Engine Electrical (battery) - Hybrid (hp2) GMC Sierra 2500

Fastener Tightening Specifications

Fastener Tightening Specifications

Battery Usage

Light Duty and Auxiliary Batteries

Heavy Duty, Snow Plow, and Dual Generators

Scheme 19

Diagnostic Code Index

DIAGNOSTIC CODE INDEX

Diagnostic Instructions

1. Perform the «Diagnostic System Check - Vehicle»(/gmc/sierra-2500/2012-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/gmc/sierra-2500/2012-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/gmc/sierra-2500/2012-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Circuit/System Description

The vehicle control modules or sensors monitor the system voltage to verify the system voltage is within the normal operating range.

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC

The control module or sensor detects a system voltage of less than approximately 9 V for approximately 5 seconds.

Action Taken When the DTC Sets

1. A driver information center message and/or warning indicator may be displayed.
2. The control module may be temporarily disabled.

Conditions for Clearing the DTC

The system voltage returns to normal operating range.

Diagnostic Aids

1. A high or low voltage DTC set or voltage value in multiple modules/sensors indicates a concern in the charging system.
2. A possible cause of this DTC could be overcharging with a battery charger or jump starting.

Reference Information

Schematic Reference

Control Module References

Connector End View Reference

WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

Charging System Description and Operation

Electrical Information Reference

1. «Circuit Testing»(/gmc/sierra-2500/2012-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/gmc/sierra-2500/2012-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/gmc/sierra-2500/2012-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/gmc/sierra-2500/2012-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

1. Ignition OFF, measure and record the battery voltage at the battery terminals. The battery voltage should stabilize between 12.4 and 12.8 V within a few minutes of turning the ignition OFF. If not within the specified range, refer to «Battery Inspection/Test»(/gmc/sierra-2500/2012-2012/remont/charging-system/#battery-charging-system-and-starting-system) .
2. Engine running, accessories OFF, measure and record the battery voltage at the battery terminals. The voltage should be at least 1 V greater than the voltage measured in step 1 but less than 15 V. If not within the specified range, refer to «Charging System Test»(/gmc/sierra-2500/2012-2012/remont/charging-system/#battery-charging-system-and-starting-system) .
3. Observe the appropriate module scan tool B+ and ignition voltage parameters. The voltage readings should be within 1 V of the battery voltage.

Circuit/System Testing

Note. Use the schematic to identify the following: Control modules the vehicle is equipped with The control modules ground, B+, and Ignition circuit terminal IDs and connectors

1. Ignition OFF, disconnect the harness connectors at the appropriate control module.
2. Ignition OFF, scan tool disconnected, open and close the driver door and wait 1 minute. Test for less than 10 ohms between each ground circuit terminal and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
3. If equipped, verify that a test lamp illuminates between each B+ circuit terminal and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
4. If equipped, ignition ON, verify that a test lamp illuminates between each ignition circuit terminal and ground. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
5. If all circuits test normal, replace the control module module.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for control module replacement, setup, and programming

1. Perform the «Diagnostic System Check - Vehicle»(/gmc/sierra-2500/2012-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/gmc/sierra-2500/2012-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/gmc/sierra-2500/2012-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Diagnostic Fault Information

Typical Scan Tool Data

Battery Current - BCM

Battery Voltage - BCM

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.

B1516 08

The BCM is awake.

B1516 66

1. The BCM is awake.
2. The engine is OFF.
3. The hood and doors are closed.
4. DTC B1516 08 has run and passed during this ignition cycle.
5. DTC B1516 66 has not already run and passed during this ignition cycle.

B1516 08

The BCM detects the PWM duty cycle on the sensor signal circuit is less than 4 percent or greater than 96 percent for 2 minutes.

B1516 66

The BCM detects positive battery current when the engine is OFF.

Regulated voltage control (RVC) is disabled.

1. The DTC passes when the 12V battery sensed current returns to normal range for 15 seconds.
2. A history DTC will clear after 100 ignition cycles.

Schematic Reference

1. «Starting and Charging Schematics»(/gmc/sierra-2500/2012-2012/remont/charging-system/#engine-electrical-battery-hybrid-hp2)
2. «Body Control System Schematics»(/gmc/sierra-2500/2012-2012/remont/communication-devices/#data-communications-system)

Connector End View Reference

WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

Charging System Description and Operation

Electrical Information Reference

1. «Circuit Testing»(/gmc/sierra-2500/2012-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/gmc/sierra-2500/2012-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/gmc/sierra-2500/2012-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/gmc/sierra-2500/2012-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

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.

