1. Wheel Speed Sensor
The wheel speed sensor is the essential component the ABS ECU uses to calculate vehicle speed and to determine whether wheel lock occurs.
For example, rear wheel speed signal is used as a referecnce value, for vehicle speed, in front wheel drive vehicles, and if a difference between front and rear wheel speed occurs, then ABS control is performed.
Wheel speed sensor is active hall-sensor type.
The ABS ECU monitors the wheel speed sensor circuit continuously.
A direct current is supplied in the wheel speed sensor by a power source in the input amplifier of the control unit.
If the WSS circuit is broken, in that case a fault is detected by detecting abnormal input current. HECU cuts off the voltage supply to wheel sensor channel which had a fault and prevent vehicle's damage due to super heated harness.
If one or more defects has detected, DTC code of defected wheel will be stored. Mutual short between sensors is detected by executing self diagnosis successively at corresconding wheel when ignition ON.
Warning lamp is turned OFF unless additional faults are detected when the IG KEY is turned ON again.
Item
Detecting Condition
Possible cause
DTC Strategy
Current Monitoring
Open or short of Wheel speed sensor circuit(RL)
Faulty Wheel speed sensor(RL)
Monitoring Period
Continuous after power up
Enable Conditions
When the sensor current levels are out of permissible range(LOW : 7mA, HIGH : 14mA) for 200ms.
- Stop control right away if wheel speed sensor failure is detected during no control
Fail Safe
One or two wheel speed sensor fault
- Only the ABS/ESP functions are inhibited
- The ABS/ESP warning lamps are activated and the EBD warning lamp is not activated
More than 2 wheel speed sensor fault
- The ABS/EBD/ESP functions are inhibited
- The ABS/EBD/ESP warning lamps are activated
SensorType
Output Voltage
Air Gap
HIGH
LOW
Active Type
1.4~2.0V
0.7~1.0V
0.4~1.0mm