My 2005 Bonneville'* "Service Engine Soon" light came on a couple of weeks ago. The non-dealer garage "hooked to analizer, checked codes, replaced gas cap, cleared codes, reset" for $64.98 ($19.98 for cap; rest for half-hour labor). Light stayed out for 12 days and now is back on. Any ideas? Go back to garage and . . . ?

Go to a place like autozone and have the code read. Then post it here. Did they tell you what the code was? That'* a lot of money to put a new gas cap on. It take all of about 5 mins to read a code, if that. And 30 seconds to put a cap on.

No, the mechanic didn't mention code number. I'll try to get down to Autozone for code. He said he also did a "smoke test" (but it wasn't listed on receipt).

This sounds like a GXP problem that has been mentioned in another area of the forum.

Here'* one thread on the problem with some solutions https://www.gmforum.com/t280907/

Yeah bro you kinda got screwed in costs. Autozone would have checked and cleared code for free. Then all you woulda had to pay for was the gas cap if you even really needed a new one.

I called the garage and they say to bring it in and they will clear and reset the code this afternoon. I too question the need for a new gas cap, but if not the cap, wouldn't the problem be something worse and still recur until the underlying problem is fixed?

When I got my SSEi the Sevice light was on and the the info screen was telling me to check the gas cap. So i went got the code cleared and changed the gas cap. not a day later i was getting the same code alerts. So i took it to a real shop. Turns out i had a bad thermostat sensor which is why the engine light came on. I to this day have no idea why i kept getting the check gas cap alert but it eventually went off. and i started exclusively using Shell V-power fuel(propably unrelated) But im just letting you know what worked for me.

After calling the garage, they said to bring the car in this afternoon. The mechanic (different than the one that worked on it the first time) made note of the code (442), cleared the "Service Engine Soon" light and checked the gas cap that had been replaced, without doing anything further. He said to call again if the light comes on again for a more in-depth study.

442 EVAP system small leak detected

Check the vacuum lines, if it'* cracked you have a leak.

My mom'* car had this same code. The vacuum line between the Fuel Pressure Regulator and the Throttle Body had been cracked/open. Inspect all the vac lines under your hood.