Component Location
General Description
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 and good at temperature and noise chariteristic. Digital wave is produced as tone wheel rotate according as hall sensor principle.
Frequency of duty wave is changed in proportion to rotation of tone wheel and HECU calculate vehicle speed by this frequency.
DTC Description
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 cut 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 corresponding wheel when ignition ON.
Warning lamp is turned OFF unless fault is detected any more when the IG KEY is turned ON again.
DTC Detecting Condition
Item | Detecting Condition | Possible cause |
DTC Strategy | ? Voltage monitoring | ? Open or short of Wheel speed sensor circuit(FR) ? Faulty Wheel speed sensor(FR) ? Faulty HECU |
Case1 | Monitoring Period | ? Once after power up. |
Enable Conditions | ? Shorts between WSS lines and shorts to UZ can be detected by switching single WSS channels in sequence. If there is an error after end of test, a failure is recognized. |
Case2 | Monitoring Period | ? Continuous |
Enable Conditions | ? When the sensor current levels are out of permissible range(LOW : 7mA, HIGH : 14mA) for 200ms. |
Fail Safe | ? Sensor failure outside of the ABS control cycle 1. Only one wheel failure - Only the ABS functions are inhibited. - The ABS warning lamps are activated and the EBD warning lamp is not activated. 2. Two wheels failure - Only the ABS functions are inhibited. - The ABS warning lamps are activated and the EBD warning lamp is not activated. 3. More than 3 wheels failure - System down. The ABS/EBD functions are inhibited. - The ABS/EBD warning lamps are activated. ? Sensor failure inside the ABS control cycle 1. One front wheel failure - Inhibit the ABS control. Pressure is increased on a front wheel, Pressure is decreased on a rear wheel. After the ABS control, the ABS functions are inhibited. - The ABS warning lamps are activated and the EBD warning lamp is not activated. 2. Two wheels failure - Inhibit the ABS control. Pressure is increased on a front wheel, Pressure is decreased on a rear wheel. After the ABS control, the ABS functions are inhibited. - The ABS warning lamps are activated and the EBD warning lamp is not activated. 3. More than 3 wheels failure - System down. The ABS/EBD functions are inhibited. - The ABS/EBD warning lamps are activated. |
Specification
Sensor Type | Output Voltage | The Number of Tooth | Airgab |
HIGH | LOW |
Hall IC | 1.05V | 0.525V | 47T | 0.4~1.0mm |
Schematic Diagram
Signal Waveform