WHEEL SPEED SENSOR OUTPUT VOLTAGE MEASUREMENT


1.Lift up the vehicle and release the parking brake.
2.Disconnect the D-232 and D-233 ASTC-ECU connector, and measure at the harness-side connector.
Terminal No.
Front-left
 Front-right
 Rear-left
 Rear-right
30
 27
 46
 60
31
 28
 47
 61
3.Rotate the wheel to be measured by 1/2 to 1 turn, and use a multimeter (AC mV range) or an oscilloscope to check the output voltage at this time.
Output voltage:
  • 42 mV or higher when measured using a multimeter
  • 120 mVP-P or higher when measured using an oscilloscope
4.If the output voltage is lower than that given above, the cause may be the following, so check or replace the wheel speed sensor if necessary.

  • Excessive clearance between pole piece of wheel speed sensor and rotor
  • Malfunction of wheel speed sensor

WAVE PATTERN INSPECTION USING AN OSCILLOSCOPE

After checking the connection of the wheel speed sensor harness and the connector, take a reading of the output voltage wave patterns for each wheel speed sensor using an oscilloscope as follows.
Start the engine, move the transfer selector lever to the 4H position and the transmission selector lever to D range (A/T) or 1st gear (M/T), and then spin the wheel.
note
  • You can also take a reading of the wave pattern by actually driving the vehicle in this condition.
  • The output voltage will be lower when the wheel speed is lower, and will become higher as the wheel speed becomes higher.

WAVE PATTERN OBSERVATION POINTS
Symptom
 Cause
 Remedy
Wave pattern amplitude is too small or is non-existent.
 Malfunction of wheel speed sensor
 Replace the wheel speed sensor
Excessive variation in wave pattern amplitude (However, this is not a problem if the minimum amplitude is 120 mV or higher.)
 Excessive axle hub runout or offset
 Replace the hub
Malfunction of ASTC-ECU earth
 Repair
Noise appearing in wave pattern, or distorted wave pattern
 Open circuit in wheel speed sensor
 Replace the wheel speed sensor
Open circuit in harness
 Repair the harness
Incorrect wheel speed sensor installation
 Install the sensor correctly
Chipped or broken rotor teeth
 Replace the rotor
caution The wheel speed sensor cables move together with the movement of the front and rear suspension. Accordingly, you should shake the sensor harnesses while observing the wheel speed sensor output voltage wave patterns.