1. Ignition ON, observe the scan tool BCM Battery Voltage parameter. The reading should be equal to B+ voltage. If not the specified value, test the following BCM circuits for an open/high resistance. If the circuits test normal, replace the BCM. B+ circuit terminal 3 X3 Ground circuit terminal 1 X3 Ground circuit terminal 5 X3 Ground circuit terminal 9 X4
2. Verify that the current sensor is mounted correctly on the 12V battery cable. The sensor should be installed with the internal coil around the negative battery cables, with the tape tab pointing away from the battery. If the sensor is not installed correctly, remove and reinstall the sensor.
3. Ignition OFF, disconnect the harness connector at the battery current sensor.
4. Ignition OFF and scan tool disconnected, open and close the driver door, and wait 1 minute. Test for less than 5 ohms between the low reference circuit terminal B and ground. If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the BCM.
5. Ignition ON, test for 4.5-5.5 volts between the 5-volt reference circuit terminal A and ground. If not within the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
6. Ignition ON, test for 4.5-5.5 volts between the signal circuit terminal C and ground. If not within the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
7. If all circuits test normal, replace the battery current sensor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Battery Current Sensor Replacement»(/gmc/sierra-2500/2012-2012/remont/charging-system/#engine-electrical-battery-hybrid-hp2)
2. «Control Module References»(/gmc/sierra-2500/2012-2012/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for BCM replacement, setup, and programming

1. Perform the «Diagnostic System Check - Vehicle»(/gmc/sierra-2500/2012-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/gmc/sierra-2500/2012-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/gmc/sierra-2500/2012-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The body control module (BCM) monitors the state of charge (SOC) of the 12V electrical system. If the BCM senses that the 12V 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 ignition is turned from Off to Accessory or Run.

1. The SOC at key-on is 30 percent lower than when the engine was last running.
2. The 12V battery drain is greater than 2 amps.

No actions are taken. This DTC sets as an aid to the technician.

1. The DTC will clear when the SOC is greater than or equal to 80 percent.
2. A history DTC clears after 50 consecutive ignition cycles that the diagnostic runs and does not fail.

Schematic Reference

Starting and Charging Schematics

Connector End View Reference

WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

Charging System Description and Operation

Electrical Information Reference

1. «Circuit Testing»(/gmc/sierra-2500/2012-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/gmc/sierra-2500/2012-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/gmc/sierra-2500/2012-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/gmc/sierra-2500/2012-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

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»(/gmc/sierra-2500/2012-2012/remont/charging-system/#engine-electrical-battery-hybrid-hp2) .

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. Perform the «Diagnostic System Check - Vehicle»(/gmc/sierra-2500/2012-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/gmc/sierra-2500/2012-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/gmc/sierra-2500/2012-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

HPCM 300V Circuit - APM

High Battery Voltage - ACCM

The air conditioner control module (ACCM) monitors the high voltage direct current (HVDC) 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. If the ACCM detects low HVDC voltage, then DTC P0AFA will set.

1. The engine is running or is in autostop mode.
2. The 12V system voltage is between 9.5-18 V.

The ACCM detects that the hybrid battery voltage is less than 191 volts for 3 seconds.

The air conditioning is disabled.

1. The DTC will pass when the ACCM detects a hybrid battery voltage greater than 201 V for 3 seconds.
2. A history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.

Schematic Reference

1. «HVAC Schematics»(/gmc/sierra-2500/2012-2012/remont/automatic-hvac-system/#hvac-system-automatic)
2. «Hybrid Controls Schematics»(/gmc/sierra-2500/2012-2012/remont/body-electrical/#hybridev-control-system)

Connector End View Reference

WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

1. «Heating and Air Conditioning System Description and Operation (HP2)»(/gmc/sierra-2500/2012-2012/remont/automatic-hvac-system/#heating-ventilation-and-air-conditioning)
2. «High Voltage Monitoring Systems Description»(/gmc/sierra-2500/2012-2012/remont/body-electrical/#hybridev-control-system__high-voltage-monitoring-systems-description)

Electrical Information Reference

1. «Circuit Testing»(/gmc/sierra-2500/2012-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/gmc/sierra-2500/2012-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/gmc/sierra-2500/2012-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/gmc/sierra-2500/2012-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Special Tools

EL-48900 HEV Safety Kit

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»(/gmc/sierra-2500/2012-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-trouble-code-dtc-list) .
2. Engine running or autostop, observe the scan tool accessory DC power control module (APM) HPCM 300V Circuit parameter. The reading should be between 225 V and 380 V. If not within the specified range, refer to «Jump Assist»(/gmc/sierra-2500/2012-2012/remont/body-electrical/#hybridev-energy-storage-system) .
3. Ignition ON, observe the scan tool ACCM High Battery Voltage parameter. The reading should be between 225 V and 380 V.

