For service and parts needs, visit your dealer. You will receive genuine GM parts and GM-trained and supported service people.
Genuine GM parts have one of these marks:

Vehicle Care
California Proposition
65 WarningTiming Chain Tensioner Replacement Valvetrain Valvetrain Timing Timing Belt Tensioner
Special ToolsEN-45027Tensioner ToolFor equivalent regional tools, refer toSpecial Tools.Removal ProcedureDisconnect the negative battery cable. Refer toBattery Negative Cable Disconnection and Connection.Remove the camshaft cover. Refer toCamshaft Cover Replacement.Remove the timing chain tensioner. ...