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.
The Wheel Speed Sensors are active hall-sensor type.
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 unless additional faults are detected when the IG KEY is turned ON again, and wheel speed is more than 10 Km/h.
Item | Detecting Condition | Possible cause | |
DTC Strategy |
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Signal monitoring | 1. Improper installation of wheel speed sensor 2. Abnormal Rotor and wheel bearing 3. Faulty Wheel speed sensor | |
Enable Conditions | Case1 (Speed jump) |
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Controller counts the number of the wheel acceleration of 100g[(25km/h) for 7ms]. When the numbers at one wheel exceed 56 times, or When the numbers at more two wheels exceed 5 times, controller recognize the failure
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Controller counts the number of the wheel acceleration of 70g[(17.5km/h) for 7ms]. When the numbers at one wheel exceed 126 times, or When the numbers at more two wheels exceed 20 times, controller recognize the failure
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Controller counts the number of the wheel deceleration of -100g[(-25km/h) for 7ms]. When the numbers at each wheel exceed 56 times, controller recognize the failure
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The wheel deceleration of –100g[(-25km/h) for 7ms] causes the controller to start monitoring this failure and to compare the wheel velocity with the vehicle velocity from next cycle. When its difference of -100g is continued for more than 140msec, controller recognize the failure
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In case that any sensor failure at other wheel was already detected, When the numbers of 100g at each wheel exceed 5 times, or When the numbers of 70g at each wheel exceed 20 times, controller recognize the failure - The counter of speed jump is cleared every 30min. - This monitoring is performed for the period that the velocity of each wheel exceeds 2km/h. | |
Case2 (wrong exciter) |
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Max. wheel velocity exceeds 20km/h and the wheel velocity is 40% of max. wheel velocity. if this condition is lasted for 2 minutes
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Max. wheel velocity exceeds 40km/h and the wheel velocity is 60% of max. wheel velocity. if this condition is lasted for 2 minutes | ||
Fail Safe | 1) Only one wheel failure : Inhibit the ABS/ESP/DBC control, allow the EBD control. The ABS/ESP/DBC warning lamps are activated, the EBD warning lamp is not activated 2) More than two wheels failure : The ABS/EBD/ESP/DBC functions are inhibited. The ABS/EBD/ESP/DBC warning lamps are activated | ||
Sensor Type | Output Voltage | Air Gap | |
HIGH | LOW | ||
Active Type | 1.4V | 0.7V | 0.4~1.5mm |
Fig.1) Normal waveform of wheel speed sensor with low speed condition
- High : approx. 1.4V, Low : approx. 0.7V
Fig.2) Normal waveform of smart type wheel speed sensor with standing still
※ Smart type wheel speed sensor is applied to the rear wheel speed sensor of the vehicle equiped SPAS.
Fig.3) Normal waveform of smart type wheel speed sensor with moving condition.
