Vehicle Speed Functional Overview

The hybrid vehicle uses 3 methods to calculate vehicle speed.

Vehicle Speed From The Anti-Lock Brake System (ABS) Module -   The ABS module calculates wheel speed from the front 2 wheel speed sensors and sends this information to the PCM through the communication network.

Vehicle Speed From The Transaxle Control Module (TCM) -   The TCM calculates traction motor speed from the traction motor shaft speed sensor and combines it with (PCM stored) tire size and axle ratio data to determine vehicle speed. This calculation is then sent to the PCM over the communication network.

Vehicle Speed From Engine And Generator Speed -   The TCM calculates generator speed from the generator shaft speed sensor and sends this information to the PCM. The PCM combines input information from the generator speed and engine speed along with tire size and gear ratio to calculate a vehicle speed.

The PCM strategy then cross checks all the inputs to determine if they agree with one another. If there is a discrepancy between inputs, a vehicle speed fault flag is set in the PCM and a DTC is stored.