Just got a new (used) truck. Dealer says the check engine light stays on because of a after-market locking gas cap. He resets it and away I go. Twenty minutes later, it comes on again and I ignore it for a week. I go in to have some keys made ($150 for two keys, chip needed for anti-theft program). I also replaced the locking cap ($20) with a factory cap. Light goes off for a couple of days and then it appears again. Dealer wants to charge $85 to do a diagnostic test.

I have had friends who have their light on for years without any problem. Is this just a gimmick to get you to bring your rig in and get it checked out all the time? What is the worst thing that can happen by ignoring it?

It seems to me that some times we try to idiot proof things to the point that it makes things worse.

Any suggestions for this situation?