Supply voltage
1. Disconnect the connector from the automatic transmission position sensor.
2. Using a multimeter, set it to voltage measurement mode.
3. Connect the positive lead of the multimeter to the sensor’s power terminal (usually labeled “B”, “V” or “+”).
4. Connect the negative probe to ground (car body or negative battery terminal).
5. Turn on the ignition and check for voltage. It is usually around 12 V.
Resistance
1. Leave the sensor connector disconnected.
2. Set the multimeter to resistance (Ohms) mode.
3. Connect one multimeter probe to the “A” terminal of the sensor and the other to the “B” terminal.
4. Slowly move the gear shift lever through all positions.
5. The resistance should change as you switch to each position.
Waveform
1. Connect the connector back to the automatic transmission position sensor.
2. Connect an oscilloscope to terminals “A”, “B” and “C” of the sensor.
3. Start the engine and move the gear shift lever through all positions.
4. The oscilloscope screen should display a continuous waveform corresponding to the shift lever positions.
Pressure
In some car models, the automatic transmission position sensor also serves as a pressure sensor.
1. Connect a pressure gauge to the pressure port.
2. Start the engine and move the gear shift lever through all positions.
3. The pressure should change when switching to each position.
Fault codes
1. Connect the diagnostic scanner to the vehicle.
2. Read stored trouble codes.
3. Consult your vehicle’s repair manual to resolve any trouble codes associated with the automatic transmission position sensor.
Additional Tips
*If you do not have access to an oscilloscope, you can test the automatic transmission position sensor using an analog voltmeter. Set the voltmeter to AC current mode and connect it to terminals “A” and “B”. When changing gears, the voltage should change.
* If the automatic transmission position sensor is faulty, replace it with a new one. Do not attempt to repair the sensor as this may cause further damage to the transmission.