Depending on the engine design, the timing drive can be either belt-driven or chain-driven.
.
List of services within the timing drive replacement procedure:
• Timing belt or chain replacement
• Timing drive tensioner and pulley replacement
• Guide rail replacement (for chain drives)
• Pulley and sprocket replacement
• Water pump replacement
• Oil seal and gasket replacement
• Setting the correct valve timing

When replacement is required:

• Scheduled mileage or service life limit has been reached
• Appearance of unusual noises during timing system operation
• Cracks, wear, or delamination of the belt are detected
• Valve timing errors have been diagnosed
• Poor engine starting
• Improper engine performance

Warning:

A routine and critical procedure on which engine operation directly depends.
Wear or breakage can lead to severe engine damage.