872009060900000)
2. «Connector Repairs»(ref-317172-S41839496312009060900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-317172-S08096213032009060900000)
4. «Wiring Repairs»(ref-317172-S40815672902009060900000)

Scan Tool Reference

Control Module References for scan tool information

1. Verify that no hybrid powertrain control module (HPCM) DTCs are set due to high battery voltage. If the specified DTCs are set, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(ref-317170-S26882385112009060900000) .
2. Engine running, observe the scan tool ACCM High Battery Voltage parameter. The reading should be between 225 Volts and 380 Volts. If greater than the specified range, replace the ACCM.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for ACCM replacement, setup, and programming.

Symptoms - Engine Electrical

The following steps must be completed before using the symptom tables.

1. Perform «Diagnostic System Check - Vehicle»(ref-317170-S03444519162009060900000) before using the Symptom Tables in order to verify that all of the following are true: The power modes are correct. The control modules can communicate via the serial data link. There are no DTCs set.
2. Review the system descriptions and operations in order to familiarize yourself with the system functions. Refer to one of the following system operations: «Battery Description and Operation»(ref-317183-S13621858572009060900000) «Charging System Description and Operation»(ref-317183-S25211793842009060900000) «Starting System Description and Operation»(ref-317183-S35552391192009060900000)

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections .

12-Volt Battery

The following procedure is for the 12-Volt battery only.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Battery Positive Cable Replacement (With LU3)»(ref-317151-S03102981872009060900000) or «Battery Positive Cable Replacement (With V8 Engine)»(ref-317151-S39545364752009060900000) or «Battery Positive Cable Replacement (With LMM)»(ref-317151-S03020482612009060900000)
2. «Battery Negative Cable Replacement (With LU3)»(ref-317151-S17497753032009060900000) or «Battery Negative Cable Replacement (With V8 Engine)»(ref-317151-S41898449832009060900000) or «Battery Negative Cable Replacement (With LMM)»(ref-317151-S09816463662009060900000)
3. «Battery Replacement»(ref-317151-S20126381222009060900000)

The following procedure is for the 12-volt battery only.

For information about charging the high voltage drive motor batteries, refer to Jump Assist Description and Operation .

Battery State of Charge

Note. Using voltage to determine the 12V batteries state of charge (SOC) is only accurate after the battery has been at rest for 24 hours. This is enough time for the acid in each cell to equalize. If the battery has been charged or discharged in the past 24 hours, the battery SOC will only be an estimate.

The maintenance-free batteries SOC is estimated by reading the voltage of the battery across the battery terminals. Because the voltage is affected by current flow into or out of the battery, the engine must be stopped and all electrical loads turned OFF, including parasitic loads, when checking the voltage. The voltage can also be affected if the battery has just been charged or discharged, so it is important to consider what has happened to the battery in the time just before testing. Use the following procedure to determine the batteries SOC

1. Be sure all electrical loads are turned OFF.
2. Determine whether the 12V battery has been used in a vehicle or charged within the past 12 hours. If the answer is no, the terminal voltage will be stabilized and no action is necessary before reading the voltage. Skip to step 3. If the answer is yes, terminal voltage will not be stabilized and you should wait 12 hours since the last time the battery was used.
3. Estimate the battery temperature by determining the average temperature to which the battery has been exposed for the past 12 hours.
4. Measure the battery voltage at the battery terminals. Refer to the following table to determine the SOC according to the estimated battery temperature

Use the SOC information as follows

1. A battery with a SOC that is below 65 percent must always be recharged before returning it to service or continuing storage.
2. A battery with a SOC that is 65 percent or greater is generally considered to be charged enough in order to be returned to normal service or in order to continue storage. However, if the 12V battery is being used in slow traffic or with short drive times, or if the temperature is very hot or very cold, the battery should be fully charged, to at least 90 percent, before returning it to service or continuing storage.

Charging Time Required

The time required to charge a 12V battery will vary depending upon the following factors

1. The battery charger capacity-The higher the charger amperage, the less time it will take to charge the battery.
2. The SOC of the 12V battery-A completely discharged battery requires more than twice as much charging time as a half charged battery. In a discharged battery with a voltage below 11 volts, the battery has a very high internal resistance and may only accept a very low current at first. Later, as the charging current causes the acid content to increase in the electrolyte, the charging current will increase. Extremely discharged batteries may not activate the reversed voltage protection in some chargers. Refer to the manufacturer's instructions for operating this circuitry.
3. The temperature of the battery-The colder the battery is, the more time it takes to recharge the battery. The charging current accepted by a cold battery is very low at first. As the battery warms, the charging current will increase.

