Hi All,
Just ran across this thread, and like to add some info and hope someone might solve this mystery (at least I thought is was normal as stated below).
My is a 2000 RX300 AWD (brand new of the lot) and have the similar issue since day one.
The issue: As soon as I insert the key into the ignition switch (without turn key), the buzzing sound somewhere in the engine compartment begin. Once I pull out the key, the sound stop immediately. this sound happens every single time the key is insert.
Lexus response: Normal (in Short), also try on 2 other car on the lot and found out they have same problem "normal"
Observation: Once the buzzing sound begin after key is insert, it seem to never stop since I have waited well over 2 minutes (maybe wait longer next time). However, when I turn the key to the position (before the start) and turn it back to the position (where key just insert), the sound is no longer exist. At this point I let the key sit there for 15 minutes and still buzzing sound.
Test: As soon as I remove the key then insert the key again, the buzzing sound happens again, I then went to the cycle of -remove then insert- for 15 times in a roll, the buzzing sound happens every single time, but when I turn the key up then turn it back to the insert position (mentioned in Observation), the sound immediately stop. Now start engine and drive around the block then turn key to all the way to off position then wait for 5 minutes, did not notice any sound at all.
Now what: Until this very day, I still have the same issue and still cannot determine what is the cause of where exactly the sound come from under the hood. Regards to Lexus, in short, take a look and then still come back with the word normal without explaining what is it…
Solution: None. However, I am still currently searching for all of the wiring diagrams that cover from the moment the key is insert into the ignition switch and hope that I can find out something by tracing what happen when the key is insert. But for now, I have to stuck with it.