How to tighten serpentine belt toyota yaris?

Before tightening the serpentine belt on your Toyota Yaris, you'll want to check the manufacturer's specification for what precisely this needs to be. Without more information (such as model year, engine, and trim level), I can't tell you what this is -- it varies across different variants. However, once you determine where it should be, the process for doing so is relatively simple. The downside is that it requires a specific belt tensioner tool, the Denso BTG20 Belt Tension Gauge. While workarounds exist, it's best to ensure that you're at the proper specification. From there, you'll need to adjust the serpentine belt tensioner pulley to lock in your new tension, and this should hopefully eliminate any drive belt squealing that you may have had.