Charging System

The charging system uses 2 communication lines between the PCM and the generator/voltage regulator. Both of these communication lines use PWM. The voltage setpoint is calculated by the PCM and communicated to the voltage regulator over the generator communication (GENCOM) line. The PCM sends the GENCOM command only when it is necessary to adjust the voltage setpoint. If the setpoint does not need to be changed, several seconds may elapse between PCM GENCOM commands. This normal operation appears in the PID as occasional bursts of pulse-width commands. The third pin on the voltage regulator, the "A" circuit pin, is a circuit dedicated to monitor or sense battery voltage. The generator communicates load and error conditions to the PCM over the generator monitor (GENMON) line.

The PCM simultaneously controls and monitors generator output. When the current consumption is high or the battery is discharged, the PCM raises engine speed as needed to increase generator output. The generator charges the battery and at the same time supplies power for all required electrical loads. The battery is charged more effectively at a higher voltage when the battery is cold and at a lower voltage when the battery is warm. The PCM uses a signal from the IAT sensor to adjust the charging voltage according to the battery temperature. The PCM also uses other inputs to control the charging system voltage such as the VSS and engine coolant temperature. The voltage setpoint is calculated by the PCM and communicated to the voltage regulator by the GENCOM circuit based on the needs of the vehicle and the conditions.

The PCM turns off the generator during cranking to reduce the generator load and improve cranking speed. Once the engine starts, the PCM slowly increases generator output to the desired voltage.

The PCM reports any charging system faults and sends a message through the High Speed Controller Area Network (HS-CAN) to the BCM. The BCM controls the charging system warning indicator by sending a message over the Medium Speed Controller Area Network (MS-CAN) to the IPC. The IPC then controls charging system warning indication based on the message from the PCM through the BCM. The status of the PCM charging system warning indicator and/or message is confirmed by viewing PCM PID generator fault indicator lamp (GENFIL). Any charging system fault detected by the PCM results in one or more Diagnostic Trouble Codes (DTCs) being set and the PID GENFIL having a status of On.

Under certain circumstances, the charging system may have a concern, but still charge the battery while the vehicle is running. GENCOM normally initiates charging, but with a fault in this circuit the generator operates in a default mode (approximately 13.5 volts), the IPC illuminates the charging system warning indicator, and a corresponding message is displayed.