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 three 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.