Illumination of the Check Engine Light can be caused by a loose or worn gas cap.
2006 Buick Rendezvous Problem Reports
RepairPal Verified 2006 Buick Rendezvous Problem Reports
The AC may stop working due to a refrigerant leak from the condenser. GM has developed and updated condenser and mounting bracket to help prevent the replacement condenser from failing in the same manner.
The high pressure power steering hose will commonly leak fluid and should be replaced if this is the case.
The front struts may show signs of wear, or be excessively bouncy ride at freeway speeds. This may begin to occur at around 75,000 miles.