Illumination of the Check Engine Light can be caused by a loose or worn gas cap.Google+
Car Problem Reports
Buick Rendezvous Check Engine Light Due to Gas Cap Issue
Buick Rendezvous Problem
Average Mileage: 106,794 mi (51,000 mi - 288,369 mi)
Visitor, 2007 Buick Rendezvous, 90,000 mi
Check engine light seems to be related to the gas cap. I clean the gasket on the gas cap and assured tightness and problem went away. Comes back when the wife refills the gas.
Visitor, 2006 Buick Rendezvous, 130,000 mi
I also have light for gas cap leak.
I had the service engine soon diagnosed by Autozone and they said to replace the gas cap and add fuel injector cleaner. So far it worked.
Visitor, 2005 Buick Rendezvous, 96,000 mi
Replaced gas cap and always over tighten. Seems to work most of the time
Visitor, 2007 Buick Rendezvous, 70,000 mi
I've replace the gas cap, and have issues filling the tank without the pump stopping consistently. Nothings worked yet.
Visitor, 2006 Buick Rendezvous, 110,000 mi
We had this problem with gas cap starting at about 80.000 miles.
Visitor, 2006 Buick Rendezvous, 121,000 mi
SES light came on. Abbout 50 miles later, gas cap light came on tightened cap both went off 100 miles later, same thing, but tightening cap doesn't help.
Visitor, 2002 Buick Rendezvous
I've replaced the gas cap at least 3 times in 78000 miles.
Never again a GM car!
Brake light stays on and warning bell continues to chime. Brake is off and car drives normally.
Visitor, 2003 Buick Rendezvous, 79,000 mi
Check engine light was on for about a year. I had Auto Zone run their diagnostic and bought a new gas cap and had the O2 sensor replaced. This was good until the next time I filled up the gas tank. The check engine light came right back on.