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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 there is no wheel speed signals within 10 ms to 20 ms at a vehicle speed ＞ 43.2 km/h or a deviation between sensors exceed the threshold or one or two wheels are at 2.75 km/h while the vehicle speed is at 12 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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Continuous (only no under voltage is not detected)

Enable Conditions

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If one (or two) wheel are at 2.75 km/h and the other wheels are above 12 km/h for longer than 1s.

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During driving, when the vehicle accelerates 18 km/h after a particular wheel speed gets to 2.75 km/h and stays there. At that time, If one (or two) wheel are at 2.75 km/h.

- This monitoring is performed at the following condition.

At the time the vehicle is accelerated to 12 km/h

Once after energizing the system.

If the vehicle was stationary for approx. 2 s.

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If one (or two) wheels are under 5 km/h and the two fastest wheels have a velocity above 12 km/h for more than 20 s.

Case2

Monitoring Period

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Continuous ( If vehicle speed ＞ 12 m/s)

- but this monitoring is disabled in the following event

aquaplaning.

interference.

supply voltage below 7.1 or above 18 Volts

Enable Conditions

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No wheel speed signals within 10 ms to 20 ms at a vehicle speed ＞ 12 m/s (43.2 km/h ).

- If the dynamic sensor monitor responses, the failures will be stored into failure memory immediately after a waiting period of 60 ms.

- If occurs low voltage active sensors during the waiting period of 60 ms no failure is stored in the EEPROM.

Case3

Monitoring Period

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Main Monitoring

The main monitor needs additional information of the ESP-sensors and is active for a velocity ＞ 20 km/h and no under voltage is detected.

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Backup Monitoring

- Continuous

Enable Conditions

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Main Monitoring

If the maximum difference of wheel speeds related to maximum wheel speed exceeds 5 %.

detection filter time :

- the above conditions apply for 20 s for 1 defective wheel speed sensor.

- the above conditions apply for 40 s for 2 defective wheel speed sensor.

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Backup Monitoring

If the deviation between the fastest and the slowest wheel is below 6 % related to the fastest wheel when the velocity is higher than 50 km/h.

When the velocity is below 50 km/h, if the deviation is an absolute value of 3 km/h.

detection filter time : normally 20 s

- In case of a detected curve, the threshold is increased with an additional value of 4 km/h.

Case4

Monitoring Period

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Continuous

Enable Conditions

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The pulse width of wheel speed sensor is below 2 ms when vehicle speed is ＞ 0km/h and ＜ 20 km/h.

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.

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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. 50 km/h or more(31 mph or more)

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

Specification : Approx. 50 km/h or more (31 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. 50 km/h or more(31 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. 50 km/h or more(31 mph or more))

Are any DTCs present ?

▶ Go to the applicable troubleshooting procedure.

▶ System performing to specification at this time.