1. Disable the high voltage, and remove the 3 phase cable cover. Refer to «High Voltage Disabling»(/gmc/sierra-2500/2012-2012/remont/body-electrical/#hybridev-energy-storage-system__high-voltage-disabling) .
2. Ignition OFF, verify that the air conditioner compressor HVDC terminal bolts are present and are torqued to specification. If the bolts are missing or are not tight, replace any damaged components, install and tighten the bolts.
3. If all circuits test normal, replace the ACCM.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for ACCM replacement, setup, and programming

1. Perform the «Diagnostic System Check - Vehicle»(/gmc/sierra-2500/2012-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/gmc/sierra-2500/2012-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/gmc/sierra-2500/2012-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

HPCM 300V Circuit - APM

High Battery Voltage - ACCM

The air conditioner control module (ACCM) monitors the high voltage direct current (HVDC) 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. If the ACCM detects high HVDC voltage, then DTC P0AFB will set.

1. The engine is running or is in autostop mode.
2. The 12 V system voltage is between 9.5-18 V.

The ACCM detects that the hybrid battery voltage is greater than 415 V for 3 seconds.

The air conditioning is disabled.

1. The DTC will pass when the ACCM detects a hybrid battery voltage less than 405 V for 3 seconds.
2. A history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.

A high voltage DTC in multiple modules indicates a concern in the charging system.

Schematic Reference

1. «HVAC Schematics»(/gmc/sierra-2500/2012-2012/remont/automatic-hvac-system/#hvac-system-automatic)
2. «Hybrid Controls Schematics»(/gmc/sierra-2500/2012-2012/remont/body-electrical/#hybridev-control-system)

Connector End View Reference

WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

1. «Heating and Air Conditioning System Description and Operation (HP2)»(/gmc/sierra-2500/2012-2012/remont/automatic-hvac-system/#heating-ventilation-and-air-conditioning)
2. «High Voltage Monitoring Systems Description»(/gmc/sierra-2500/2012-2012/remont/body-electrical/#hybridev-control-system__high-voltage-monitoring-systems-description)

Electrical Information Reference

1. «Circuit Testing»(/gmc/sierra-2500/2012-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/gmc/sierra-2500/2012-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/gmc/sierra-2500/2012-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/gmc/sierra-2500/2012-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

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»(/gmc/sierra-2500/2012-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-trouble-code-dtc-list) .
2. Engine running or autostop, observe the scan tool ACCM High Battery Voltage parameter. The reading should be between 225 V and 380 V. 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»(/gmc/sierra-2500/2012-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) 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»(/gmc/sierra-2500/2012-2012/remont/charging-system/#engine-electrical-battery-hybrid-hp2) «Charging System Description and Operation»(/gmc/sierra-2500/2012-2012/remont/charging-system/#engine-electrical-battery-hybrid-hp2) «Starting System Description and Operation»(/gmc/sierra-2500/2012-2012/remont/charging-system/#engine-electrical-battery-hybrid-hp2__starting-system-description-and-operation)

Visual/Physical Inspection

1. Inspect the high voltage system. Refer to «High Voltage System Inspection»(/gmc/sierra-2500/2012-2012/remont/body-electrical/#hybridev-control-system) .
2. Inspect for aftermarket devices which could affect the operation of the 12 V charging system. Refer to «Checking Aftermarket Accessories»(/gmc/sierra-2500/2012-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__checking-aftermarket-accessories) .
3. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.

Intermittent

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

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom

1. «Battery Inspection/Test»(/gmc/sierra-2500/2012-2012/remont/charging-system/#engine-electrical-battery-hybrid-hp2)
2. «Battery Charging»(/gmc/sierra-2500/2012-2012/remont/charging-system/#engine-electrical-battery-hybrid-hp2)
3. «Battery Electrical Drain/Parasitic Load Test»(/gmc/sierra-2500/2012-2012/remont/charging-system/#engine-electrical-battery-hybrid-hp2)
4. «Charging System Test»(/gmc/sierra-2500/2012-2012/remont/charging-system/#engine-electrical-battery-hybrid-hp2__charging-system-test)

1. Perform the «Diagnostic System Check - Vehicle»(/gmc/sierra-2500/2012-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/gmc/sierra-2500/2012-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/gmc/sierra-2500/2012-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Note. The battery test using the regionally available battery tester requires correct connections to the battery terminals. Ensure that battery tester clamps are connected directly to either the battery post or the battery cable terminal. Do not connect clamps to battery cable fasteners. Failure to obtain the correct connections during the test may result in a failed test on a good battery. Use the Out of Vehicle test for each battery when testing a vehicle with dual batteries.