Charging Procedure

Use the following procedure to charge the battery

1. Turn OFF the charger.
2. Ensure that all of the 12V battery terminal connections are clean and tight.
3. Connect the charger positive lead to the battery positive terminal on the battery.
4. Connect the negative charger lead to a solid engine ground in the engine compartment. If the negative battery cable is disconnected, connect directly to the battery.
5. Turn ON the charger and set to the highest setting for normal charging.
6. Inspect the battery every half hour after starting the battery charger. Charge the battery until the taper-rate charger indicates that the battery is fully charged. Estimate the battery temperature by feeling the side of the battery. If it feels hot to the touch or its temperature is over 45°C (125°F), discontinue charging and allow the battery to cool before resuming charging.
7. After charging, test the 12V battery. Refer to «Battery Inspection/Test»(ref-317151-S16908516992009060900000) .

The following procedure is for the 12-volt battery only.

The following information is for the 12-Volt battery only.

A battery is not designed to last forever. With proper care, however, the battery will provide years of good service. If the 12V battery tests good but still fails to perform well, the following are some of the more common causes

1. A vehicle accessory was left on overnight.
2. The driving speeds have been slow with frequent stops with many electrical accessories in use, particularly headlights, wipers, heated rear window, cellular telephone, etc.
3. The electrical load has exceeded the charging system output, particularly with the addition of aftermarket equipment.
4. Existing conditions in the 12V charging system.
5. The battery has not been properly maintained, including a loose battery hold down or missing battery insulator if used.
6. There are mechanical conditions in the electrical system, such as a short or a pinched wire, attributing to power failure. Refer to «General Electrical Diagnosis»(ref-317172-S16311420822009060900000) .

Electrolyte Freezing

The freezing point of electrolyte depends on its specific gravity. A fully charged 12V battery will not freeze until the ambient temperature gets below -54°C (-65°F). However, a battery with a low state of charge may freeze at temperatures as high as -7°C (+20°F). Since freezing may ruin a battery, the battery should be protected against freezing by keeping it properly charged. As long as the green eye is visible in the hydrometer, the freezing point of the battery will be somewhere below -32°C (-25°F).

Battery Protection During Vehicle Storage

Certain devices on the vehicle maintain a small continuous current drain on the battery. A battery that is not used for an extended period of time will discharge. Eventually permanent damage will result. Discharged batteries will also freeze in cold weather. Refer to Battery Inspection/Test .

In order to maintain a battery state of charge while storing the vehicle for more than 30 days, disconnect the battery ground to protect the battery from discharge by parasitic current drains.

When the battery cannot be disconnected

1. Maintain a high state of charge.
2. Establish a regular schedule for recharging the battery every 20-45 days.

A battery that has remained in a discharged state for a long period of time is difficult to recharge or may be permanently damaged.

Disconnect Procedure

Note. Do NOT disconnect the negative battery cable from the battery until a period of at least 1 minute after performing the following: Turning the ignition to OFF, without pausing at ACCESSORY, and without applying the brake pedal. These steps are necessary to allow the brake system pressure relief procedure to occur. Failure to follow these steps may result in warning lamps and/or DTCs being set pertaining to interruption of the pressure relief procedure. Other vehicle systems may also be affected by not allowing a 1 minute duration for power-down.

1. Turn off all lamps and accessories.
2. Turn the ignition OFF without pausing at ACCESSORY, and remove the ignition key.
3. Wait for at least 1 minute before disconnecting the negative battery cable from the battery, to allow for proper power-down procedures of certain vehicle systems.
4. Reposition the negative battery cable insulating cover (5) from the negative battery terminal.
5. Rotate the lever lock (4) counterclockwise in order to disconnect the negative battery cable from the battery.

Connect Procedure

Note. Clean any existing corrosion from the battery terminal and the battery cable.

1. Install the negative battery cable (6) to the battery.
2. Rotate the lever lock (4) clockwise until an audible click is heard in order to connect the negative battery cable to the battery.
3. Position the negative battery cable insulating cover (5) over the negative terminal.

300-Volt Battery

For information about the 300V hybrid drive motor battery, refer to Drive Motor Battery System Description .

Scheme 16

Note. Because of the materials used in the manufacture of automotive lead-acid batteries, dealers and service shops that handle them are subject to various regulations issued by OSHA, EPA, DOT, and various state or local agencies. Other regulations may also apply in other locations. Always know and follow these regulations when handling batteries.

Batteries that are no longer wanted must be disposed of by an approved battery re-cycler and must never be thrown in the trash or sent to a landfill.

Batteries that are not part of the vehicle itself, not the battery under the hood, must only be transported on public streets for business purposes via approved hazardous material transportation procedures.

Battery storage, charging, and testing facilities in repair shops must meet various requirements for ventilation, safety equipment, material segregation, etc.

The maintenance-free battery is standard. There are no vent plugs in the cover. The battery is completely sealed except for 2 small vent holes in the side. These vent holes allow the small amount of gas that is produced in the battery to escape.

