Specifications

Chassis Specialist : Electric Power Steering
Page 8
Operation and Diagnosis
In this section the various EPS systems will be discussed. This section will be broken down by vehicle
manufacturer—Ford, General Motors, Honda and Toyota.
FORD ELECTRIC POWER STEERING ASSIST SYSTEM (EPAS)
Ford refers to the electric power steering system as Electronic Power Assist Steering or EPAS. The
system consists of a steering column which contains the power steering control module (PSCM), the
electric motor, the torque sensor and a steering gear coupled with an intermediate shaft. This system
does not use a steering wheel position sensor unless the vehicle is equipped with the Electronic
Stability Programme (ESP). The PSCM determines the necessary assist based on input from the torque
sensor as well as the suspension and tire information programmed into the module. The steering wheel
torque sensor uses dual analogue sensors to inform the PSCM which direction the steering wheel is
being turned. If the steering wheel is turned to the left, the left signal increases while the right signal
decreases. The opposite occurs when the steering wheel is turned to the right, the right signal increases
and the left signal decreases. The system will operate when the vehicle’s system voltage is between 10
and 16 volts.
Power to the EPS system is provided via an 80 amp fuse, used to power the EPS motor, and a 10 amp
fuse, used to power the PSCM. The PSCM uses the vehicle high speed CAN bus for vehicle speed
information. Diagnostic trouble codes can be accessed using a scan tool. When a trouble code is set the
PSCM will request the instrument panel (IPC) to illuminate the service steering soon light or message.
The following are the trouble codes the system will set
DTC
Description
B1317
Battery Voltage High
B1318
Battery Voltage Low
B1342
Internal ECU Fault
B2277
Electric Power Steering Motor Malfunction
B2278
Steering Shaft Torque Sensor Malfunction