4D56 Crankshaft Pulley.

4D56 Crankshaft Pulley
The crankshaft pulley is a mechanical device that is directly connected to the vehicle’s crankshaft. It typically uses one or more belts to drive other vehicle accessories, such as the power steering pump, A/C compressor, and alternator.

Also, there is usually a harmonic balancer integrated into or bolted to the crankshaft pulley. The primary purpose of the balancer is to absorb vibrations applied to the engine’s crankshaft.

A bad crankshaft pulley or harmonic balancer can cause symptoms like engine vibration, abnormal knocking noise, inoperative engine accessories, and engine failure.