EPS Indicator
Under normal conditions, the EPS indicator (A) comes on when the ignition switch is turned to ON (II), then goes off after the engine is started. This indicates that the bulb and its circuit are operating correctly. If there is a failure in the system after the engine is started, the EPS indicator will stay on, and the power assist is turned off or restricted.
Scheme 98
When the EPS indicator comes on, the control unit memorizes the DTC. In this case, the control unit will not activate the EPS system after the engine starts again, but it keeps the EPS indicator on. When DTC 11,12, or 13 is stored in the control unit, the EPS indicator will stay on until the DTC is erased. Even though the system is operating normally, the EPS indicator will come on under the following conditions
- When the vehicle is barely moving, 1 mph (1 km/h) or stopped, and the engine speed is 2,000 rpm or more for about 3 minutes.
- When the engine speed is 500 rpm or less, and the vehicle is traveling at a speed of 6.2 mph (10 km/h) or more for about 3 minutes.
To determine the actual cause of the problem, question the customer about the conditions during which the problem occurred, taking the above conditions into consideration.
How to Clear DTCs Using the Service Check Signal Circuit Method
Note. Use this procedure when the HDS software does not match the year/model vehicle you are working on.
Scheme 99
- With the ignition switch in LOCK (0), connect the HDS to the data link connector (DLC) (A) located under the driver's side of the dashboard.
- With the vehicle on the ground, set the front wheels in the straight ahead driving position.
- Short the SCS circuit to body ground using the HDS.
- Turn the steering wheel 45 degrees to the left from the straight ahead driving position, and hold the steering wheel in that position.
- Turn the ignition switch to ON (II). The EPS indicator comes on, then it goes off after 4 seconds.
- Within 4 seconds after the EPS indicator goes off, return the steering wheel to the straight ahead driving position and release the steering wheel. The EPS indicator comes on again 4 seconds after releasing the steering wheel.
- Within 4 seconds after the EPS indicator comes on, turn the steering wheel 45 degrees to the left again and hold it in that position. The EPS indicator goes off after 4 seconds.
- Within 4 seconds after the EPS indicator goes off, return the steering wheel to the straight ahead driving position again and release the steering wheel. The EPS indicator blinks twice 4 seconds after releasing the steering wheel, indicating that the DTC was erased. NOTE: If the EPS indicator does not blink twice, an error was made in the procedure and the DTC was not erased. Turn the ignition switch to LOCK (0), and repeat the operation from step 3.
- Turn the ignition switch to LOCK (0) within 5 seconds after the EPS indicator blinks twice. NOTE: If the ignition switch is not turned to LOCK (0) within 5 seconds after the EPS indicator blinks, the system will go to the memorizing mode of the torque sensor neutral position. To avoid this, turn the steering wheel 45 degrees to left from the straight ahead driving position and turn the ignition switch to LOCK (0). This will return the system to the alert mode.
- Disconnect the HDS from the DLC.
- Recheck for the DTC to be sure it has been erased.
Scheme 100
EPS System Outline
The power steering system adopts the electric power steering assisting for the control force of the steering wheel in the driving force of the electric motor.
The EPS control unit is doing an appropriate steering force control according to the running situation of the vehicle (at time of low speed, lightness, by the control of emphasis and high-speed running time, control with the steady weigh and the control which will be switched from low speed to high speed smoothly later) by the ESP motor.
The EPS control unit is designed for use with an automotive power steering for the primary purpose of controlling the assist motor (brush less motor) for the power steering by using as inputs the steering torque signals received from the "steering torque sensor" installed in the steering gearbox as well as the speed signals received from the "vehicle speed sensor" installed in the vehicle. In addition to the above function, the EPS control unit also provides the failsafe function, self diagnosis function and motor output limiting function.
Scheme 101
Steering gearbox
Assist motor rotates outer of the rack shaft, and transmits the assistance power directly to the rack shaft. The transmission mechanism adopts the ball screw, and has raised the transmission efficiency.
Scheme 102
Circuit Diagram
'00-03 models
Scheme 103
Scheme 104
'04-09 models
