Hi got some weird rattling sounds coming from the auxiliary belt under acceleration and my idle is super quiet suddenly no clue what the cause is and I have had no error codes come through, what could be the cause?
also when starting the car there has been clicking noise’s coming from the belt as well

https://youtube.com/shorts/733zy5eLYGQ?feature=share

 

Inspect the belt tensioner hydraulic rod (looks like a small black hatch lift). Over time, the plastic bushings on either end dry out, then crack and fall out allowing the circular metal ends of the rod to vibrate against the bolts holding it to the tensioner. It's an easy replacement (two bolts) through the passenger side wheel well once you remove the fender liner. $25 fix.

 

This bad boy. Mine went at about 48K in daily SoCal use. Rubber gets eaten alive there. Sounded like BB's rattling around in a coffee can.
https://www.rockauto.com/en/catalog/...r+damper,11663
https://www.outmotoring.com/belt-ten...8620210-d.html
Can change it out from above with a small combo wrench (8mm?)& patience. If you have giant orc size ham hock hands, probably won't be able to pull this off; pull the wheel and liner.

If you're a rubber hater you can rebuild it with polyurethane bushings for twice the cost but possibly more longevity:
https://www.pelicanparts.com/More_In...1221-010-M1333

Then 'while you're in there' consider changing out the belt - especially if you don't know how old it is - and give the tensioner, idler, alternator, AC compressor and blower pulleys a quick shake and spin to make sure they're not going. You'll need the "Tool®" if you don't already have one:

https://www.pelicanparts.com/More_In...L-026518SCH01A

[available from most vendors and Bezosworld, though some of the latter's appear to be sketchy quality]