What is a common method to test an ABS wheel speed signal using a digital multimeter?

To effectively test an ABS (Anti-lock Braking System) wheel speed signal using a digital multimeter, measuring AC voltage is the common method employed. The wheel speed sensor generates a signal that varies with the speed of the wheel, and this signal is typically an alternating current (AC) voltage.

When the vehicle is in motion, the magnetic field around the wheel speed sensor generates an AC voltage corresponding to the rotational speed of the wheel. This is significant because the ABS control module interprets this AC signal to determine wheel speed and detect potential wheel lockup scenarios.

Using a multimeter set to measure AC voltage allows you to observe the variations in voltage as the wheel spins, indicating the sensor’s functionality and whether it is producing the correct signals. If the multimeter is set to measure DC voltage or resistance instead, it would not provide the necessary information about the sensor's performance since those settings do not capture the rapid changes in voltage generated as the wheel spins. Thus, measuring AC voltage is the most appropriate and effective method for diagnosing the correct operation of an ABS wheel speed sensor.