Emission control light, WTH

[albuquerqueith]

Problem started the last six months I owned my old Sonic (2012 1.8L 5M). Took to dealer several times. Told it was caused by "bad" gas, cracked air intake hose, etc. Don't think they ever really nailed down the real cause or fixed it.

Now 5k miles on my new Sonic (2015 1.4L 6M) and the light is on. Any idea what is the real cause?

 

[oldslowchevy]

What codes are coming off the ecm when it is scanned?

 

[albuquerqueith]

Just got back from dealer. Blamed it on an ill fitting (factory) gas cap. Sounds fishy. We'll see.

 

[Natesriv]

believe it or not, that's a real thing. If there's a "leak" your evaporative emission controls will fault and trigger a light.

Quick and easy fix!

 

[albuquerqueith]

believe it or not, that's a real thing. If there's a "leak" your evaporative emission controls will fault and trigger a light.

Quick and easy fix!

But if that was the issue, wouldn't it have started Day 1? The cap didn't go bad in six months.

 

[hammrdwn510]

Could have
Drastic temp changes?

 

[albuquerqueith]

Light went on again and they replaced the cap again? WTH? A cap should last the life of the car+, surely this isn't the cause. Any ideas?

 

[ohio_grad_06]

Begin buying caps from auto parts store, might be cheaper?

 

[albuquerqueith]

Begin buying caps from auto parts store, might be cheaper?

Only 19k miles, under warranty.

 

[Hawkdsl]

Leak in a hose somewhere. Evap system has it's own plumbing.

 

[spacedout]

Light went on again and they replaced the cap again?

Sounds like you have an incompetent dealer, they should have tested the EVAP system for leaks since the cap didn't fix the issue the first time. Honestly I would not take my car there again and waste my time, would try to find a better service department at a different dealer.

Not sure why GM lets so many bad dealers proudly display the Chevy name on the front of the building, it reflects badly on the brand as a whole.

 

[Thesd45]

My sister had a similar issue on her old Grand Am. After replacing the gas cap the mechanic discovered that the filler tube from the gas cap to the tank was cracked. If the cracked opened up the system lost pressure and the check engine light came on, but sometimes it somehow stayed closed and the system maintained pressure...