First take it out and clean it, you will see a 10mm bolt holding it in the top of the block behind the cylinder head. Undo the bolt and gently pry the sensor out with a screwdriver, try not to pull on the wire to much. With the sensor out, try and start the car. It shouldnt fire at all as this sensor tells the ecu about engine rpm and related ignition timing. Now clean any grease from it, put the sensor back in its hole and try to start the engine, if it now fires (or even better runs ok) the sensor is working. Hope this helps.

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