Hello Everyone ...
Yesterday the message "Gas Cap Loose Check Cap" showed .
The ESL - Engine Service Light in OFF .

I tried to close again the cap but it still show
What could be the problem ?
If I solve the problem The message will turn off automaticly or I need to RESET ?

Thanks !

I would assume once the car detects correct pressurization, it should turn off.
Most of the time the rubber sealing washer on the cap is the culprit.
I would recommend a new GM gas cap & stay away from after market ones.
You could disconnect both battery cables for a few minutes, that should clear that light/code.

I had this error a year or so ago, and replacing the gas cap did not solve the problem (although that'* probably the first thing you should try). I ended up finding a broken vacuum hose in the engine compartment. Here'* my thread:

https://www.gmforum.com/buick-172/ga...-spout-306988/

I think the car displays the "gas cap" error anytime a vacuum leak in the fuel system is detected, even though a leaky cap may not always be the cause.

Thanks Alot !!!!
I found broken pipe in the same location like you !
how you fixed it ?
you can send me the number of the part ?

Thanks !

The loose gas cap code, usually means a very small leak...if the cap was loose,and you tighten it, the light will not go off right away, until the diagnostic has run two consecutive times and has passed both times....

Sometimes, even putting a new cap does not work, due to rust/corrosion on the fill pipe where the seal of the cap mates......If I notice any corrosion, I use crocus cloth to clean the fill pipe before putting on the cap.....

You can go to any auto parts store and they can clear the code right away, to know for sure....

If clearing the code and a new cap does not take care of the problem, unless you see something "visual", like a broken vac line, you are just guessing....a smoke test will easily find the leak....

On "H" cars the usual culprits are the purge solenoid(bad solenoid, wiring to it eaten by rodents, bad vac lines to and from it), the vent solenoid(does not seal), or the gas cap.....

Check out the whole thread I linked... I ended up buying some rubber tubing and "making" my own replacement (for about $4), but the part # is in there for the new replacement part too (about $20). Or you can check into a junkyard replacement from a similar Buick model ($1 maybe) but then you run the risk of that one being just as old and prone to breakage.

If I fix the pipe i need to reset the computer ? or it'* go away by itself ?

It probably depends on exactly which codes have been alerted, but mine went away almost immediately once the vacuum leak was plugged. Sometimes it takes a few engine restarts and/or some driving to eventually clear the code, or you can always use a code reader or disconnect the battery for a few minutes to manually clear it.

The problem solved .
I fix the pipe and connected it again . the massage "Gas Cap Loose..." gone .

Thanks Scottydl

Glad it worked for you!!