Does a mechanic need to reset the "Check Engine" light on a 2004 Buick LeSabre first, to see if replacement of a GAS CAP fixes a "Loose Gas Cap" error message?


Asked by Feb 23, 2016 at 11:28 AM about the 2004 Buick LeSabre

Question type: Maintenance & Repair

I had a "Loose Gas Cap" message on my 2004 Buick LeSabre that caused
the "CHECK ENGINE" light to come on.  I replaced the gas cap and have
driven the car for over a 100 miles in all types of traffic.  I was told by
AUTOZONE that this is necessary for the emissions control system to see
that there is no longer a vapor leak, and if the problem has gone away, it
should extinguish the "CHECK ENGINE: light.

The light has not gone out yet.

Is it possible that a mechanic needs to RESET the Check Engine light
FIRST?   For all I know  I will then need to drive another 100 miles and see
if the light comes back on, to see if the new gas cap fixed the problem?  If I
do this, how many miles would the car need to be driven to be certain the
problem is fixed?  Incidentally AUTOZONE said they are not allowed to
reset Engine Lights; only mechanics can do that.

4 Answers


Yes all the above is correct. It should have reset itself by now. Might be something else in the system causing the gas cap light to come on. What it's sincing is some sort of vapor leak in gas tank system. Could be bad cap or vac hose/canister issue. Smoke test done by a mechanic is about the only way I know of to check for other gas system emission leaks.

1 out of 1 people think this is helpful.

Mine has same error code for 100,000 miles roughly. Gas cap/ pump/ vacuum lines/ etc have been replaced. Unhook the battery for 15 min. Both terminals and then the light should be off.. Unless the problem isn't fixed


DANGER DANGER Unhooking the battery can trigger the THEFTLOCK on stock radio. You have to have BUICK fix it for big bucks. The radio came with a CODE STICKER on it that has to be punched back in to unlock. No problem with aftermarket radios. Most times its the gas cap or o'ring on gas cap. Take so many start/stops to manually reset or just have Advance or Autozone reset.


Once the radio is programmed to a specific vin # it won't ever need programmed again. I have had my battery out many time and never had any trouble but I have went through all the codes for vapor lock and many more. Had mine 12 years plus and has 269,000 miles on the odometer.

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