ABS <4WD> ± On-vehicle Service
35B-22
ON-VEHICLE SERVICE
WHEEL SPEED SENSOR OUTPUT VOLTAGE
CHECK
1. Lift up the vehicle and release the parking brake.
2. Disconnect the ABS-ECU connector and then connect
the special tool to the harness side connector. (Refer to
P. 35B-27.)
3. Rotate the wheel to be measured at approximately 1/2± 1
rotation per second, and check the output voltage using a
circuit tester or an oscilloscope.
Wheel speed
sensor
Front
left
Front
right
Rear left Rear
right
Terminal No. 15 17 2 4
14 18 1 5
Output voltage
When measuring with a circuit tester:
42 mV or more
When measuring with an oscilloscope:
120 mV p-p or more
4. The followings are suspected if the output voltage is lower
than the value described above. Check the wheel speed
sensor, and replace if necessary.
D Too large clearance between the pole piece of the
wheel speed sensor and ABS rotor
D Faulty wheel speed sensor
Inspecting Waveforms With An Oscilloscope
Use the following method to observe the output voltage
waveform from each wheel speed sensor with an oscilloscope.
D Start the engine, and rotate the rear wheels by engaging
1st gear (vehicles with manual transmission) or D range
(vehicles with automatic transmission). Turn the front
wheels manually so that they rotate at a constant speed.
NOTE
1. The waveform measurements can also be taken while
the vehicle is actually moving.
2. The output voltage will be small when the wheel speed
is low, and similarly it will be large when the wheel speed
is high.
Check connector
MB991547
ABS-ECU
Body side harness
When turning by hand
When idling (5± 6 km/h), 1st gear (M/T)
or D range (A/T)
10.0 ms/DIV 1
V/DIV
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