Illumination of the Check Engine Light can be caused by a loose or worn gas cap.Google+
Car Problem Reports
Pontiac Montana Check Engine Light Due to Gas Cap Issue
Pontiac Montana Problem
Average Mileage: 133,887 mi (79,000 mi - 280,000 mi)
Visitor, 2006 Pontiac Montana
Our light has been on for a while now. Changed the gas cap and is still on. What now?
Visitor, 2006 Pontiac Montana, 200,302 mi
light just will not go away no fix
Visitor, 2001 Pontiac Montana, 120,345 mi
Check engine light comes on due to loose gas cap
Visitor, 2005 Pontiac Montana
Check has cap light came on then check engine. Put on a new gas cap fine for two weeks then started again . Bought a new gas cap and again both check gas cap and engine light is on two weeks later.
Visitor, 2006 Pontiac Montana, 130,000 mi
sometimes after fueling or just by turning on the car the check engine light would come on and it would say check gas cap so every time i would fuel i would tighten the gas cap extra hard and i would push and tighten and i never saw the check gas cap message ever again.
Visitor, 2007 Pontiac Montana, 82,000 mi
just bought this two days ago, gas cap message came up yesterday, light came on today for check engine and the gas cap light is still on. going to try to replace the gas cap and see if it fixes it
Visitor, 2004 Pontiac Montana, 102,000 mi
not fixed..just tighten the cap well each time it is opened
Visitor, 2005 Pontiac Montana, 112,000 mi
I have had to replace my gascap several times over the last few years. It gets frustrating and expensive.