Oxygen Sensor(S)

[shox]

Recently ive noticed my car gas mileage has dropped. Like 150-200 kms a tank....
Which normally is 500 ish. My engine light came on for 2 days, during that time i was working 12 hr days so i just drove to work and back and was planning to take it in. However it went out, and now that it is out my local mechanic cannot tell what is wrong. without the light on.

Ill probably have to take it to a dealership and pay big to get it put on there computers, which i dont want to do :/.

Has anyone ever had this issue? Ive even heard that these sensors should be changed every 5 years... as maint...

Any help would be appreicated.


99 alero 3400

thx

[StealthAlero]

Well oxygen sensors can range in price from $25 like my 2-wire unheated bosch was that i will be hooking my a/f gauge up too then they can go all the way up to like $300 for the super nice heated ones. An alero OEM should be around $75 bucks tops. So if you want to replace it first before dishing out way more cash at the dealership, thats what you'd be looking at price wise. Sorry i don't know what the problem is though.

[Fast Eddie]

The upstream O2 sensor cost me $39 for the heated one, from GM. I know I have this problem all the time (long story) and usually the trac off light comes on first.

Could be crappy gas, the PCM got a weird signal, any number of things. I will tell you that if you take it to autozone or where ever and they cannot find a code in it neither will you dealer. OBD-II standards ensure the duration the code kept is standard so the the $100 scanner or the $3000 can all extract the code.

Best bet wait and see if it comes back or your milage gets better. In the mean time check you tire pressure, fluids, etc just to make sure everything is to spec.

[shox]

yea ive done the basic stuff already :). so basically i need the light on to be able to know for sure? :S

[Oldsman]

All I can say is i had to replace my upstream and downstream sensors. they both went bad. But so did my cat.

If you think they are going bad take it to a shop and have them scan it and see if they find anything.

[johny_boy32]

just have them scan like olds said...the can find anything with the TECH2