All automatic tensioning mechanisms for all serpentine drive belts are the same. They all have a strong spring, with anywhere from 90 to 180 foot pounds of torque, connected to a flange or arm that has a pulley mounted on it. They are mounted to the engine with either a single bolt or a stud and nut to secure it. The purpose of the tensioner is to take up serpentine drive belt slack as it stretches and to maintain the proper belt tension. Most tensioner spring housings have an indicator marks that show when the serpentine drive belt has stretched to the point that requires replacement.

Checking the tensioner pulley is the same as the idler pulleys, check for smooth operation with no binds or roughness. You also need to check the tensioner spring. Using the appropriate tool, move the tensioner slowly. If it feels rough or hear a clicking or any other noise, you should replace it. Automatic tensioner's go bad quite often. Bearings will go bad, the springs break, the housings crack, pulleys break or get damaged and mounting bolts get loose and break. So if you check nothing else, check the automatic tensioning mechanisms!