CEL and it was the gas cap



I got a CEL(for about a week) on my 2005 Subaru Legacy that still was under powertrain and emissions warranty so I went to dealer. They had me sign for a $44 diagnostic fee. They read the code and it stupidly it was the gas cap loose at some point. (my wife loves full serve)

My question is if I had waited a few weeks would the light eventually go out since error condition had stopped or once on does CEL stick.

Thanksfully I got them to wave the diagnostic fee in paying for an overpriced rear brake job($300).


I hate to tell you this now, but you likely could have had that CEL read by a local auto parts store for free. Many of them will do that for you.

It is not unusual for a loose gas cap to cause a CEL, but it is also possible that it is something else. Even the same code could be a loose or defective gas cap or another problem with the vapor recovery system. We generally recommend checking for a loose gas cap first and often suggest replacing one next.

Your guess is right that in this case the light should have gone out after the cap was tightened and after the car was driven a few times without the loose gas cap.

The problem with assuming it is a loose gas cap, is that it could well be something else and that something else could be more serious or even a safety issue. It is best not to ignore a CEL in hopes that it will go away. HINT: Never ignore a blinking CEL. If it is blinking it is time to stop the car right where you are to avoid additional very expensive damage, even if it means pulling off the side of the freeway, don’t wait for an exit.

I would suggest avoiding trips to the dealer. Find a good local INDEPENDENT mechanic. In the long run it likely will save you a lot a aggravation and money. Even when under warranty there is seldom a need to visit the dealer. In this case you could have had the code read by the auto parts store for free and it would have cost you nothing.


“would the light eventually go out …”

Yes. A lit CEL will eventually go off once the error is condition is cleared. Depending on the code, the light may shut off immediately or it may linger for X number of drive cycles. A drive cycle is defined by the manufacturer; typically the car must travel at least A miles reaching B mph and then shut down. If the error condition is clear, then after maybe three drive cycles the light shuts off. This can easily occur in the course of a single day.


What threw me off was my cruise control light was flashing and disabled with a CEL on which I thought meant something more severe. This has been doing it for over a week and annoying my wife having no cruise.

My only reason for visiting dealer are Subaru Rewards(3% kickback up on credit card purchases up to $500/year). The $500/year does not go far as jobs are really high there though, sometime 50% higher than other shops I find.


How much money has that Check Engine Light and loose gas caps cost the American driver?


I don’t blame the CEL or the gas caps. I blame the federal regulatory beaurocracy with the runaway idle.

Every federal regulatory agency I can think of has bloated well beyond its original intent, fed on its need to continually justify its own existance.


Having your own code reader is a good thing to own I believe. For about the price of the diagnostic fee you can purchase one. If you are the handy type you may want to pick one up. Make sure you get one that will handle the protocol that Subaru uses for your model year if you do get one.


If you are still under warranty, you need to go to the dealer. I’m not clear why they wanted to charge you for the diagnostics since a CEL light will obviously affect emmissions which is a warranty item.


OBD-II polls all the sensors. If it sees that the sensor checking the gas tank is OK, it should reset on its own after a few restarts.


Eh? A little sunstroke, there, MB? A loose gas gap lets gasoline vapors out into the air, where (as unburned hydrocarbons) they contribute to smog and other pollution. The CEL coming on is a dope slap to the driver: “hey stupid, tighten the cap so the evaporative control system can do its job!” Carmakers are required to get their cars to a certain level of cleanliness, so they are entitled to turn the CEL on if the gas cap (which is part of anti-pollution gear) isn’t tight.