Question 2005 4Runner Code Alarms?

[JTUNDRA4X4]

My wife has an 05 4Runner that has Code Alarms on. I took it to the dealer to do regular service and asked if they would reset it. They said sure... $100.00. Yea right, I laughed that one off. Done free at the new place of business to get an oil change.

Anyways, My question: Will a faulty gas cap make these codes go off? The code was reset and the gas cap is bad. We tighened it up as best we could and it stayed off a couple days, but then came back on.

Thanks.

John

[JTUNDRA4X4]

Also, where is the best place to buy a cap? Dealer?