C1201 Wheel Speed Sensor Front-LH Range / Performance / Intermittent

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 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.

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

Enable
Conditions

Case1

Max. wheel velocity exceeds 20km/h and the wheel velocity is 40% of max. wheel velocity. if this condition is lasted for 2 minutes.

Max. wheel velocity exceeds 40km/h and the wheel velocity is 60% of max. wheel velocity. if this condition is lasted for 2 minutes.

Case2

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.

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.

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.

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.

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.

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.

SPECIFICATION

Sensor Type	Output Voltage		Airgap
	HIGH	LOW
Active Type	1.18~1.68V	0.59~0.84V	0.5~1.5mm

DIAGNOSTIC CIRCUIT DIAGRAM

SIGNAL WAVEFORM & DATA

Fig 1) Normal waveform of wheel speed sensor (Active type)

– High : Approx. 1.4V, Low : Approx. 0.7V

COMPONENT INSPECTION

■ Wheel speed sensor circuit check

1.	Lift the vehicle.

2.	Ignition “ON” & Engine “OFF”.

3.	Turn the wheel by hand.

Measure waveform between signal terminal of the wheel speed sensor harness connector and chassis ground with osciloscope.

Specification : High : 1.18~1.68V , Low : 0.59~0.84V

Is the measured waveform within specifications?

	▶ Fault is intermittent caused by faulty HECU, wheel speed sensor or external noise, an interference between harnesses. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. Repair as necessary .
	▶ Check for improper installation of wheel speed sensor. If NG, repair as necessary and then go to “Verification of vehicle Repair” procedure. Check for damage of rotor teeth or wheel bearing. If NG, repair as necessary Substitute with a known-good Wheel speed sensor and check for proper operation. If problem is corrected, replace Wheel speed sensor

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