Follow these instructions in order to avoid an incorrect diagnosis because of connections

1. If testing the vehicle with the battery cables still connected, wiggle the battery tester clips on the terminal. This may cut through any coating or through any oxidation that may be present on the terminal.
2. If correct connections to the battery terminals in the vehicle are in doubt, perform the following steps: Disconnect the negative battery cable. Disconnect the positive battery cable. Follow the instructions for testing a removed battery.
3. If the tester displays a REPLACE BATTERY or BAD CELL-REPLACE result for a battery tested in the vehicle with the battery cables connected, perform the following steps: Disconnect the negative battery cable. Disconnect the positive battery cable. NOTE: Always write the test code displayed by the tester on the repair order for any warranty purposes. The number is a unique code that describes the test data for a particular battery at a particular time. The test code may occasionally repeat when you retest the same battery. More often, each test will result in a different code. Use the test code from the second, or Out of Vehicle test. Follow the instructions for testing a removed battery. Replace the battery only if the second test shows a REPLACE BATTERY or BAD CELL-REPLACE result. Use the test code from the second test for any warranty purposes.

Schematic Reference

Starting and Charging Schematics

Connector End View Reference

WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

Starting System Description and Operation

Electrical Information Reference

1. «Circuit Testing»(/gmc/sierra-2500/2012-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/gmc/sierra-2500/2012-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/gmc/sierra-2500/2012-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/gmc/sierra-2500/2012-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Special Tools

Battery Tester, for regionally available devices, refer to Special Tools .

1. Verify the C1 battery case is not cracked, broken, or damaged, which may be indicated by battery acid leakage. If there is any apparent damage Replace the C1 battery. If there is no damage
2. Verify the cold cranking amperage and amperage hour rating of the C1 battery. Refer to the manufacturer specifications on the battery label. If the C1 battery does not meet or exceed specifications Replace the C1 Battery. If the C1 Battery meets or exceeds specifications
3. Verify that the battery cables are clean and tight. The battery terminal bolts should be torqued as specified in «Fastener Tightening Specifications»(/gmc/sierra-2500/2012-2012/remont/charging-system/#battery-charging-system-and-starting-system__fastener-tightening-specifications) . If the battery cables need to be cleaned or tightened Clean as required and tighten as specified. If the battery cables are clean and tight
4. Install the battery tester and follow directions supplied by the tester.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Battery Replacement

12 V Battery

The following procedure is for the 12 V battery only.

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

Special Tools

EL 42000 Battery Tester

For equivalent regional tools, refer to Special Tools .

1. For best results, use an automatic taper-rate battery charger with a voltage capability of 16 volts.
2. The charging area should be well ventilated.
3. Do not charge a battery that appears to be frozen. Allow the battery to warm to room temperature and test it using the EL 42000 before charging.

Battery State of Charge

Note. Using voltage to determine the 12 V batteries state of charge 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 state of charge will only be an estimate.

The maintenance-free batteries state of charge 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 state of charge

1. Be sure all electrical loads are turned OFF.
2. Determine whether the 12 V 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 state of charge according to the estimated battery temperature

Battery Charging

Use the state of charge information as follows

1. A battery with a state of charge that is below 65 percent must always be recharged before returning it to service or continuing storage.
2. A battery with a state of charge 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 12 V 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 12 V 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 state of charge of the 12 V 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 V, 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 12 V 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 12 V battery. Refer to «Battery Inspection/Test»(/gmc/sierra-2500/2012-2012/remont/charging-system/#battery-charging-system-and-starting-system) .

1. Perform the «Diagnostic System Check - Vehicle»(/gmc/sierra-2500/2012-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/gmc/sierra-2500/2012-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/gmc/sierra-2500/2012-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

12 V Battery

The following procedure is for the 12 V battery only.

Components most likely to cause a parasitic draw on the vehicle's battery are switches, relays, and control modules. After the ignition is turned OFF the control modules will begin to go to sleep (shut OFF). All control modules do not go to sleep at the same time, some may take up to 30 minutes or longer after turning the ignition off before going to sleep, like the HVAC and body control modules. Others such as the ON Star and keyless entry control modules may periodically wake up then go back to sleep. These are all normal conditions.

