I have a 2006 XJ8L that i just found out is a California spec car in New Jersey. The Cat is bad on the pass side, so I ordered a new cat that is 49 state legal. will that work on my car and NOT cause the Ck engine light to come on? New Jersey is not as strict as Cal. so a 49 state Cat would pass here. Any one know for sure?

 

You should be fine for NJ. They basically look under the car with a mirror and as long as the CEL is not illuminated and your emission monitors have run, your good...

 

would a bad O2 senders cause the bad cat code to come up?? and do you have to use Denso units instead of Bosch? i used Bosch O2 sensors NOT Denso.

 

If you are unsure about the catalyst, check with the state you live in as several in the Northeast U.S. have adopted California emission standards.

In my experience, if the vehicle has the MIL on and the stored code is P0420, it cannot be fixed with replacing the oxygen sensor(s).

 

I also have PO420 code and a check eng light ('07 XJR 90K miles); Bank 1 (RHS)

In researching this forum, seems that the RHS cat is a semi frequent X350 failure. I did not find anyone successful in fixing problem by swapping or replacing O2 sensors

Are the OE sensors not Denso? Why use Bosch? Are they more tolerant?

The one thread I found actually reporting, the RHS cat was obviously bad upon removal

Looking at aftermarket cats on Ebay, I am tempted to replace both sides with (weld in) ~200 cell (higher flow) cats. Anyone done this?

 

I expect both makes work fine.

I like to check the fuel trims in case one side is a little out since that can gradually damage a cat and then the code flags. (Not too late to look at the trims so you know what they are.)

 

This is not necessarily true. Especially if the universal is used. The lambda voltage from Bosch sensors, can cause significant issues. Wideband voltages, which is what is currently being used by Bosch's current design has caused problems for numerous vehicles. Denso's are the OE and cost $48 for downstream, and about $100 for upstream.

 

If you were to swap downstream sensors, and the code didn't follow the sensor, then the cat is the issue. Generally, misfire causes raw fuel to be dumped into the cat, where it ignites and melts the cat, or you can poison a cat with silicone or antifreeze.

 

Thanks. Just FYI, I did try swapping the downstream O2 sensors; still PO420 bank 1 (RHS). Hence my search for a replacement cat

Regarding fuel trims:

I have a cheap OBDII/CAN reader, but don't think it is capable of much other than generic code reading. I have used VAG/COM (on a laptop) for german cars; it is excellent

What is the best DIY diagnostic system approach for Jags?

 

I have a dedicated laptop for my usage, and use Jaguar's SDD, but there are quite a few devices out there to pull info from the ODBII.

Sorry to hear about your cat.

 

An elm327 can do live data, so fuel trims.

 

I always replace the 02 sensors with the same brand, or whatever it needs to keep the same brand on the same side at least. i.e. bosch pre and bosch prime sensor. I read a test on response rate and frequency and different manufacturers respond differently, so that can send a code. fwiw.