1996 Mercury Villager,3.0 V6 engine. Where is the knock sensor located? Vehicle in question runs great. It has 239k miles. Probably needs a timing belt too. How long can I go before replacing the knock sensor?
Knock sensors don't always throw a CEL when they go bad. There can be electrical deterioration (No, I don't understand how or why, but it happens), or the sensor can go "deaf," in which you'll start hearing the engine pinging under some loads.
If visibly cracked and deteriorated, you should replace them - as this is one way they can "go deaf." If the vehicle has developed a pinging issue - replace.
The knock sensor on this engine is between the cylinder banks below the lower intake manifold. If it fails it will not set a DTC on this particular engine.
This picture shows the location with the heads and manifold removed.