1. Rule out any possible aftermarket equipment causing an unacceptable parasitic current drain. Aftermarket accessories installed into the courtesy lamp circuit can cause the inadvertent power timer in the body control module (BCM) to keep resetting. This would cause the BCM to remain awake and cause a current drain on the battery.
2. Rule out customer driving habits such as regular short trips that do not allow enough time to properly charge the battery. Refer to «Battery Description and Operation»(/gmc/sierra-2500/2012-2012/remont/charging-system/#engine-electrical-battery-hybrid-hp2) .
3. Verify that the battery and charging system are in proper working order. Refer to «Battery Charging»(/gmc/sierra-2500/2012-2012/remont/charging-system/#engine-electrical-battery-hybrid-hp2) , and «Charging System Test»(/gmc/sierra-2500/2012-2012/remont/charging-system/#engine-electrical-battery-hybrid-hp2__charging-system-test) .
4. A battery discharging for no apparent reason while the vehicle is parked can be caused by an intermittent draw, such as a module waking up, or a continuous draw, such as a dome light or stuck relay.
5. Some systems and modules such as OnStar®, and regulated voltage control (RVC), if equipped, are designed to wake-up, perform a task, and go back asleep at regular intervals. Refer to «Body Control System Description and Operation»(/gmc/sierra-2500/2012-2012/remont/communication-devices/#data-communications-system__body-control-system-description-and-operation) for the system or modules description and operation.
6. An engine off natural vacuum evaporative test can occur if the engine control module (ECM) determines the drive cycle has met the appropriate criteria immediately after key off. The ECM will stay awake and the vent solenoid will stay energized for as long as 45 minutes. The typical current draw for this is about 1 A.
7. Digital OnStar gen 6 and later VCIMs do not "wake up" every 10 minutes for the first 48 hours as the gen 5 and prior. Gen 6 and later VCIM current draw is very low, less than 40 mA, so the OnStar system is left in that state for up to the first 48 hours. Parasitic draw of up to 40 mA with an occasional spike as high as 80 mA through the VCIM for the first 48 hours is normal.
8. Some automatic climate control systems can remain in a semi-awake state for up to three hours, actual draw amounts vary by vehicle platform but are typically not greater than 50 mA.
9. An extremely low mA current level is consumed by the RKE receiver for monitoring purposes, actual system wake up only occurs when the fobs for the vehicle are used. When other devices on the same RKE operating frequency are activated, such as the 4 tire pressure monitoring sensors and other vehicle FOB's in the vicinity, the RKE receiver will have a 100 mA spike. These spikes are normal and occur too briefly to have a significant effect on battery drain. Competing signals may cause RKE performance issues such as jamming but should not cause excessive battery draw.
10. If an excessive current draw is not present during initial testing, continue periodic testing over a 1-2 hour period to see if the current draw increases and stays above an unacceptable level.
11. The battery run down time will vary depending on the batteries reserve capacity. If the reserve capacity is higher, then the battery run down time would be longer. If the reserve capacity is lower, then the battery run down time would be shorter. The graph below indicates roughly how many days a 690 cold cranking amp battery with a 110 min. reserve capacity starting at 80 percent state of charge will last with a constant current draw until it reaches 50 percent state of charge. Differences in battery reserve capacity and temperature will affect the results.

Schematic Reference

Control Module References

Connector End View Reference

WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS - INDEX

Electrical Information Reference

1. «Circuit Testing»(/gmc/sierra-2500/2012-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Testing for Intermittent Conditions and Poor Connections»(/gmc/sierra-2500/2012-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
3. «Connector Repairs»(/gmc/sierra-2500/2012-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
4. «Wiring Repairs»(/gmc/sierra-2500/2012-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Special Tools

EL 38758 Parasitic Draw Test Switch

For equivalent regional tools, refer to Special Tools .

Note. Most vehicle systems will go to sleep within 30 minutes but it can take up to 2 hours before all systems power down allowing the parasitic draw test to pass. An occasional increase in the parasitic draw is normal as long as it returns within 1 second. Closing the door latches/ajar switch while leaving the doors open is recommended, this allows the vehicle systems to perform in a "doors closed" mode while allowing vehicle interior access that may be needed to complete the diagnostic steps. Locking doors will arm the vehicle content theft deterrent system if equipped. Failure to arm the system may cause a theft system fault to not be present during testing. There are many things that can prevent the vehicle from completely going to sleep and passing the parasitic draw test. Make sure all the conditions listed below are met before performing the parasitic current draw test. Ignition OFF Key out of the ignition switch - when not equipped with keyless access and start Retained Accessory Power RAP OFF - open and close the driver door after ignition OFF Scan tool not communicating with a vehicle control module - in some cases it may need to be disconnected from the DLC All access doors closed Headlamps OFF - auto headlamps disabled Any delay lighting OFF If equipped with an under hood lamp disable it HVAC after blow OFF Any accessory that can work with ignition OFF inactive or OFF Wait up to 2 minutes or longer, after all other listed conditions are met

Using an Inductive Pickup Probe

1. Connect an inductive pickup probe to the negative battery cable that can read down to 1 mA.
2. Ignition OFF, as the vehicle systems shut down test for less than 30 mA of parasitic current drain. If greater than the specified range, refer to Circuit/System Testing below.

