ERR6951LR - Timing Belt TensionerTiming Belt Tensioner for the 2. 5L Td5 5 Cylinder Turbo Diesel engine timing system. The tensioner pulley bears directly against the timing belt and maintains the correct running tension between the crankshaft drive sprocket and the camshaft sprocket. A correctly tensioned belt is essential for cam timing accuracy; a worn or seized tensioner allows belt slack, increasing the risk of belt jump and valve to piston contact. Replace as a matter of course