Need help locating secondary o2 sensor.
I'm frustrated and can't find what the deal is with my 2000 miata. It's throwing code 0421 that's related to the cat. Problem is this car has a non factory cat and the second sensor is right behind the pre cat and not below the car where I find in most cars.

Is this right or did someone jack this car up. Please help as my friends and I are standing in cold trying to find answers.

EDIT: that was such a noob thread haha but I found what i needed. I proceeded with the spark plug fouler trick. Now i'm off to run the car for about 80 miles to have the ecu tell me if it's ok or not.

 

Are you sure the one after the precat isn't a wideband sensor? The downstream sensor is in the mid pipe near the axle, facing upwards. The wiring runs into the car under the carpet.

The aftermarket cat is probably not as efficient as OEM and the downstream o2 is not happy.

 

What??? I don't remember my '99 having any secondary O2 sensor near the axel...
Why would it be near the axel anyway? That's all the way at the back of the midpipe!!!

 

Flounder there is a Cali spec and fed spec. Heres mine



Thirdgen I have a nb1 lip slightly damaged off you are interested but how would I ship it?

 

My car is / was, a cali spec. Same pre cat and O2 setup as yours. 1 O2 sensor marked as #6 and 1 marked as #3.
Do you have any photos of the NB1 lip? You could just wrap it in plastic and put a shipping label on it, that's what I'd do, with full insurance of course.

 

What ship company would handle it?

 

UPS would...USPS might do it too...also most likely Fedex?

 

That must be it.
My upstream is in the dp along with my WB, and my downstream o2 is right behind the cat. You crazy cali cars!