Electric power steering uses an electric motor to assist the steering. A computer module (ECU) receives information from several sensors and decides which level of assistance the electric motor should deliver to the steering. When you install an electric power steering set up to your vehicle without a steering controller unit, it will not work as the ECU doesn’t receive information from the vehicle and engine speed sensor. These are not often fitted to the older vehicles and that’s why you need a steering controller unit; it sends the relevant information to the steering ECU. Therefore, without this, an electric power steering system will not work.