how nessary to replace at overhaul?

 

You did not give us any information about what vehicle you are working on.

Unless you found a problem with the Knock Sensor, or any of its wiring, it will be fine to reuse.

 

At least in the 3VZE, it is almost a given that you replace the "pigtail" from the knock sensor out under the lower intake manifold. Not very expensive, in a hellish environment, and a simple failure (leaky insulation around the shield? ) can keep the ECM from getting the signal.

But the knock sensor itself is almost bullet-proof. Still, it's hard to replace, so the $80 to replace it MIGHT let you sleep at night. Mine is original.

 

sorry it is a 1991 pickup with 3.0L v-6 ,auto trans,ARB lockers running Matt tracks mostly in deep snow.i pulled engine to re place main berings because of low oil pressure.tought this far might as well do the rest.has 50,000 hard miles.

 

Since you have the 3VZ-E, I would take Scope103's advice and inspect the knock sensor "pigtail" harness. These tend to fall apart over time and use in the harsh environment they live in. It may even be advisable to replace the harness out of preventive maintenance (I usually don't recommend replacing parts until they are proven bad, but at this point, the majority of the original harnesses are not in the best of health).

The knock sensor wiring is shielded and both the sensor wires and shield wires need to be intact for the ECU to correctly read the knock signal.

Was the check engine light on prior to the engine work?

 

no,no cel light on running strong just low to no oil pressure when hot.i am in prosses of replacing crank and bearings c ylinders look good but as long as this far going to through in pistons and rings.sugjestions on head gaskets?toyota or after market/? thanks for the advice. carl