How to Determine the Condition of a Three-Wire Vehicle Speed Sensor?

1 Answers
OIris
07/30/25 2:47am
The three wires of a vehicle odometer sensor are the power wire, signal wire, and ground wire. By intermittently grounding the signal wire, if the odometer needle swings, it indicates that the odometer is functioning properly. Otherwise, it is damaged. Below are more methods for detecting the speed sensor: 1. Multimeter resistance check: Remove the speed sensor connector and use the multimeter's resistance setting to check the resistance between the two leads of the sensor. 2. Automotive oscilloscope test: Rotate the transmission's output shaft and use an automotive oscilloscope to detect the signal voltage waveform between the two leads of the speed sensor. A good sensor will show an AC waveform, with the amplitude and frequency increasing as the output shaft speed increases. 3. Function of the speed sensor: The speed sensor is used to detect the speed of electronically controlled vehicles. It also has other functions such as torque converter lock-up in automatic transmissions, automatic transmission shifting, engine cooling fan operation, and cruise control.
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