Using the EL 38758 Parasitic Draw Test Switch

1. Ignition OFF, disconnect the battery negative cable from the battery. Refer to «Battery Negative Cable Disconnection and Connection (TP2)»(/gmc/sierra-2500/2012-2012/remont/charging-system/#battery-charging-system-and-starting-system) , «Battery Negative Cable Disconnection and Connection (Single Battery)»(/gmc/sierra-2500/2012-2012/remont/charging-system/#battery-charging-system-and-starting-system) .
2. Turn the EL 38758 switch knob to the OFF position.
3. Install the male end of the EL 38758 switch to the battery ground terminal.
4. Install the battery negative cable to the female end of the EL 38758 switch.
5. Turn the EL 38758 switch knob to the ON position.
6. Road test the vehicle and activate all of the accessories such as the radio and air conditioning.
7. Ignition OFF, connect a 10 A fused jumper wire to the test switch tool terminals.
8. Turn the EL 38758 switch knob to the OFF position. The current now flows through the jumper wire.
9. Check the fuse in the jumper wire. The fuse should be OK. If the jumper wire fuse is blown, refer to Circuit/System Testing below.
10. Turn the EL 38758 switch knob to the ON position. Remove the fused jumper wire.
11. Connect a DMM set to the 10 A DC scale between the test switch tool terminals.
12. Turn the EL 38758 switch knob to the OFF position. The current now flows through the DMM.
13. As the vehicle systems shut down test for less than 30 mA of parasitic current drain. If greater than the specified range, refer to Circuit/System Testing below.

Note. Removing or installing a fuse, relay, or connector, to determine the area causing high parasitic draw may wake up control modules. You must wait for the control modules to go back to sleep before retesting. It is best to install any removed or disconnected components after the diagnosis is completed. Fuses for power mode master components such as the BCM should be removed last to avoid misdiagnosis. If a scan tool is connected to the DLC, either disconnect it or subtract the scan tool current draw from the DMM reading to get the actual vehicle parasitic current draw.

If the vehicle has an unacceptable amount of parasitic current draw, remove each fuse one at a time until the current draw falls to an acceptable level. A drop of more than 10-20 mA, when disabling a single system or circuit, is an indication of an overly high current draw that could be causing the battery drain. Refer to Power Distribution Schematics to diagnose exactly which circuit of the suspect system is causing the high parasitic drain. The follow is a list of common components that could cause a high current draw

1. Stuck switch
2. Stuck relay
3. Control module

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for control module replacement, setup and programming

Charging System Test

The accessory power module (APM) supplies the energy that flows between the high voltage (300 volt) direct current (DC) and low voltage (14 volt) DC to charge the 12 volt battery and power accessories. To test the charging system, refer to DC Power Conversion Test .

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.

Removal Procedure

1. Remove the negative battery cable. Refer to «Battery Negative Cable Replacement»(/gmc/sierra-2500/2012-2012/remont/charging-system/#engine-electrical-battery-hybrid-hp2) .
2. Mark the location of the negative battery cable clip (1) and remove the clip from the cable.
3. Mark the location of the battery current sensor (2) on the battery cable with tape for reference during installation.
4. Remove the tape securing the battery current sensor to the negative battery cable.
5. Squeeze the negative battery cable branches together.
6. Slide the battery current sensor (2) off of the negative battery cable.

Installation Procedure

1. Squeeze the negative battery cable branches together.
2. Slide the NEW battery current sensor (2) up onto the negative battery cable to the location previously marked during removal.
3. Wrap electrical tape around the battery current sensor leg in order to secure the sensor to the negative battery cable.
4. Install the negative battery cable clip (1) to the cable to the location previously marked during removal.
5. Install the negative battery cable. Refer to «Battery Negative Cable Replacement»(/gmc/sierra-2500/2012-2012/remont/charging-system/#engine-electrical-battery-hybrid-hp2) .

1. Disconnect the negative battery cable. Refer to «Battery Negative Cable Disconnection and Connection»(/gmc/sierra-2500/2012-2012/remont/charging-system/#engine-electrical-battery-hybrid-hp2) .
2. Disconnect the engine wiring harness electrical connector (1) from the battery current sensor (2).
3. Remove the negative battery cable clip (1) from the auxiliary bussed electrical center (BEC).
4. Remove the negative battery cable ground terminal bolt (1) from the left side engine block boss.
5. Remove the negative battery cable (3) and the engine wiring harness ground (2) leads from the engine block boss.
6. Raise and suitably support the vehicle. Refer to «Lifting and Jacking the Vehicle»(/gmc/sierra-2500/2012-2012/remont/ignition-switchsteering-lock/#general-information__lifting-and-jacking-the-vehicle) .
7. Remove the engine wiring harness ground lead bolt (1) from the frame.
8. Remove the engine wiring harness ground lead (2) and the negative battery cable lead (3) from the frame.
9. Lower the vehicle.
10. Remove the negative battery cable assembly (1) from under the positive battery cable and from the vehicle.

