Your serpentine belt may be squeaking due to it being worn out. It could also be squeaking due to a faulty serpentine belt tensioner. The tensioner has internal bearing and over time those bearings will wear out and cause your tensioner to start making noise. Your tensioner should be replaced when the bearings are worn to keep you on the road. If the bearing breaks then it will cause your alternator to stop charging and then after it has drained your battery your vehicle will stop running.
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