Apply power to the circuit.
Set the rotary dial of the DVOM to the V (AC) position.
Connect the positive lead of the DVOM to the circuit to be tested.
Connect the negative lead of the meter to a good ground.
Press the Hz button on the meter.
The DMM will display the frequency measured.
Measuring frequency is a very important part of diagnosing the ABS system, Vehicle Speed Sensor (VSS), knock sensors, etc.These systems use a frequency signal back to it's computer for input data and control parameters.
How To Measure Frequency