Component Tests and General Diagnostics

ABS SENSOR OUTPUT VOLTAGE MEASUREMENT
Lift up the vehicle and release the parking brake.





1. Move the lock lever of the ABS-ECU connector as shown, and then disconnect the ABS-ECU connector.





2. Push up and unlock the hooks of the ABS-ECU connector as shown in the illustration, then remove the connector cover.





3. Manually turn the wheel to be measured 1/2 to 1 turn/second. Measure the output voltage with a voltmeter or oscilloscope.





NOTE: The output waveform is low when me wheel speed is low. Similarly, it will be higher as the wheel speed increases. Waveform may also be observed by driving the vehicle.

Output voltage:
^ Minimal voltmeter reading: 42 mV
^ Maximum voltmeter reading: 300 mV
^ Minimal oscilloscope reading: 120 mV
^ Maximum oscilloscope reading: 600 mV

Probable causes of low output voltage
^ ABS sensor pole piece-to-ABS rotor clearance too large
^ Faulty ABS sensor

NOTE: Check the connection of the ABS sensor harness and connector before using the oscilloscope.





4. To observe the waveform with an oscilloscope:
^ Front Wheels: Shift into low gear and drive the wheels.
^ Rear Wheels: Turn the wheels manually at a constant speed.

POINTS IN WAVEFORM MEASUREMENT





NOTE: The ABS sensor cable moves in relation to motion of the front or rear suspension. Therefore, it is likely that it has an open circuit only when driving on rough roads but it functions normally when driving on smooth roads. It is recommended to observe sensor output voltage waveform also under special conditions, such as driving on a rough road.