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Greg A
Greg A, Master Troubleshooter
Category: Buick
Satisfied Customers: 8861
Experience:  Working with Electronics & Cars for 25+ Years
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2005 Buick LeSabre: with 82,000 miles..cap..alarm..service engine soon

Customer Question

I have a 2005 Buick LeSabre, with 82,000 miles and the "gas cap loose" alarm came on a couple of days ago. It did not appear loose, and now the "service engine soon" light is on. What is the problem?
Submitted: 8 years ago.
Category: Buick
Expert:  Greg A replied 8 years ago.

Hello & Welcome,


What the next step would be is to have the diagnostic test codes (DTCs) pulled from the car's computer. This is done by connecting a scan tool or code reader to the diagnostic connector (driver side, near the steering column). The good news is, many auto parts stores provide this service for free, in the hopes of selling you parts to fix the problem. But the goal here is to get the exact error codes, which are usually 1 letter followed by 4 numbers. If you can get the code(s) and then post them back here, we can get a good idea of what is happening and continue to diagnose this issue.


I hope this helps. Please let me know what you find.


Take Care, Greg A.

Customer: replied 8 years ago.
Dear Greg A...

   Unfortunately, the info you sent contains things I already knew...I have an appointment at the dealer already and they think that it is a vent valve. They told me this just by my describing what had happened. I was just hoping that they might be's about a $200 repair. I changed the gas cap thinking that it might be as simple as that, but this appears to be a no go. At least now the loose gas cap alarm only goes off once when I start the car, and stays off until I shut it off and start it again...but the check engine soon light stays on. Sorry that I can't accept this...thanx for your time.

Expert:  Greg A replied 8 years ago.

Hi again,


Not a problem. Without knowing the code for the particular issue, it is difficult to say what the exact problem is - even for the folks at the dealer.


I would still recommend that you have the code read - for free - just so that you know what it is and that the dealer is not just "taking a guess" as to what may be wrong.


Take Care, Greg A.