ViPeRs103

I have a 2001 ES300 in which it has 120k on it. I've never had a knock sensor code yet to illuminate the MIL (Multifunction Indicator Lamp).. With that being said would it be necessary to replace the knock sensors along with the wiring harness for the sensors bypass hose intake manifold gaskets and the intake plenum gasket. I heard from many people including Lexus these engines are notorious for this to occur and also that the sensors themselves become soft giving a false reading as they slowly degrade!? What are some opinions from you folks!? Thank you again

ES300doc

No need to fix whats not broken. The biggest culprit here is the wiring harness connectors at the knock sensors get brittle from being baked in there for so long. Somewhere south off 200k miles you might be due for new head gaskets and at that time you can install a new harness if needed. We sold a 96ES300 to my brother in-law that has 312,000 miles and it's still has the original knock sensors and harness. My daughters 97 ES300 has 217,000 miles and it's running the original knock sensors and harness. I did install new head gaskets on both of these cars but found no issues with the knock sensors when I was in there.
Tip: If your in there doing gaskets or something and need to remove a knock sensor connector, heat it up with a heat gun or hand held lighter and they will normally unplug without damaging them.

Bumbobee

I just did my knock sensors. They went bad around 260,000 km. Well I shouldn't say "they", it was maybe 1 sensor, or the harness, not sure. In any case I replaced both and the harness. Also did the coolant bypass hose. Did not have time to replace the valve covers.

I also had to replace my variable valve timing solenoids and oxygen sensors not too long ago. Oh and my transmission went last year so 2 k for a rebuild.

Hopefully the car now lasts me another 250 k km.