Mitsubishi MOTORS Space Runner 1999 Workshop Manual Supplement page 806

When turning by hand
When idling (5 – 6 km/h),
1st gear (manual trans-
mission) or D range (au-
tomatic transmission)
10.0 ms/DIV 1
V/DIV
Points In Waveform Measurement
Symptom
Too small or zero waveform ampli-
tude
Waveform amplitude fluctuates ex-
cessively (this is no problem if the
minimum amplitude is 100 mV or
more)
Noisy or disturbed waveform
NOTE
The wheel speed sensor cable moves following motion of the front or rear suspension. Therefore, it is
likely that it has an open circuit only when driving on rough roads and it functions normally on ordinary
roads. It is, therefore, recommended to observe sensor output voltage waveform also under special conditions,
such as rough road driving.
ABS <2WD> –
On-vehicle Service
Inspecting Waveforms With An Oscilloscope
Use the following method to observe the output voltage
waveform from each wheel sensor with an oscilloscope.
Start the engine, and rotate the front wheels by engaging
1st gear (vehicles with manual transmission) or D range
(vehicles with automatic transmission). Turn the rear
wheels manually so that they rotate at a constant speed.
NOTE
1. Check the connection of the sensor harness and connector
before using the oscilloscope.
2. The waveform measurements can also be taken while
the vehicle is actually moving.
3. The output voltage will be small when the wheel speed
is low, and similarly it will be large when the wheel speed
is high.
Probable causes
Faulty wheel speed sensor
Axle hub eccentric or with large runout
Open circuit in sensor
Open circuit in harness
Incorrectly mounted wheel speed sensor
ABS rotor with missing or damaged teeth
35B-17
Remedy
Replace sensor
Replace hub
Replace sensor
Correct harness
Mount correctly
Replace ABS rotor