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XJ California Exhaust System

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My MJ has the engine from a 2000 XJ in it, and it has the California emissions system on it.


I see two "mini-cats" just off the exhaust manifold, with pre and post cat O2 sensors.  What I do not have is a second "main" cat converter further downstream.


The FSM is contradictory here.  It shows a main cat like all the "49 state Federal" in place along with the mini-cats, but the wiring diagrams do NOT show O2 sensors associated with the main cat., only with the mini-cats.


So do the CA XJ's have three cats?  If they do,does the main cat have any O2 sensors?


i have to get the exhaust system right to pass emissions testing here in AZ.

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1 hour ago, Ωhm said:

R U A V6, if so, I don't see no DTC's posted for a 3rd cat.

A V6?    A 2000 XJ never came with a V6, only the 4.0 in-line six.


My FSM lists the following codes:

P0143 (M)    1/3 O2 Sensor Shorted To Ground

P0144 (M)    1/3 O2 Sensor Shorted To Voltage

P0145 (M)   1/3 O2 Sensor Slow Response

P0146 (M)    1/3 O2 Sensor Stays at Center


Since they talk about O2 sensors 1/1 and 1/2, as well as 1/3, I thought it might be a sensor related to a third cat.


I am still confused.

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Thanks, "JeepDriver" and "Sinkrun"   Those two details explain a lot that seemed a little unclear from the FSM.


So it looks like I have all of the O2 sensors and wiring needed, along with the mini-cats.  What I don't have is the "main" cat located downstream between the trans. mount and the muffler.   I guess I have some shopping to do if I want to pass an emissions test.

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2 hours ago, gogmorgo said:

Just curious, has any AZ emission tech actually told you your exhaust isn't compliant?

No, not yet.  I have been debating this myself.  Maybe when they "sniff" the unit (which is registered as a 1989), they will find it complies.


The only thing stopping me right now is that the vehicle has no brakes, and I am waiting for parts to arrive to complete that task.


Maybe I will take it to the emissions test station and see how it goes....

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On 7/22/2018 at 11:22 AM, JeepSchmidt O'Guinness said:

I thought there was something offered like diagnostics procedure's before you actually do the inspection test which can label your title as a gross polluter?

If there is such a thing, there is no information on it anywhere on the Arizona DMV or Arizona Dept. of Environmental Quality websites.


I cannot find any exceptions for vehicle age, etc. and I am unlucky enough to live in an area of this state that requires emissions testing.

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My address is in the area that requires an emissions test.  If I lived 2 miles east of here, I would be exempt.


Since I am not roadworthy right now without brakes, I am not too concerned yet.   I will probably take it in and have it tested with just the front two California cats, and see if it passes.  I will also investigate the exemption mentioned in the link by "Ohm"


Standby for more details later.

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