I had a knock sensor fail on My GS430 Sport. Changed the one relating to the fault code and problem was resolved. Does need the inlet manifold off, but wasn't too bad a job all in all. I ordered replacement inlet gaskets and throttle body gaskets, but I recon the old ones would've been fine.
Have you tried any other code readers, or just the one? Where are you located?
Sent from my iPhone using Lexus OC