Hybrid Control Module (HCM)

The hybrid control module (HCM) is located on the engine fan shroud near the powertrain control module (PCM). It acts as a gateway between the high-speed GMLAN and Class 2 local area networks. If a module in the high-speed system needs to pass information to the Class II bus, it tags that message and passes it on to the HCM; the HCM reads the message and passes it along to the appropriate network. For example, if the starter generator control module (SGCM) needs to display a warning or alert the driver to a change in operating mode, the HCM would take that message from the high speed link and pass it to the display controller, which is on the Class II system. The HCM also:

• Controls automatic engine starts and stops
• Controls the energy flowing into/out of the 14-volt and 42-volt batteries
• Enables and disables power for the auxiliary power outlets
• Enables and disables surge smoothing/active damping
• Disables energy generation after airbag deployment
• Controls the auxiliary transmission pump, the power maintenance relay, and the auxiliary heater pump
• Controls starter generator speed during transmission downshift assists-The downshift assists support the engine during un-fueled downshifts from 4th to 3rd gear and 3rd to 2nd gear. The HCM calculates a target engine speed and uses the starter generator to maintain that target. The starter generator has to control engine speed, using a torque command, which is within the upper and lower torque limits specified by the HCM.