Battery Management System

Load Shed Strategy

NOTE: When any vehicle module is being programmed, connect an external battery charger to make sure that the module programming is completed without the interruption due to the load shedding feature becoming active. The external battery charger must maintain a system voltage above 13 volts. This can require a charger setting higher than the lowest charge setting. The external battery charger negative connection must be made to an engine or vehicle chassis ground and not the negative battery terminal. If the connection is to the negative battery terminal, load shedding cannot be prevented from being invoked and module programming may be corrupted. After charging has begun, start the engine to clear any load shed states and then turn the engine off and proceed with programming.

NOTE: To maintain correct operation of the load shed, any electrical devices or equipment must be grounded to the chassis ground and not the negative battery terminal. A connection to the negative battery terminal can cause an inaccurate measurement of the battery state of charge and can cause incorrect load shed system operation.

This vehicle is equipped with a load shed strategy. The Body Control Module (BCM) uses the battery current sensor to keep track of the battery state of charge. The battery current sensor is a Hall-effect sensor attached to the battery ground cable. On vehicles equipped with Intelligent Access (IA), the ignition state can also change.

Engine Off Load Shed

The BCM uses the battery current sensor to keep track of the battery state of charge. The battery current sensor is a Hall-effect sensor attached to the battery ground cable. When the engine is off, and the BCM determines the battery state of charge is below 40%, 10% of the charge has been drained or 45 minutes have elapsed, a load shed message is sent over the Controller Area Network (CAN). This message turns off the audio system to save the remaining battery charge. Under this condition, a message may be displayed on the IPC or center stack display to alert the driver that battery protection actions are active.

When charging the vehicle battery by connecting the charger to the negative battery terminal is necessary , such as when using a combination battery charger and battery tester/analyzer, like the GR 1 190 V3.0 Intelligent Diagnostic Charger, the BCM will not immediately update the battery state of charge. In this instance, after charging, you must CARRY OUT the Battery Monitoring System (BMS) Reset using the scan tool. This reset is needed for proper engine off load shedding and to prevent invoking of engine off load shedding earlier than normal.

NOTE: If the reset is not carried out, when the battery is charged by connecting the charger to the negative battery terminal, it takes approximately 8 hours for the BCM to learn the new battery state of charge. During this 8 hour period, the vehicle must be undisturbed, with no doors opened or keyless entry button presses. If the vehicle is used before the BCM is allowed to learn the new battery state of charge, engine off load shedding can still occur and a message may be displayed.

When charging the vehicle battery by connecting the charger to engine or chassis ground , the negative charger clamp must be connected to an unpainted chassis surface or a solid engine component such as a generator mount or engine lifting eye. In this instance, after charging, the BMS reset is not required if the ignition was ON during charging by above method. Through this method of charging, the BCM updates the battery state of charge during the charging process. If the ignition was OFF during charging by above method, a BMS reset may be required since the BCM does not update battery state of charge with ignition key OFF unless the vehicle is parked undisturbed for 8 hours.

Vehicles without Intelligent Access (IA)

Load shed only occurs when the engine is not running, and the ignition is in the ACC, RUN or delayed accessory position. To clear the load shed state, restart the engine. If load shed occurs, the audio system turns off.

If a fault occurs with the battery current sensor or circuit(s), the only load shed strategy is a 45 minute timer. After 45 minutes have elapsed, the audio system turns off. To clear the load shed state, restart the engine.

Vehicles with Intelligent Access (IA)

Load shed only occurs when the engine is not running, and the ignition is in the ACC, RUN or delayed accessory mode. To clear the load shed state, restart the engine. If the ignition is in RUN and load shed occurs, the audio system turns off and the ignition remains in RUN. If the ignition is in ACC and load shed occurs, the audio system mutes for 1 minute then the ignition mode changes to OFF. For example, if equipped, the memory seats move to the easy exit position and the dome light may illuminate.

If a fault occurs with the battery current sensor or circuits, the only load shed strategy is a 45 minute timer. After 45 minutes have elapsed, the audio system turns off. To clear the load shed state, restart the engine.

Generator Current Sensor

The generator current sensor is attached to the generator B+ cable. The PCM supplies a 5-volt reference and ground to the generator current sensor. The generator current sensor is a Hall-effect sensor that supplies an analog feedback signal to the PCM.

Battery Current Sensor

The battery current sensor is attached to the negative battery cable. The BCM supplies a 5-volt reference and ground to the battery current sensor. The battery current sensor is a Hall-effect sensor that supplies a Pulse-Width Modulation (PWM) feedback signal to the BCM.

Battery Charging

Refer to Battery, Mounting and Cables .