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HOMESERVICE MANUALSPONTIAC2008GRAND PRIX BASEREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 407 (BATTERY, CHARGING SYSTEM AND STARTING SYSTEM)DESCRIPTION AND OPERATIONCHARGING SYSTEM DESCRIPTION AND OPERATIONCHARGING SYSTEM OPERATIONNOTES
2008 Pontiac Grand Prix Base

Charging System Operation: Notes

2008 Pontiac Grand Prix BaseSECTION 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.

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