Exhaust system for california Model
 

Hello All:

The callifornia miata has a 2 cat converter exhaust system.
Does anyone know how many O2 sensors there are in the exhaust system?
I know there's one before and after the first cat (the one closer to the exhaust manifold)
However, is there any O2 sensor after the second cat converter? (the cat between the first cat and the resonator)

Many thanks in advance !!

RE: Exhaust system for california Model
 

Only show the 2006 and later MX-5 to have a warm up CAT at the manifold. 05 and earlier only see a main cat down in the middle of exhaust. Only shows 2 O2 sensor in either case though.

RE: Exhaust system for california Model
 

That's wierd, I have a 2000 Miata, and it has 2 cats.
I got code P0421, P1345 so I brought it to 2 diffrent mechanics for qutoes.
one of them says that the O2 sensor behind the second cat (the one away from the exhaust manifold) is busted.

I'm all confused now.

RE: Exhaust system for california Model
 

You are right icen and I was wrong.:eek: Did not dig quite deep enough into the warm-up CAT usage. Sorry about the confusion[:@].
Mazda did use a Warm up Cat just after the exhaust manifold and a Main Cat further down the exhaust for Calif regulation for 3 years only from 1998-2000 model year. In 01 the warm up cat was discontinued for California cars. The P0421 is a catalyst efficiency fault code. Have never seen a O2 sensor problem set that code except on a few Millenias and Mazda recognized the problem and came out with less sensitive sensors. Even then replacing the sensors with updated did not fix as car would come back in a couple of months with same code stored. Your catalytic converters are covered for an extended emission warranty of 8year/80k miles if you are still within that range.

P0421
 

that means, the code P0421 is for the 1st. CAT attached to the exhaust manifold of 2000 NB mazda miata.?