O2 sensor dying?

[2GturboTALON]

During night driving my A/f guage stays in lean but during the day it is in one spot on stoich and stays there till WOT. Is my O2 dying? how do i check it?

 

[gs-t spidey]

The only way to check if your o2 is dying is to use some type of scanner. If you have a datalogger you can use that, if not then you need to have somebody scan it with a diagnostic scanner. When you do this look at the o2 volts. They should jump around between 1 and 9 volts. This is normal. If it doesn't then you probally need a new o2. usually your ECU will through a code if your o2 is bad because you will be running either to rich or to lean. You can go to auto zone to get your car scanned. I've heard that they do it for free