Hello Paul, I own a Toyota Mark X whose steering periodically gets hard. It all started when I hit a big hump at high speed. However, currently, whenever an EPS light goes on the dashboard, the steering becomes stiff. What could be the cause and solution because we have tried replacing the steering rack but it has not helped. Bamwine.
Hello Bamwine, your Toyota may have intermittent failure of EPS - Electric Power Steering system. The EPS is electrically powered steering which is designed to reduce energy loss or the amount of effort needed to steer your vehicle.
Unlike the conventional hydraulic steering systems, EPS uses the body control module (BCM), power steering control module (PSCM), a torque sensor and EPS motor.
These components rely on the car system voltage to run and a serial data bus to communicate between each other and the message centre. The EPS motor is built into the steering column and not the steering rack.
Inspection of this system is best done with a computer diagnostic tool which will interrogate the system to identify whether it is component or circuit failure.
Common causes of breakdown include relay or fuse failure or broken circuit due to a loose or damaged connector. Mechanical damage of the steering column after an accident can cause failure of the EPS. Get a good technician to inspect this for you.