Circuit/System Description
The control modules on this vehicle monitor the battery voltage on the 12V battery positive (B+) voltage circuits. This vehicle has multiple modules that will set the DTC. For information about which modules, refer to Diagnostic Trouble Code (DTC) List - Vehicle .
The theft deterrent module (TDM) monitors the 12V battery positive (B+) voltage available to it. If the voltage at the TDM is between 6-9 volts, and the voltage being reported by a serial data message is greater than 9 volts, then DTC B1424 00 sets.
The battery current sensor is a 3 wire hall effect current sensor. The battery current sensor monitors the battery current. The signal circuit is an input to the body control module (BCM). The sensor creates a 5 volt pulse width modulation (PWM) signal of 128 Hz with a duty cycle of 0-100 percent. Normal duty cycle is between 4-96 percent. The signal circuit is an input to the body control module (BCM). If the duty cycle is outside of the normal range, DTC B1516 08 sets. The BCM also tests for correct polarity of the sensor. If the BCM detects positive current flow with the engine OFF, DTC B1516 66 sets.
The body control module (BCM) has 2 circuits for monitoring vehicle 12V system voltage. The BCM B+ is supplied to terminal 3 X3 by the BCM fuse, and the high resolution B+ is supplied to the BCM terminal 10 X4 by the IPC fuse. The BCM monitors the system voltage on both circuits to ensure that the voltage stays within the proper range. Damage to components, and incorrect data may occur when the voltage is out of range. If the BCM detects the system voltage on the high resolution B+ circuit is outside the normal range, DTC B1517 will set.
The body control module (BCM) monitors the state of charge (SOC) of the 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 power steering control module (PSCM) monitors the 12V system voltage to make sure that the voltage stays within the proper range. Damage to components, and incorrect data input can occur when the voltage is out of range. The PSCM monitors the system voltage. If the PSCM detects a 12V system voltage outside an expected range, DTC C0800 will set.
Twelve volts is supplied to the electronic suspension control (ESC) module by the battery positive (B+) voltage circuit. The ESC module monitors the supplied voltage to determine if it is within a valid operating range. Damage to components, and incorrect data may occur if the voltage is out of range. The ESC module disables all outputs, and sets DTC C0895 00, if high or low 12V battery voltage is detected.
The accessory DC power control module (APM) supplies 42 volts to the power steering control module (PSCM). The PSCM monitors the supplied intermediate voltage to determine if it is within a valid operating range. Damage to components, and incorrect data may occur if the voltage is out of range. The PSCM disables power assist and sets DTC C0895 if high or low intermediate voltage is detected.
The electronic brake control module (EBCM) monitors the 12 V system voltage to make sure that the voltage stays within the proper range. Damage to components, and incorrect data input can occur when the voltage is out of range.
The electronic brake control module (EBCM) monitors the 12 V battery positive (B+) voltage. If the voltage level is too high, damage may result in the system. When a high voltage condition is detected the EBCM turns OFF the system relay which removes 12 V battery voltage from the solenoid valves and pump motor, and DTC C0900 sets.
The engine control module (ECM) monitors the 12V battery positive (B+) 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 ECM detects low 12V battery voltage, then DTC P0562 will set.
The engine control module (ECM) monitors the 12V system voltage to ensure that the voltage stays within the proper range. Damage to components, and incorrect data may occur when the voltage is out of range.
Description and Operation
Charging System Description and Operation
Electrical Information Reference
- «Circuit Testing»(ref-364488-S04114729552010063000000)
- «Connector Repairs»(ref-364488-S23771656832010063000000)
- «Testing for Intermittent Conditions and Poor Connections»(ref-364488-S16423338542010063000000)
- «Wiring Repairs»(ref-364488-S17530456672010063000000)
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.
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.
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.
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
- It monitors the battery voltage and estimates the battery condition.
- It takes corrective actions by adjusting the regulated voltage.
- It performs diagnostics and driver notification.
The battery condition is estimated during ignition off and during ignition on. During ignition off the state-of-charge (SOC) of the battery is determined by measuring the open-circuit voltage. The SOC is a function of the acid concentration and the internal resistance of the battery, and is estimated by reading the battery open circuit voltage when the battery has been at rest for several hours.
The SOC can be used as a diagnostic tool to tell the customer or the dealer the condition of the battery. Throughout ignition-on, the algorithm continuously estimates SOC based on adjusted net amp hours, battery capacity, initial SOC, and temperature.
While running, the battery degree of discharge is primarily determined by a battery current sensor, which is integrated to obtain net amp hours.
In addition, the EPM function is designed to perform regulated voltage control (RVC) to improve battery SOC, battery life, and fuel economy. This is accomplished by using knowledge of the battery SOC and temperature to set the charging voltage to an optimum battery voltage level for recharging without detriment to battery life.
Charging System Operation
The purpose of the charging system is to maintain the battery charge and vehicle loads. There are 6 modes of operation and they include
- Battery Sulfation Mode
- Normal Mode
- Fuel Economy Mode
- Headlamp Mode
- Voltage Reduction Mode
- Plant Assembly Mode
Charge Indicator Operation
The instrument panel cluster (IPC) illuminates the charge indicator and displays a warning message in the driver information center (DIC) when the one or more of the following occurs
- The engine control module (ECM) detects system voltage less than 11 volts or greater than 16 volts. The IPC receives a GMLAN message from the ECM requesting illumination.
- The BCM determines that the system voltage is less than 11 volts or greater than 16 volts.
- The IPC receives a GMLAN message from the body control module (BCM) indicating there is a system voltage range concern.
- The IPC performs the displays test at the start of each ignition cycle. The indicator illuminates for approximately 3 seconds.
- The ignition is ON, with the engine OFF.
Battery Voltage Gauge Operation
The IPC displays the system voltage as received from the BCM over the GMLAN serial data circuit. If there is no communication with the BCM then the gauge will indicate minimum.
This vehicle is equipped with a regulated voltage control (RVC) system. This will cause the voltmeter to fluctuate between 12 and 14 volts, as opposed to non-regulated systems which usually maintain a more consistent reading of 14 volts. This fluctuation with the RVC system is normal system operation and NO repairs should be attempted.
Starting System Description and Operation
The HP2 hybrid system does not use a conventional starter. Refer to Hybrid Modes of Operation Description for information about the starting system.