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.
The ABS ECU monitors the wheel speed sensor circuit continuously. If the sensor signal current is continuously out of the specified range for 140msec, then the HECU determines that the circuit is open/short, and sets this code. 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.
Item | Detecting Condition | Possible cause |
DTC Strategy | ● Current Monitoring | ● Open or short of Wheel speed sensor circuit(FL) ● Faulty Wheel speed sensor(FL) ● Faulty HECU |
Detect Mode | ● Initial Check ● Outside the ABS control cycle ● Inside the ABS control cycle ● Diagnosis mode ● Failure mode | |
Enable Conditions | ● When the sensor signal current is continuously out of the specified range of 4 mA ± 10% ~ 22 mA ± 10% for 140msec. | |
Fail Safe | ● Sensor failure outside of the ABS control cycle 1. Only one wheel failure : Only the ABS/TCS/ESP functions are inhibited. The ABS/TCS/ESP warning lamps are activated and the EBD warning lamp is not activated. 2. More than two wheels failure : System down. The ABS/EBD/TCS/ESP functions are inhibited. The valve relay and all solenoids are prevented from being switched on. The ABS/EBD/TCS/ESP warning lamps are activated. ● Sensor failure inside the ABS control cycle 1. One front wheel failure : Inhibit the ABS/TCS/ESP control of the failed-wheel and maintain the ABS/TCS/ESP control of normal wheel. After the ABS/TCS/ESP control, the ABS/TCS/ESP functions are inhibited. The ABS/TCS/ESP warning lamps are activated and the EBD warning lamp is not activated. 2. Failure at one rear wheel : ABS/TCS/ESP control of both front wheels are inhibited and the pressure of both rear wheels are decreased. After the controller completes the ABS/TCS/ESP control, the ABS/TCS/ESP functions are inhibited. The ABS/TCS/ESP warning lamps are activated and the EBD warning lamp is not activated. 3. More than 2 wheels failure : System down. The ABS/EBD/TCS/ESP functions are inhibited. The valve relay and all solenoids are prevented from being switched on. The ABS/EBD/TCS/ESP warning lamps are activated. |
