When a hybrid vehicle is equipped with the hill start assist feature, the engine may shutoff when the vehicle is stopped on an incline. 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 (ECU'S) are required in order to accomplish a safe smooth transition during the vehicle start and stops:

The hill start assist feature minimizes vehicle rolling during the transition between brake release and engine restart. The brake pressure valves maintain pressure in the brake lines, even thought the brake pedal is released, until the engine starts. Brake pressure is then released following engine restart.

The valves are actuated through the EBCM based on a calculated grade. The EBCM also commands the brake light signal required to the BCM during the transition between engine off, and engine start.

The IPC receives a serial data message and displays The "SRVC HILL START" on the DIC when the EBCM detects a condition that affects the hill start assist system. In the event of other failures which prevent Hill Start Assist operation the EBCM shall set the appropriate DTC.