Electronic Power Assist Steering (EPAS) System

Steering System



Electronic Power Assist Steering (EPAS) System

The Electronic Power Assist Steering (EPAS) system consists of the following components:

- Power Steering Control Module (PSCM) - the PSCM controls the functions of the EPAS system and communicates with other modules that are on the High Speed Controller Area Network (HS-CAN) bus. The PSCM is attached to the EPAS column assembly and is not available separately for service.
- Motor - the EPAS gear uses a 12-volt brushless, reversible motor, a worm gear and a reduction gear to control the steering effort. The motor is attached to the EPAS column assembly and is not available separately for service.
- Steering sensor - the steering sensor is used by the PSCM to determine force applied to, speed and direction of the steering wheel. This information is transmitted to other modules along the HS-CAN bus. The sensor is attached to the EPAS column assembly and is not available separately for service.
- Steering column shaft - the steering column shaft connects the EPAS column assembly to the steering gear and is available separately for service. Refer to Steering Column.
- Steering gear - the steering gear is a rack and pinion type gear, which is serviced as an assembly and is contained within a one-piece aluminum housing. The steering gear uses tie-rod ends to connect the gear to the wheel knuckles. The steering gear can be serviced separately from the EPAS column assembly, refer to Steering.
- Tie-rod ends - one inner and outer tie rod is located at each end of the steering gear and are available separately for service. Refer to Steering.

The EPAS system provides power steering assist to the driver by replacing the conventional hydraulic valve system with an electric motor coupled to the steering shaft. The motor is controlled by the PSCM which senses the steering effort through the use of a sensor mounted between the steering column shaft and the steering gear. Steering assist is provided in proportion to the steering input effort and vehicle speed.



Active Park Assist

Some vehicles may also be equipped with active park assist. The active park assist system is controlled by the Parking Aid Module (PAM) and, when activated, can detect a parking space and steer the vehicle into the space by sending commands to the PSCM (the driver still controls the throttle, brakes and transmission). The active park assist system is comprised of several systems/modules that work together to aid in parallel parking maneuvers, the presence of certain DTCs in any of those systems/modules may keep the active park assist system from being enabled or may disable the system if currently being used. Refer to Collision Avoidance and Parking Assist Systems for additional information on active park assist.