GM Service Manual Online
For 1990-2009 cars only

The starter/generator control module (SGCM) cooling system description and operation is divided into three areas:

    • SGCM Cooling System Components
    • SGCM Cooling System Operation
    • SGCM Cooling System Coolant Cycle

SGCM Cooling System Components

SGCM

The starter/generator control module (SGCM) is a GMLAN device. The SGCM monitors 3 coolant temperature sensors that are mounted in the coolant stream, 4 coolant level sensors that are mounted in the electronics coolant of the SGCM, the SGCM coolant pump relay control circuit, and the SGCM coolant fan relay control circuit to maintain its internal cooling requirements. Internal to the SGCM are the electronics that control the system voltage, these electronic components are immersed in a coolant. This coolant is not the coolant that is circulated though the coolant circuit, the coolant helps evenly distribute the heat of the electronics and are monitored by the 4 coolant level sensors.

SGCM Coolant Pump

The SGCM coolant pump is controlled through a relay by the SGCM. The SGCM coolant pump circulates the coolant through the SGCM cooling system.

SGCM Coolant Fan

The SGCM coolant fan is controlled through a solid state relay by the SGCM. The SGCM coolant fan is a puller type fan that draws air through the SGCM radiator.

SGCM Cooling System Operation

The purpose of the starter/generator control module (SGCM) coolant system is to cool the SGCM internal electronics. The SGCM commands the SGCM the SGCM coolant pump and coolant fan ON or OFF at the following temperatures:

    • Coolant pump from OFF to ON at 60°C (140°F)
    • Coolant pump from ON to OFF at 55°C (131°F)
    • Coolant fan from OFF to low speed at 75°C (167°F)
    • Coolant fan from low speed to high speed at 80°C (176°F)
    • Coolant fan from high speed to low speed at 75°C (167°F)
    •  Coolant fan from low speed to OFF at 70°C (158°F)

SGCM Cooling System Coolant Cycle

The starter/generator control module (SGCM) coolant is a 50/50 mixture of DEX-COOL antifreeze and clean, drinkable water. The coolant is drawn from the SGCM coolant tank by the SGCM coolant pump. The coolant pump then forces the coolant through the SGCM coolant radiator. The coolant then is sent to the SGCM to cool the SGCM electronics.