Specifications

Chassis Specialist : Electric Power Steering
Page 27
TOYOTA ELECTRIC POWER STEERING (EPS) SYSTEM
Toyota also uses a steering column with an electric assisting motor. Torque is generated through the
motor and a reducing gear installed in the steering column shaft. The EPS ECU monitors the vehicle
speed, the skid control ECU and torque sensor to determine the correct amount of assist to apply. The
assist level is adjusted so there is more assist at lower speeds and virtually no assist at high speed. The
torque sensor is part of the steering column assembly and converts the mechanical force applied to the
steering wheel to an electrical signal the EPS ECU can use. The sensor is the same design as the
Honda, Ford and GM units.
The EPS motor assembly is also similar to the other vehicles. Current is provided by the EPS ECU
based on the input signals from the torque sensor, vehicle speed and skid control information. The
motor contains a rotation angle sensor to fine tune the electric steering control. The sensor is a resolver
sensor which detects the rotation angle of the motor and relays the information back to the EPS ECU.
System diagnostic trouble codes can be read and cleared with a scan tool or through the DLC. To
access the trouble codes without the Toyota Intelligent Tester perform the following steps
 Using the correct terminals jump pins 4 and 13 of the DLC together, verify the ignition is OFF
 Turn the ignition switch ON with the engine OFF
 The trouble codes will be flashed by the EPS indicator located in the instrument panel
 Codes will be displayed after four seconds. The light will flash ON for 0.5 seconds followed by
another 0.5 seconds with the light OFF. This indicates the 10’s numbers. The 10’s numbers will
be followed by a 1.5 second pause before the single digit numbers. If there is a second or third
code the next code will be followed by a 2.5 second pause. All trouble codes are displayed in
ascending order. Refer to the illustration below.