ABS OPERATION CHECK WHEEL SPEED SENSOR OUTPUT VOLTAGE CHECK 1.Lift up the vehicle and release the parking brake. 2.Disconnect the ABS-ECU harness connector and measure from the harness side connector. CAUTION: Use a special tool (inspection harness for connector pin contact pressure) to measure the output voltage at the harness side connector to prevent damaging the connector terminals. 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. 6 4 8 1 7 5 9 3 Output voltage When measuring with a circuit tester: 50 mV or more When measuring with an oscilloscope: 20 mV p-p or more 4.If the output voltage is lower than the above values, the reason could be as follows: •Faulty wheel speed sensor. So replace the wheel speed sensor.

Inspecting Wave Forms With An Oscilloscope Use the following method to observe the output voltage wave form from each wheel sensor with an oscilloscope •Start the engine, and rotate the front wheels by engaging D range. Turn the rear wheels manually so that they rotate at a constant speed. NOTE: Check the connection of the sensor harness and connector before using the oscilloscope. NOTE: The wave form measurements can also be taken while the vehicle is actually moving. NOTE: The output voltage will be low when the wheel speed is low, and similarly it will be higher as the wheel speed increases.

Points In Waveform Measurement