So yesterday my GX suddenly started to make a chainsaw-buzz sound from what I think is in the under-center-middle of the dash. The 1st one yesterday just started while driving, about 4min after leaving the driveway. Now is happens after every start, but not immediately, sometime 10sec after start, sometimes 1min after start. It sounds for about 5-6sec then goes away, not to return until after the next start. I would say the freq of the sound is near 200-250Hz, and it's fairly loud. Does not seem to be AC related, happens with AC on or off. No CEL light or anything.

Anyone know what this is?

 

I don't have a GX but know on Tundra's the air induction pump was a common problem that sounded a bit like that

 

I fixed my secondary air pump when I did the injectors.

This sound comes after that air pump turns off. I may get the sound 4/5/8min after leaving the driveway, etc. Maybe it could be one of the valves to that air pump system, those valves sit at the very back of engine right up on the firewall.

 

Ok, I think I know what it is. The HVAC diverter mechanism. It was making birdy chirp sounds for past year or so, that sound stopped and this new one arrived. I need to replace that diverter control box.