When a conventional vehicle is stopped on a hill, the brakes will hold the vehicle in place until the brake pedal is released. When a hybrid vehicle is completely stopped on a hill, the engine may shut off. When the driver releases the brake pedal, the engine will restart, but the vehicle may have an increased tendency to roll during the restart sequence. Inputs and outputs from the following electronic control modules (ECUs) are required to accomplish a safe smooth transition during vehicle stops and starts:

The hill hold minimizes the vehicle rolling during the transition between brake release and engine restart. The ECM and EBCM work together to control the hill hold function. The ECM determines the brake pressure necessary from a brake pressure sensor on the brake line down stream of the master cylinder to hold or release the vehicle. The EBCM receives a serial data message from the ECM to apply or release the brake pressure to the front calipers through the BPMV.

The malfunction indicator lamp (MIL) is controlled by the starter generator control module (SGCM) and illuminates when the SGCM detects a condition that affects the vehicle hybrid or hill start control system.