Generator Control Module

The generator control module, also referred to as the starter generator control module, is a serviceable GMLAN device located under the hood, toward the front of the vehicle on the drivers side. It is connected to the vehicles 12 and 36-volt DC power circuits, and it is also joined to the starter-generator by 3-phase AC cables. The generator control module is cooled by engine coolant, which is circulated through a cold plate. A separate, electrically driven pump is used to ensure adequate coolant flow, and individual coolant inlet and outlet hoses connect the cold plate to the cooling system. The generator control module performs 3 main functions:

1. As the power inverter for the starter-generator, the generator control module converts 36-volt DC power into 3-phase AC power to drive the starter-generator as a motor. The power inverter also rectifies 36-volt AC output power from the starter-generator into the 36-volt DC power used to charge the 36-volt generator battery.
2. An auxiliary power module contained within the generator control module converts 36 volt DC power into the 12-volt DC power which is used for 12-volt vehicle loads and to charge the underhood 12-volt battery. A serviceable 175-Amp Fuse (GM P/N 15305191) located beneath the generator control module DC cable terminal box cover protects the vehicles 12-volt electrical system from excessive current.
3. The generator control module contains a Renesas M32 processor, and it directly controls the starter-generator, transmission auxiliary oil pump, hill-hold solenoids, auxiliary coolant pump and the generator control module coolant pump. The pumps and solenoids are driven by 12-volt pulse width modulated (PWM) power through vehicle wiring harnesses.