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. The monitoring method for this sensor is to check the (-) side signal of the sensor circuit when a reference voltage is applied to (+) side of the sensor circuit. 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 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(RR) ? Faulty HECU |
Case1 (Large Air-Gap) | Detect Mode | ? Outside the ABS control cycle ? Diagnosis mode ? Failure mode |
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 154msec, Otherwise, if their difference beyond 4Km/h or >0.4g is continued for 120 seconds. ? 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 5sec. Otherwise, In >0.4g, the condition is 120 seconds. - This monitoring is performed for the period that the minimum velocity rises from 2km/h to 10km/h. |
Case2 (Long Term ABS mode) | Detect Mode | ? Inside the ABS control cycle. |
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. |
Fail Safe | ? Sensor failure outside the ABS control cycle 1. Only one wheel failure : Only the ABS(TCS) function is inhibited. The ABS(TCS) warning lamp is activated and the EBD warning lamp is not activated. 2. More than two wheels failure : System down. Both the ABS(TCS) and the EBD function are inhibited and the ABS and the EBD warning lamps are activated. In this failure, the valve relay and all solenoids are prevented from being switched on. ? 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 controller completes the ABS control, only the ABS(TCS) function is inhibited. The ABS(TCS) warning lamp is activated and the EBD warning lamp is not activated. 2. One rear wheel failure : Inhibit ABS control of both front wheels and the pressure of both rear wheels is decreased. After the controller completes the ABS control, only the ABS(TCS) function is inhibited. The ABS(TCS) warning lamp is activated and the EBD warning lamp is not activated. 3. More than two wheels failure : System down. Both the ABS(TCS) and the EBD function are inhibited and the ABS(TCS) and the EBD warning lamps are activated. In this failure, the valve relay and all solenoids are prevented from being switched on. |
Schematic Diagram