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.
DTC Description
The ABS ECU monitors the wheel speed sensor signal continuously.
This code is set when the sensor air gap is out of specified range or when the ABS control cycle is continued abnormally.
The HECU checks for air gap malfunctioning by monitoring the sensor signal at speeds between 2Km/h to 10 Km/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 (6.2mph).
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
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Case1 (Large Air-Gap) | Enable Conditions | When the minimum wheel velocity is 2km/h and the velocity of other wheels exceed 10km/h (6.2mph) 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 (2.5mph) is continued for 140msec, Otherwise, if their difference beyond 4km/h (2.5mph) or >0.4g is continued for 2 minutes. In < 0.4g, when the velocity of more two wheels is 2km/h (1.2mph) and the max. wheel velocity exceeds 10km/h (6.2mph), the condition is continued for 20 sec. Otherwise, In >0.4g, the condition is 2 minutes. After velocity of 4 wheel exceeds 10km/h (6.2mph), when velocity of 1 wheel or 2 wheel is 2km/h (1.2mph)and difference of other 2 wheel velocity is less than 4km/h (2.5mph) under that those velocity is more than 10km/h (6.2mph), if that conditions are continued for 12 seconds. - This monitoring is performed for the period that the minimum velocity rises from 2km/h (1.2mph) to 10km/h (6.2mph).
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Case2 (long term ABS mode) | Enable Conditions | During the ABS control cycle, if the wheel velocity of 2km/h (1.2mph) is lasted for more than 12sec. If the ABS control cycle is continued for more than 36sec.
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Fail Safe | Only one wheel failure : Inhibit the ABS/ESP control, allow the EBD control. The ABS/ESP warning lamps are activated, the EBD warning lamp is not activated. More than two wheels failure : The ABS/EBD/ESP functions are inhibited. The ABS/EBD/ESP warning lamps are activated.
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Specification
Sensor Type | Output Voltage | Airgap |
HIGH | LOW |
Active Type | 1.4V | 0.7V | 0.4~1.5mm |
Diagnostic Circuit Diagram
Signal Waveform & Data
Fig 1) Normal waveform of wheel speed sensor (Active type)
- High : Approx. 1.4V, Low : Approx. 0.7V