How do you know when the O2 sensor is bad and is there anyway to test it?

 

You'll get a "Check Engine" light pop up. Then you need to have a code reader to pull the code. There's hundreds of codes, so if the one that gets pulled is for the o2 sensor, you're all set.

You can also use a multimeter to check the OHM resistence or something like that. You'd have to find the spec on it, know how to read a mulimeter and know where to attach it. I've seen posts talking about it, but it's pretty "technical" stuff.....

Good Luck.

 

MtichF150 is bang on. You will get the "Check Engine" light on the dash lighting up.

I've had a few of em go in the last 4 years and they always pop the light. 1st was on warranty, last 2 weren't . . . and they resulted in a nice little bill