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 signal continuously.
This code is set if an abnormal speed change ratio is detected while the vehicle speed is more than 2Km/h.
Warning lamp is turned OFF if the detected fault is not more than when the IG KEY is turned to ON again, and wheel speeds are more than 10 Km/h.
DTC Detecting Condition
Item | Detecting Condition | Possible cause |
DTC Strategy | Signal monitoring
| Improper installation of wheel speed sensor
Abnormal Rotor and wheel bearing
Faulty Wheel speed sensor (RL)
Faulty HECU
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Case1 (LargeAir-Gap) | Detect Mode | Outside the ABS control cycle
Diagnosis mode
Failure mode
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Enable Conditions | When the minimum wheel velocity is 2km/h and the velocity of other wheels exceed 10km/h with the acceleration of < 0.4g, the controller start comparing the velocity of other wheels except the min. wheel. if their difference below 4km/h is continued for 140msec, Otherwise, if their difference beyond 4km/h or >0.4g is continued for 2 minutes.
In < 0.4g, when the velocity of more two wheels is 2km/h and the max. wheel velocity exceeds 10km/h, the condition is continued for 20 sec. Otherwise, In >0.4g, the condition is 2 minutes.
After velocity of 4 wheel exceeds 10km/h, when velocity of 1 wheel or 2 wheel is 2km/h and difference of other 2 wheel velocity is less than 4km/h under that those velocity is more than 10km/h, if that conditions are continued for 12 seconds. '- This monitoring is performed for the period that the minimum velocity rises from 2km/h to 10km/h.
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Case2 (long term ABS mode) | Detect Mode | Inside the ABS control cycle
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Enable Conditions | During the ABS control cycle, if the wheel velocity of 2km/h is lasted for more than 12sec.
If the ABS control cycle is continued for more than 36sec.
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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. More than two wheels failure : System down. The ABS/EBD functions are inhibited. The valve relay and all solenoids are prevented from being switched on. The ABS/EBD warning lamps are activated.
Sensor failure inside the ABS control cycle 1. One front wheel failure : Inhibit the ABS control of the failed-wheel and maintain the ABS control of normal 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. Failure at one rear wheel : ABS control of both front wheels are inhibited and the pressure of both rear wheels are decreased. After the controller completes 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 2 wheels failure : System down. The ABS/EBD functions are inhibited. The valve relay and all solenoids are prevented from being switched on. The ABS/EBD warning lamps are activated.
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Specification
SensorType | Output Voltage | The Number of Tooth | Airgab |
HIGH | LOW |
Hall IC | 1.4V | 0.7V | 48T | 0.2~2.0mm |
Diagnostic Circuit Diagram
Signal Waveform & Data
Fig 1) Normal waveform of wheel speed sensor (Active type)