1. Install the negative battery cable assembly (1) to the vehicle and route the cable under the positive battery cable.
2. Raise and suitably support the vehicle.
3. Position the negative battery cable lead (3) behind the engine wiring harness ground lead (2).
4. Place the engine wiring harness ground lead (2) and the negative battery cable lead (3) to the frame.
5. Insert the anti-rotation tab on the engine harness ground lead into the hole in the frame.
6. Install the engine wiring harness ground lead to the frame bolt (1) and tighten to 9 N.m (80 lb in).
7. Lower the vehicle.
8. Position the engine wiring harness ground lead (2) behind the negative battery cable lead (3).
9. Place the negative battery cable lead (3) and the engine wiring harness ground lead (2) against the engine block boss.
10. Install the negative battery cable ground terminal to the engine block boss bolt (1) and tighten to 50 N.m (37 lb ft).
11. Install the negative battery cable clip (1) to the auxiliary BEC.
12. Connect the engine wiring harness electrical connector (1) to the battery current sensor (2).
13. Connect the negative battery cable. Refer to «Battery Negative Cable Disconnection and Connection»(/gmc/sierra-2500/2012-2012/remont/charging-system/#engine-electrical-battery-hybrid-hp2) .

1. Disconnect the negative battery cable. Refer to «Battery Negative Cable Disconnection and Connection»(/gmc/sierra-2500/2012-2012/remont/charging-system/#engine-electrical-battery-hybrid-hp2) .
2. Reposition the positive battery cable insulating cover (2) from over the positive terminal.
3. Rotate the lever lock (1) counterclockwise in order to disconnect the positive battery cable.
4. Remove the positive battery cable terminal (3) from the battery.
5. Remove the auxiliary bussed electrical center (BEC) cover (1).
6. Remove the underhood junction block cover.
7. Lift the junction block retainers from the locked position (3) and rotate the retainers to the open position (1).
8. Remove the junction block.
9. Remove the positive battery cable nut (1) from the mega fuse stud.
10. Remove the positive battery cable nut (3) from the auxiliary BEC stud.
11. Disconnect the positive battery cable connector (2) from the underhood BEC.
12. Remove the positive battery cable assembly (1) from the vehicle.

1. Install the positive battery cable assembly (1) to the vehicle.
2. Install the positive battery cable leads to the mega fuse and auxiliary BEC studs.
3. Connect the positive battery cable connector (2) to the underhood BEC.
4. Install the positive battery cable nut (3) to the auxiliary BEC stud and tighten to 9 N.m (80 lb in).
5. Install the positive battery cable nut (1) to the mega fuse stud and tighten to 9 N.m (80 lb in).
6. Ensure that the junction block retainers are in the open position (1).
7. Position and align the junction block to the 4 bracket pivots (2), once the pivots are engaged, push the retainers down into the locked position (3).
8. Install the underhood junction block cover.
9. Install the auxiliary BEC cover (1).
10. Install the positive battery cable terminal (3) to the battery.
11. Rotate the lever lock (1) clockwise until an audible click is heard in order to connect the positive battery cable.
12. Position the positive battery cable insulating cover (2) over the positive terminal.
13. Connect the negative battery cable. Refer to «Battery Negative Cable Disconnection and Connection»(/gmc/sierra-2500/2012-2012/remont/charging-system/#engine-electrical-battery-hybrid-hp2) .

1. Disconnect the negative battery cable. Refer to «Battery Negative Cable Disconnection and Connection»(/gmc/sierra-2500/2012-2012/remont/charging-system/#engine-electrical-battery-hybrid-hp2) .
2. Reposition the positive battery cable insulating cover (2) from over the positive terminal.
3. Rotate the lever lock (1) counterclockwise in order to disconnect the positive battery cable.
4. Remove the positive battery cable terminal (3) from the battery.
5. Remove the battery hold down bolt (1) and hold down (3).
6. Remove the battery assembly (2).

1. Install the battery assembly (2).
2. Install the battery hold down (3) and bolt (1) and tighten to 25 N.m (18 lb ft).
3. Install the positive battery cable terminal (3) to the battery.
4. Rotate the lever lock (1) clockwise until an audible click is heard in order to connect the positive battery cable.
5. Position the positive battery cable insulating cover (2) over the positive terminal.
6. Connect the negative battery cable. Refer to «Battery Negative Cable Disconnection and Connection»(/gmc/sierra-2500/2012-2012/remont/charging-system/#engine-electrical-battery-hybrid-hp2) .

1. Remove the battery. Refer to «Battery Replacement»(/gmc/sierra-2500/2012-2012/remont/charging-system/#engine-electrical-battery-hybrid-hp2) .
2. Reposition the positive and negative battery cables out of the way.
3. Remove the battery tray to battery tray reinforcement bolts (1).
4. Remove the battery tray to battery tray support bolts (2).
5. Remove the battery tray to auxiliary bussed electrical center (BEC) bolt (4).
6. Remove the battery tray (3).

