WARNING: This page is about a different car, the 2006 Buick LaCrosse and 2006 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: View Of Coolant Heater - LY7, KO5
Courtesy of GENERAL MOTORS CORP.
Install the coolant heater.
Connect the coolant heater cord to the coolant heater.