Ripped the O2 sensor wiring off last night wheeling. I thought they operate on resistance (doesn't matter what orientation the wires are in) so I just hooked it back up. I still have a check engine light. There are 2 wires coming off of it, both are white. On the wiring harness they are black and grey. Any ideas?

 

There is actually a voltage on the O2 sensor, so yes, polarity does matter.

 

Is this for the '99 you have listed? If so, should be more than 2 wires. '99 would have a heated O2 sensor. Polarity wouldn't matter for the heater wires.

 

Odd, i'll go out and grab a pic. This is the O2 sensor after the cat, I guess I didn't think about it before but there are more wires on the Jeep wiring harness, but only two on the O2 sensor harness.

 

Hmmm, I thought the downstream sensor was heated, too, but I could be wrong.

 

Alright, O2 sensor side, gray and black wires to two white wires

And the other side definitely has four wires, pretty odd.


Here's a shot a bit further away

 

Looks like maybe a universal sensor was spliced to the original plug.

 

Maybe. After doing a bit of reading though I guess there's supposed to be 2 whites, a grey and a black. Maybe some wires got ripped out entirely? Looks like I might have to buy a new O2 sensor lol.

 

That might be best. I don't think they're too expensive.

 

Yeah I just went and checked, there's definitely holes for the other 2 wires in the O2 sensor, but no wires coming out. I cut the wires I spliced back together, hopefully nothing was damaged being mismatched like that.

 

New O2 sensor is in. No difference in how it runs either lol I guess I'll see if my gas mileage changes

 

The downstream sensor's purpose is to tell if the cat is doing it's job. The upstream sensor will affect mixture.