1. Install the battery tray (3) into the vehicle.
2. Install the battery tray to battery tray reinforcement bolts (1) and tighten to 9 N.m (80 lb in).
3. Install the battery tray support bolts (2) and tighten to 9 N.m (80 lb in).
4. Install the battery tray to auxiliary BEC bolt (4) and tighten to 9 N.m (80 lb in).
5. Install the positive and negative battery cables.
6. Install the battery. Refer to «Battery Replacement»(/gmc/sierra-2500/2012-2012/remont/charging-system/#engine-electrical-battery-hybrid-hp2) .

1. Remove the engine wiring harness ground bolt.
2. Reposition the engine wiring harness ground and ground strap.
3. Remove the ground strap nut from the stud at the front of dash.
4. Remove the ground strap from the stud.

1. Install the ground strap to the stud.
2. Install the ground strap nut to the stud at the front of dash and tighten to 9 N.m (80 lb in).
3. Position the ground strap and engine wiring harness ground.
4. Install the engine wiring harness ground bolt and tighten to 16 N.m (12 lb ft).

Generator Control Module Ground Strap Replacement

1. Remove the air cleaner assembly. Refer to «Upper Intake Manifold Cover Replacement»(/gmc/sierra-2500/2012-2012/remont/mechanical/#engine-mechanical-hybrid-hp2-60l-lz1-repair-instructions-on-vehicle) .
2. Remove the drive motor generator control module ground strap bolt (1) and strap (2).

1. Position the ground strap (2) to the drive motor generator control module.
2. Install the ground strap bolt (1) and tighten to 9 N.m (80 lb in).
3. Install the air cleaner assembly. Refer to «Upper Intake Manifold Cover Replacement»(/gmc/sierra-2500/2012-2012/remont/mechanical/#engine-mechanical-hybrid-hp2-60l-lz1-repair-instructions-on-vehicle) .

300-Volt Battery

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

Scheme 20

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 recycler 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 21

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.

Reserve Capacity (RC)

Reserve capacity is the amount of time in minutes it takes a fully charged battery, being discharged at a constant rate of 25 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 reserve capacity 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.

12-Volt Battery

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 .

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. This EPM system primarily utilizes existing on-board computer capability to maximize the effectiveness of the charging system, 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

1. It monitors the battery voltage and estimates the battery condition.
2. It takes corrective actions by adjusting the regulated voltage.
3. 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.

Charging System Components

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.

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

1. Battery Sulfation Mode
2. Normal Mode
3. Fuel Economy Mode
4. Headlamp Mode
5. Voltage Reduction Mode
6. Plant Assembly Mode

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.

Plant Assembly Mode

The BCM will increase charging voltage for the first 500 miles of operation in an effort to ensure that the 12 volt battery is fully charged when the vehicle is delivered to the customer.

Instrument Panel Cluster (IPC) Operation

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

1. The engine control module (ECM) detects system voltage less than 11 volts or greater than 16 volts. The IPC receives a GMLAN message from the ECM requesting illumination.
2. The BCM determines that the system voltage is less than 11 volts or greater than 16 volts.
3. The IPC receives a GMLAN message from the body control module (BCM) indicating there is a system voltage range concern.
4. The IPC performs the displays test at the start of each ignition cycle. The indicator illuminates for approximately 3 seconds.
5. 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 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.

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.

Starting System Description and Operation

The HP2 hybrid system does not use a conventional starter. Refer to Hybrid Modes of Operation Description for information about the starting system.

Special Tools

Illustration Tool Number/Description EL 38758 EL 50074 J 38758 Parasitic Draw Test Switch EL 50313 EL 42000 EL 50076 J 42000 Battery Tester EL-48900 HEV Safety Kit

Scheme 22

Scheme 23

Scheme 24

See also:
• Diagnostic System Check - Vehicle
• Strategy Based Diagnosis
• Diagnostic Procedure Instructions
• Control Module References
• WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS - INDEX
• Charging System Description and Operation
• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs
• Diagnostic Repair Verification
• Body Control System Schematics
• HVAC Schematics
• Hybrid Controls Schematics
• Heating and Air Conditioning System Description and Operation (HP2)
• High Voltage Monitoring Systems Description
• Diagnostic Trouble Code (DTC) List - Vehicle
• Jump Assist
• High Voltage Disabling
• Checking Aftermarket Accessories
• Battery Disconnect Warning
• Starting System Description and Operation
• Special Tools
• Fastener Tightening Specifications
• Body Control System Description and Operation
• Battery Usage
• Power Distribution Schematics
• Lifting and Jacking the Vehicle
• Fastener Caution
• Upper Intake Manifold Cover Replacement
• Hybrid Modes of Operation Description
• DTC B1325, B1330, B1420, B1424, B1517, C0800, C0895, C0899, C0900, C12E1, C12E2, P0560, P0562, or P0563
• Starting System Description and Operation
• Charging System Test
• Special Tools