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. The wheel speed sensor generates sinewave signals, based on magnetic field made by a permanent magnet in the speed sensor, when the tone wheel rotates. The frequency and AC voltage changes in proportion to the wheel speed, and the HECU determines the speed by calculating the frequeny of the signal.
DTC Description
The ABS ECU monitors the wheel speed sensor signal continuously.
This code is set if an abnormal speed change ratio is detected or signal isn’t detected while the vehicle speed is more than 20Km/h .
Warning lamp is turned OFF if the detected fault is not exist when the IG KEY is turned to ON again, and wheel speeds are more than 20 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(FR) ? Faulty HECU |
Detect Mode | ? Outside the ABS control cycle ? Inside the ABS control cycle ? Inside the EBD control cycle |
Enable Conditions | ? When ECU detects sharp change of wheel velocity (that is over 30km/h per 7ms), ECU starts to use extrapolated velocity until extrapolated velocity reaches measured velocity. If ECU detects following condition while using extrapolated velocity, ECU decides the sensor failure. - During Vref>20km/h, there is no pulse input from this wheel sensor continuously 301ms. But when Vref<20km/h, ECU clears time counter.. - If there is input pulse from this wheel sensor, ECU starts to count the times of sharp velocity change (that is over 30km/h per 7ms). And ECU counts 5 times. But when ECU finishes extrapolating calculation, ECU resets the counter. ? Vref : Estimated vehicle velocity |
Fail Safe | ? Sensor failure outside of the ABS control cycle, inside of the EBD control cycle. 1. Only one wheel failure : Only the ABS function is inhibited. The ABS warning lamp is activated and the EBD warning lamp is not activated. 2. One rear wheel or over two wheels failure : System down. ? Sensor failure inside the ABS control cycle 1. One front wheel failure : HECU discontinues ABS control of defect wheel and continues ABS control of normal wheels. ABS inhibit after end of ABS control. The ABS warning lamp is activated and the EBD warning lamp is not activated. 2. Two front wheels failure : HECU discontinues ABS control of defect wheel and continues ABS control of normal wheels. System down after end of ABS control. 3. One rear wheel failure : HECU continues ABS control of rear wheels using information of normal rear wheel and front wheels. System down after end of ABS control 4. Two rear wheels failure : System down. 5. One front wheel and one rear wheel failure : HECU discontinues ABS control of defect front wheel, and continues rear wheels using information of normal rear wheel. System down after end of ABS control. 6. Over three wheels failure : System down. |
Specification
Sensor Type | Offset Voltage | Internal Resistance | The Number of Tooth | Airgab |
Coil Type | 0.4V ~ 2.7V | 1.1 ? ± 550 O | 54T | 1.0~1.6mm |
Schematic Diagram
Signal Waveform