Steering (Operation): Description and operation (page 2 of 3)

EPAS electrical operation

EPAS ECU (EPAS1 ECU shown)

1. Torque sensor
2. Main
3. Sub
4. Speed sensor
5. Engine revolution sensor
6. Ignition switch supply
7. Battery supply
8. Earth
9. Interface

On EPAS1 vehicles (up to 2000MY), the torque sensor has two potentiometers. Each potentiometer has its own power supply and earth connection and operate in opposing directions. The ECU monitors the output from each potentiometer and can suspend power assistance and illuminate the EPAS warning lamp if a fault is detected.

10. Main control computer
11. Fail safe relay
12. Motor drive circuit
13. Current control circuit
14. Clutch drive circuit
15. Motor
16. Clutch
17. Warning lamp

On EPAS2 vehicles (from 2000MY), the torque sensor has two potentiometers. The potentiometers share a power supply and earth connection from the ECU and operate the same direction. One potentiometer provides the torque data and the other potentiometer acts as a fault monitor. The ECU checks the output from each potentiometer and will illuminate the EPAS warning lamp and suspend power assistance whilst the fault is present.