Charging System Operation: Notes

WARNING: This page is about a different car, the 2008 Buick LaCrosse and 2008 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.

The purpose of the charging system is to maintain the battery charge and vehicle loads. There are 6 modes of operation and they include:

Charge Mode
Fuel Economy Mode
Voltage Reduction Mode
Start Up Mode
Windshield Deice Mode
Battery Sulfation Mode

The ECM/PCM controls the generator through the generator field control circuit. It monitors the generator performance through the generator field duty cycle signal circuit. The signal is a 5 volt PWM signal of 128 Hz with a duty cycle of 0-100%. Normal duty cycle is between 5-95%. Between 0-5% and 95-100% are for diagnostic purposes. The following table shows the commanded duty cycle and output voltage of the generator:

Commanded Duty Cycle	Generator Output Voltage
10 %	11.0 V
20 %	11.56 V
30 %	12.12 V
40 %	12.68 V
50 %	13.25 V
60 %	13.81 V
70 %	14.37 V
80 %	14.94 V
90 %	15.5 V

The generator provides a feedback signal of the generator voltage output through the generator field duty cycle signal circuit to the ECM/PCM, this information is sent to the BCM. The signal is a 5 volt PWM signal of 128 Hz with a duty cycle of 0-100%. Normal duty cycle is between 5-99%. Between 0-5% and 100% are for diagnostic purposes.