ABS <4WD> ± On-vehicle Service
35B-23
Points In Waveform Measurement
Symptom Probable causes Remedy
Too small or zero waveform
amplitude
Faulty wheel speed sensor Replace sensor
Waveform amplitude fluctuates
excessively (this is no problem if
Axle hub eccentric or with large runout Replace hub
the minimum amplitude is 100 mV
or more)
Faulty ABS-ECU earth Repair
Noisy or disturbed waveform
Open circuit in sensor Replace sensor
Open circuit in harness Correct harness
Incorrectly mounted wheel speed sensor Mount correctly
ABS rotor with missing or damaged teeth Replace ABS rotor
Caution
Because the wheel speed sensor cables move together with the front and rear suspension, they vibrate
greatly when driving over poor road surfaces. As a result, the sensor harnesses should also be shaken
when monitoring of output waveforms of the wheel speed sensors in order to simulate conditions such
as driving over poor road surfaces.
ABS WARNING LAMP RELAY CONTINUITY
CHECK
Battery voltage Terminal No.
1 2 3 5
Power is not
supplied
Power is supplied
Hydraulic unit
and ABS-ECU
<L.H. drive vehicles>
<R.H. drive vehicles>
Hydraulic unit
and ABS-ECU
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