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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 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.

DTC Description

The ABS ECU monitors the wheel speed sensor signal continuously. This code is set when an abnormal signal due to air gap problem or an abnormal speed change ratio are detected at the vehicle speed between 10 km/h to 80 km/h. Warning lamp is turned OFF unless fault is detected any more when the IG KEY is turned ON again, and wheel speed is more than 12 Km/h.

DTC Detecting Condition

Item

Detecting Condition

Possible cause

DTC Strategy

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Signal monitoring

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Improper installation of wheel speed sensor

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Abnormal Rotor and wheel bearing

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Faulty Wheel speed sensor

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Faulty HECU

Case1

Monitoring Period

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The monitoring is active from 10 km/h to 80 km/h and if no ABS-control is active at a front wheel and a rear wheel.

Enable Conditions

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Every time, if a gap in the wheel speed sensor signal occurs cyclically with one wheel rotation, a fault counter is increased by one. If the fault counter exceeds its limit of 6, a wheel specific fault is stored in the EEPROM.

Case2

Monitoring Period

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Continuous

Enable Conditions

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If following interference and signal disturbance is detected, a failure is set after 10 s.

non-plausible high frequency received.

non-plausible high wheel acceleration.

non-plausible high wheel jurk.

non-plausible delta T and edges at low speed.

Fail Safe

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Sensor failure outside of the ABS control cycle

Only one wheel failure : Only the ABS/ESP functions are inhibited. The ABS/ESP warning lamps are activated and the EBD warning lamp is not activated.

Two wheels failure : Only the ABS/ESP functions are inhibited. The ABS/ESP warning lamps are activated and the EBD warning lamp is not activated.

More than 3 wheels failure :System down. The ABS/EBD/ESP functions are inhibited. The ABS/EBD/ESP warning lamps are activated.

●

Sensor failure inside the ABS control cycle

One front wheel failure : Inhibit the ABS/ESP control. Pressure is increased on a front wheel, Pressure is decreased on a rear wheel. After the ABS/ESP control, the ABS/ESP functions are inhibited. The ABS/ESP warning lamps are activated and the EBD warning lamp is not activated.

Two wheels failure : Inhibit the ABS/ESP control. Pressure is increased on a front wheel, Pressure is decreased on a rear wheel. After the ABS/ESP control, the ABS/ESP functions are inhibited. The ABS/ESP warning lamps are activated and the EBD warning lamp is not activated.

More than 3 wheels failure : System down. The ABS/EBD/ESP functions are inhibited. The ABS/EBD/ESP warning lamps are activated.

Monitor Scantool Data

Engine "ON".

Connect scantool to Data Link Connector(DLC).

Start and drive vehicle in gear and maintain vehicle speed is approx. 12 km/h or more(7 mph or more)

Monitor the "Wheel speed sensor" parameter on the Scantool.

Specification : Approx. 12 km/h or more (7 mph or more)

Is parameter displayed within specifications?

▶ Fault is intermittent caused by poor connection in wheel speed sensor harness and/or HECU's connector or was repaired and HECU memory was not cleared. Go to "Compont Inspection" procedure.

▶ 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 and then go to "Verification of vehicle Repair" procedure.

▶ Substitute with a known-good Wheel speed sensor and check for proper operation. If problem is corrected, replace Wheel speed sensor and then go to "Verification of Vehicle Repair" procedure.

▶ If OK, Go to "Component Inspection" Procedure.

COMPONENT INSPECTION

Ignition "OFF".

Engine "ON".

Start and drive vehicle in gear and maintain vehicle speed is approx. 12 km/h or more(7 mph or more).

Does warning lamp remain On?

▶ Substitute with a known-good HECU and check for proper operation. If problem is corrected, replace HECU and then go to "Verification of Vehicle Repair" procedure.

▶ Fault is intermittent caused by open or short of wheel speed sensor harness, faulty wheel speed sensor. Go to the applicable troubleshooting procedure.

Verification of Vehicle Repair

After a repair, it is essential to verify that the fault has been corrected.

Connect scantool and select "Diagnostic Trouble Codes(DTCs)" mode

Using a scantool, Clear DTC.

Operate the vehicle within DTC Detecting Condition in General Information.(Start and drive vehicle in gear and maintain vehicle speed is approx. 12 km/h or more(7 mph or more))

Are any DTCs present ?

▶ Go to the applicable troubleshooting procedure.

▶ System performing to specification at this time.