Engine Warning light on, oxygen sensor

[Blueridge9]

My 2004, automatic, 1.8L with almost 95,000 miles had the engine warning light come on Friday. Mechanic read it as oxygen sensor code PO331 I think, and reset it. Warning light has not come back on during light weekend driving. I had noticed the engine idling a little high a few times and the other day after turning it off in the driveway I smelled an odd sulfur smell.

I understand there are two sensors and they ordered the outward bound one to be replaced Monday. After reading here I also checked to be sure the PCV valve was good and that the gas cap was screwed on tightly and they are fine. Sounds like sometimes the oxygen sensor replacement did not remove the warning light. I hope I'm not doing an unnecessary replacement. Any other advice?

[Chiadog]

Barring any other symptoms of a bad O2 sensor such as decreasing gas mileage or erratic engine operation, I would reset the engine code and see if it comes back before I replaced the sensor.
Had a stray EGR code on my Saturn 2 years ago. Reset it and it came back a year later, at which time I cleaned the EGR valve. My Saturn had no symptoms of any engine problem before or after this!
good luck,
chiadog

[Salsa Guy]

According to my search it's a knock sensors #2. Strange thing I don't think these cars have 2 knock sensors.

[Blueridge9]

Thanks Chiadog and Salsaguy! So far the code has not yet returned. I wonder how much replacing an oxygen sensor normally costs?

[Chiadog]

A "Good" mechanic should have an advanced computer analyzer which he knows how to use. He could watch the output from the sensor in real-time and have an idea if the sensor is bad or not. It is probably a good time for you to ask all your family/friends for help finding a GOOD mechanic.
Second option and usually my choice is to do the job myself. Buy a cheap($80) scanner and a decent repair manual and go-for-it. At least you'll get an inexpensive education!
I have not replaced an O2 sensor on a Vibe, but it is generally a relatively easy job. From my perspective replacing easily accessible parts myself makes sense since the price of the part is often less than 1/2 the price a mechanic would charge for the job. Even if you replace an old part that was working properly, you now have a new part in place and you can look at other causes for the problem.
chiadog

[Salsa Guy]

The chances that it is an O2 sensor is unlikely. The code you posted I don't think applies to these cars. There codes that will point to a bad O2 but most of the codes involving the O2 sensor mean there is something else wrong. Swapping parts will more than likely not fix the issue and cost $$$ and time.