The battery specification label, example below, contains information about the following

1. The test ratings
2. The original equipment catalog number
3. The recommended replacement model number

Scheme 17

Battery Ratings

A battery may have 3 ratings

1. Amp hour (AH)
2. Reserve capacity (RC)
3. Cold cranking amperage (CCA)

When a battery is replaced, use a battery with similar ratings. Refer to the battery specification label on the original battery or refer to Battery Usage .

Amp Hour (AH)

The amp hour rating of a battery is the amount of time it takes a fully charged battery, being discharged at a constant rate of 1 amperes and a constant temperature of 27°C (80°F), to reach a terminal voltage of 10.5 volts. Refer to Battery Usage for the amp hour rating of the original equipment battery.

Cold Cranking Amperage (CCA)

The cold cranking amperage is an indication of the ability of the battery to crank the engine at cold temperatures. The cold cranking amperage rating is the minimum amperage the battery must maintain for 30 seconds at -18°C (0°F) while maintaining at least 7.2 volts. Refer to Battery Usage for the cold cranking amperage rating for this vehicle.

The following information is for the 12-Volt battery only.

For information about charging the high voltage drive motor batteries, refer to Jump Assist Description and Operation .

Drive Motor/Generators

The drive motor/generators are serviceable components located within the transmission housing. When the rotors are spun, an alternating current (AC) is induced into the stator windings. This AC voltage is then sent to the drive motor generator power inverter module (PIM) where it is converted to high voltage direct current (DC) power. The output of the PIM is converted into low voltage electrical power by the accessory DC power converter module (APM) for use by the vehicle's electrical system to maintain electrical loads and battery charge.

Body Control Module (BCM)

The body control module (BCM) is a GMLAN device. It communicates with the engine control module (ECM) and the instrument panel cluster (IPC) for electrical power management (EPM) operation. The BCM determines the desired voltage set point and sends the information to the APM. The BCM monitors a battery current sensor, the battery positive voltage circuit, and estimated battery temperature to determine battery state of charge (SOC).

Battery Current Sensor

The battery current sensor is a serviceable component that is connected to the negative battery cable at the battery. The battery current sensor is a 3-wire hall effect current sensor. The battery current sensor monitors the battery current. It directly inputs to the BCM. It 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 5-95 percent. Between 0-5 percent and 95-100 percent are for diagnostic purposes.

Engine Control Module (ECM)

The ECM receives control decisions based on messages from the BCM.

Instrument Panel Cluster (IPC)

The IPC provides a means of customer notification in case of a failure and a voltmeter. There are 2 means of notification, a charge indicator and a driver information center (DIC) message of SERVICE BATTERY CHARGING SYSTEM.

Battery Sulfation Mode

The BCM will enter this mode when the interpreted charging system voltage is less than 13.2 volts for 30 minutes. When this condition exists the BCM will enter Normal Mode for 5 minutes. The BCM will then determine which mode to enter depending on voltage requirements.

Normal Mode

The BCM will enter Normal Mode when ever one of the following conditions are met.

1. The wipers are ON for more than 3 seconds.
2. GMLAN Climate Control Voltage Boost Mode Request is true, as sensed by the HVAC control head. High speed cooling fan, rear defogger and HVAC high speed blower operation can cause the BCM to enter the Charge Mode.
3. The estimated battery temperature is less than 0°C (32°F).
4. Vehicle Speed is greater than 145 km/h (90 mph)
5. Current Sensor Fault Exists
6. System Voltage was determined to be below 12.56 volts
7. Tow/Haul Mode is enabled

When any one of these conditions is met, the system will set targeted generator output voltage to a charging voltage between 13.9-15.5 volts, depending on the battery state of charge and estimated battery temperature.

Fuel Economy Mode

The BCM will enter Fuel Economy Mode when the ambient air temperature is at least 0°C (32°F) but less than or equal to 80°C (176°F), the calculated battery current is greater than -8 amps but less than 5 amps, and the battery state of charge (SOC) is greater than or equal to 85 percent. Its targeted APM set-point voltage is the open circuit voltage of the battery and can be between 12.6-13.2 volts. The BCM will exit this mode and enter Normal Mode when any of the conditions described above are present.

Headlamp Mode

The BCM will enter Headlamp Mode when ever the high or low beam headlamps are ON. Voltage will be regulated between 13.9-14.5 volts

Voltage Reduction Mode

The BCM will enter Voltage Reduction Mode when the calculated battery temperature is above 0°C (32°F) and the calculated battery current is greater than -7 amps but less than 1 amp. Its targeted APM set-point voltage is 12.9-13.2 volts. The BCM will exit this mode once the criteria are met for Normal Mode.

SERVICE BATTERY CHARGING SYSTEM

The BCM and the ECM will send a GMLAN message to the DIC for the SERVICE BATTERY CHARGING SYSTEM message to be displayed. It is displayed whenever the charge indicator is commanded ON due to a failure.