How to Test a Crankshaft Hall Sensor

The computer uses a crankshaft sensor to determine top dead center on the number 1 cylinder. This is used to fire the spark plugs and adjust the timing when the spark plugs fire. The crankshaft sensor is a hall-effect sensor, which uses a fixed magnet that senses a rotating pole piece that produces a magnetic fluctuation. The computer uses the fluctuation created as the pole piece passes in front of the magnet to trigger the ignition sequence.

Difficulty: Moderate

Instructions

Things You'll Need:

• Volt-Ohm meter
• Vehicle code scanner

1. Install the vehicle code scanner by inserting its cable end into the OBD port located under the driver's side dash.

2. Turn the ignition key to the "on" position without starting the engine.

3. Press the "Read" button on the scanner, and, within a few seconds, it will display a code. This code will be in the form of a letter followed by four numbers. Cross-reference these numbers with the code sheet that comes with the scanner, and the code will be identified with a description of the failure. If the scanner shows a code for the crankshaft sensor, the computer sensed a failure in the sensor.

4. Check the electrical connector for power with the key on, using the voltmeter. If there is battery voltage, test the black ground lead on the sensor with it attached. Test the ground wire from the sensor connector to ground. It should not have more than 100mv. If the reading is higher, the sensor is bad.

References

• Don Bowman, A.S.E. Certified Mechanic

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