O2 light on, not sore sure why.

[skittishsynapses]

So I just posted something about my brakes in the suspension forum, and of course, something new came up with my car. I was driving home and the 02 sensor light went on. The car's acceleration has been slightly off but I didn't think anything of it. I replaced the o2 sensor last year (thank you topless forums!) and had the Cat changed out last month because it failed emissions. Now, the roomie mentioned Cats and o2 sensors are generally replaced together. Could it be replacing the cat somehow messed up my sensor?

unrelated note, the plastic hose to the vacuum reservoir broke sometime recently...no clue when..I can just pick that up at autozone?

Any ideas on what's causing that light to go red? Thanks everyone!

[eric4321]

The o2 light will come on at preset milage intervals. If you follow the speedo/odo cable from the trans up it should lead to a small box. The box should have a reset button on it. Press that and the light should go out.

[skittishsynapses]

I'm currently at 116k miles.. well sans that my odometer decided to stop working for a few weeks and recently started working again. What are the intervals the o2 sensor light comes up at?

[eric4321]

Well I checked www.cabby-info.com and they say the interval is 30,000 miles. Now one other thing. I am fairly sure your car will only have one o2 sensor and it is before the cat. The only thing changing your cat will do is change your tail pipe emissions.

[gull]

The reason catalytic converters and O2 sensors are usually replaced together is a common reason for a failed cat is an overly rich mixture caused by a bad O2 sensor. Replacing the O2 sensor at the same time is cheap insurance against melting down the new cat.

[skittishsynapses]

hum, wasn't told that when I replaced my cat. Tried to reset my o2 sensor and the light is still on. The replacement gap between the two is about...10 months. So gull, your vote is for a new o2 sensor then?

I went over the previous owner's smog tests and the cat is slowly gotten worse and worse. When I got the car she failed smog, replaced transmission at the word of mechanic which sure helped but wasn't the cause of the failed smog test (figured that out in retrospect but that's okay, she didn't shift into 2nd anyway!). When she failed smog again this year, the cat was replaced. Last year I had the spark plugs, distributor cap, and a few other things replaced along with the o2 sensor.

[gull]

The O2 sensor light doesn't tell you anything about whether the O2 sensor is working. It works entirely off the odometer.

It's difficult to conclusively test an O2 sensor. You can determine if it's entirely dead, but that's about it. If you're suspicious it's best to just replace it.

[skittishsynapses]

also worth noting is my odometer went nuts a month ago and stopped counting for about 300-500 miles. It then went back to normal (at least the miles worked, the kilometers rolled nonstop). Then 4 days ago, it decided to read at 250k miles (up from 118k). It now reads 300k+. I'm guessing that has something to do with my o2 sensor not working, seeing as I got the red light about a month and some ago. I just had never put two and two together until now.

[Briano1234]

also worth noting is my odometer went nuts a month ago and stopped counting for about 300-500 miles. It then went back to normal (at least the miles worked, the kilometers rolled nonstop). Then 4 days ago, it decided to read at 250k miles (up from 118k). It now reads 300k+. I'm guessing that has something to do with my o2 sensor not working, seeing as I got the red light about a month and some ago. I just had never put two and two together until now.

No that is a sign that the odometer gear is probably broken. It is the little gear inside the speedo, and it is probably cracked a little drop of super glue can "fix" it if it is slipping on the shaft.

[kamzcab86]

Tried to reset my o2 sensor and the light is still on.

You may not have pressed the reset button in far enough.

To test the oxygen sensor (and more): http://cabby-info.com/cis.htm#Sensor . Before taking a CIS car in for emissions testing, you should always get the car up to operating temp and check the duty cycle (air-fuel mixture); adjust it if need be. Also, check the timing.