My buddy's 02 SC430 from this thread has developed the same symptoms again only a month after the dealer "switched" the OCV:

https://www.clublexus.com/forums/sc-...ng-lights.html

They are now saying that it might be a defective part but are thinking its more likely sludge, and it would take a few hours to tear it apart to see what's up. And, if it IS sludge, they are telling him he may need to replace the engine???

This seems odd as my friend has always done regular oil+filter changes with synthetic, and even stranger that the dealer didn't say anything about sludge a month ago when they went in and determined the OCV valve had to be replaced.