I have a 2021 4Runner that developed an odd noise that sounded like it was coming from the driver's dash or firewall area. It only occurred over 15mph and drove me nuts. It got progressively more annoying over the last 10k miles. The noise only seemed to happen in colder/dryer weather and I ruled out the suspension and hood bump stops, as it wasn't consistent with suspension travel or bumps on the road.

I also noticed the same noise in a 2018 4Runner I recently rode in, which I thought was odd.

Tonight I poked around the front of the vehicle. Banged on the fenders to see if the mud flaps were loose, moved the suspension, etc. Turns out the noise is coming from the "screws" or clips that hold the rubber fender/engine liners to the inside of the fender "liner".

I took a toothpick and generously applied some silicone grease behind the rubber liner around the top two screws. Noise is now completely gone. I think the rubber liners may wear, contract, or dry out in cooler weather and allow the "screws" more freedom of movement, creating the noise.

Is there a TSB on this issue that I may have missed? It seems like Toyota would have put some gaskets in between the rubber liners and the body?