Check engine lite

I have a 97 Olds Achieva and my check engine light came on this mornig. Gas cap is on good, and car is running fine. I just filled it up - so I don't know about gas mileage yet. I have read alot about the 02 Sensor. Where is that, and how can I test it. Also how long (appox) before I need to get this fixed? Will it start running rough, etc?
Thanks, you guys are great!:worshippy

The first thing you need to do is get the computer scanned to see if it really is the O2 sensor. Take the car to Autozone. As long as the light is on they will scan it for free. It could be something altogether different. You chould have a misfire, an evap system malfunction or it really could be and O2 sensor. You don't want to start replacing parts without knowing what the real problem is. There should be at least two O2 sensors on your car. One should be on the downpipe behind the engine and the other should be just behind the catalytic convertor. If you find that an O2 sensor is bad don't buy a Bosch sensor. They are junk.

The first thing you need to do is get the computer scanned to see if it really is the O2 sensor. Take the car to Autozone. As long as the light is on they will scan it for free. It could be something altogether different. You chould have a misfire, an evap system malfunction or it really could be and O2 sensor. You don't want to start replacing parts without knowing what the real problem is. There should be at least two O2 sensors on your car. One should be on the downpipe behind the engine and the other should be just behind the catalytic convertor. If you find that an O2 sensor is bad don't buy a Bosch sensor. They are junk.in new orleans area auto zone will not check anything newer then 1994. i tried. anyway a good local auto-electric shop here said $65. to diagnosis it with light on. my SES light only comes on at highway speeds while climbing a bridge and stays on.

Too bad you don't live in Central PA, I would scan it for you for free! You can actually buy a reader for less than that and do it yourself. Although you won't be able to clear the light. If you have an advance autoparts see if they will scan it for you. Most of the parts stores have the capability to scan this car for you they are just too lazy.

I agree with GTP dad. Either the person at Auto-Zone was being lazy or someone at that location broke their OBD-II scan tool and they haven't replaced it. Try Advance, or if you have a Cottman Transmission shop in your area, they also offer free scans, including ABS and Trans codes that Auto-Zone and Advance cannot do. I would report that Auto-Zone store to corporate, as that is not their policy as far as customer service is concerned.