You guys recently helped me do a full tune up on my 98 s-10 4x4. Now I am having another issue. My CEL came back on and it's throwing another code (the first inspection fail was due to the light coming on and it threw spark plug #5 code, so I replaced all the plugs when I did the tune up).
By the way, the tune up was a success, it has run just fine for almost a month with no issues. But the light is back on. I wasn't able to get the re-inspect because I have been waiting on a replacement driver side mirror glass. Yes, the other reason they failed me was the mirror had a 2" crack.
Now the code it's throwing is the 3rd O2 sensor. I disconnected the negative cable for a while and re-connected it to see if the light came back on, and it did. My questions are:
The sensor is $53 and I don't have it so can I use seafoam, just as a temp fix?
Can I trust the code and just replace the sensor? I mean, do these sensors really go bad??
I was told there are 4 O2 sensors on this thing. How often do these need replacing?

 

Yes they do go bad. They will usually last about 100,000 miles. Some last longer, some do not. Every time I saw a code for the 02 sensor, the code went away when the sensor was changed. Make sure sure you replace the sensor with correct one. A downstream sensor needs a new downstream sensor. An upstream sensor requires another upstream sensor.