C1204 Wheel Speed Sensor Front RH Range / Performance - Automotive Repair Guides & Equipment

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 reference 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 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 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

Current Monitoring

Open or short of Wheel speed sensor circuit

Faulty Wheel speed sensor

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

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

TERMINAL AND CONNECTOR INSPECTION

1.	Many malfunctions in the electrical system are caused by poor harness(es) and terminal condition. Faults can also be caused by interference from other electrical systems, and mechanical or chemical damage.

2.	Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage.

Has a problem been found?

	▶ Repair as necessary .
	▶ Go to “Power Circuit Inspection” procedure.

POWER CIRCUIT INSPECTION

■ Open or Short Check

1.	Ignition “ON” & Engine “OFF”.

Measure voltage between power terminal of the wheel speed sensor harness connector and chassis ground.

Specification : Approx. B+

Is the measured value within specifications?

	▶ Go to “Signal Circuit Inspection” procedure.
	▶ Repair open or short in power circuit between HECU harness connector and wheel speed sensor harness connector .

SIGNAL CIRCUIT INSPECTION

■ Wheel speed sensor circuit check

1.	Lift the vehicle.

2.	Ignition “ON” & Engine “OFF”.

3.	Turn the wheel by hand.

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

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

Is the measured waveform within specifications?

	▶ Go to “Component Inspection” procedure.
	▶ Repair open or short in signal circuit between HECU harness connector and wheel speed sensor harness connector

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.

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

Is the measured waveform within specifications?

	▶ Fault is intermittent caused by poor connection in wheel speed sensor harness (FR). .
	▶ 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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