2004 civic check engine light

[kender]

I always use shell gas in my Civic. About a week ago I got some generic gas. Yesterday ( with 1/2 tank used) , my check engine light came on. First time ever, with 42,000 miles on the car. I took it to Advance auto. They ran the codes, and said the downstream O2 sensor was bad ( $247 !!!). I said I would check prices. Then today the light went out. Could it have been the gas ( which is still in the car ), or is the O2 sensor going bad?

 

[Seguino]

I wouldn't worry if the light went out. A momentary glitch can cause a code, and it takes a few start cycles of the engine to make the check light go out. If the light comes on after fueling, the first thing to do is remove and retighten the gas cap. It could be as simple as a piece of debris causing a bad seal.

 

[bepperb]

Was it a P420 code? Those are bad gas (and all sorts of other things) misdiagnosed as a bad downstream O2 sensor all the time.

 

[JHZR2]

An 04 Honda with 42k should not have a cEl under any circumstances, that is just poor quality if the case. That said, glitches can occur, and poor quality fuel certainly can do funny things. If it goes away and doesn't come back, it is likely an anomaly. The peace of mind you can have is that the downstream sensor is post-cat and likely not necessary for ecu engine control... It is to verify catalyst efficiency. Since your cel is explicitly sensor, i'd guess it is a heater circuit that didn't work fast enough.

 

[kender]

Thanks for the reply's.
Seguino, I've had to tighten the gas cap on my wife's car a few times to get rid of the check engine light. So I checked mine right away and it was tight. Worth a try though.
bepperb, I don't know the exact code. Only what the auto parts guy said it was.
JHZR2, yeah, the auto parts guy said that the sensor should last a lot longer than 42,000 miles. I do lots of very short trips though. And didn't know if that could efect the O2 sensor's life.
Anyway, maybe it was a glitch.Time will tell.