Was going to get it inspected tomorrow and of course the MIL comes on today. Scanned the codes and I have a P0430 which translates to Catalys system below efficiency threshold, bank 2 (which I beleive is the pasenger side in the US).

Car has 125k on it, I just replaced a very dirty air filter a couple hundred miles ago. Checked my work and everything is sealed up tightly, no obvious intake leaks. Car runs smoothly, plenty of power. I drive it conservatively but periodically run it to 3500-4500 because I can't get enough of that sound. Passenger side front O2 sensor was replaced about 1000 miles ago by myself with a Denso replacement (which I beleive is the factory brand, or made by the same manufacturer?). I always use 93 octane, no obvious oil or coolant consumption.

So are there any remedies I can or should try first that will get me more than a week of success or am I just looking at a new set of cats for the pasenger side at this point? Like will a new rear O2 sensor potentially resolve this since it has to work with the front one to measure the catalyst efficiency? Are there voltage or current values I can cehck with my scanner (it does live data) that might indicate a bad sensor for example? I assume those catalytic converter cleaners in a bottle are snake oil, or are they actually effective? What about a few knocks with a hammer on the cat to shake loose debris that might be clogging it up and then a few runs to the redline? Basically is there a less expensive way to help resolve this that isn't going to result in a ruined motor full of cat debris?

I did capture some live data on the 4 O2 sensors at idle, engine still warm from driving 2 hr ago, but not full operating temp. Voltages on both bank 2 sensors looked comparable to both bank 1 sensors to me, but honestly I don't know how to interpret this data.

I recently did the passenger side valve cover gaskets (with plug well gaskets, plug wells were fairly oily but not crazy bad...cleaned them out as best I could before reassembly and cleaned the plugs and reinstalled, plugs looked good, though not new.

Thanks!

 

Maybe replace the downstream 02 sensor, clear the code again and then drive the snot out of it to get the cat hot and see what happens.

 

So I cleared the code this evening, just ran it on about a 50 mile loop, half highway and half backroad, some stoplights, etc. No MIL as of yet and all but one of the monitors have flipped to ready status, including the catalys monitor. So MAYBE I'll be lucky enough for it to go ready tomorrow and I can get my sticker while its cooperating...then I've got plenty of time to sort it out. Can I presume that driving it harder will be less likely to get a repeast of the code because the cat is running hotter?

If it comes back I'll do the downstream sensor I guess, the Denso ones are only $55 for the back ones. But now I'm realizing I'm getting my banks confused...bank 1 is the right side, bank 2 is the left, so this error (when it returns) is coming from the side I've never touched.

I've located a few threads for 0430 errors, most seem to be paired with 0420 codes, which is the same problem on bank 1, which would lead me in a different direction as I wouldn't expect both sides to go our at the same time. One guy with an XKR had a 0430 only and he resovled it with just a front O2 replacement. Other threads I see some techcertified members posting that there is no way a faulty O2 sensor is going to trip a catalyst DTC and there are other members who have resolved 0430 DTCs at dealers who replaced both sensors in that bank, so it might actually be the cat...or it might not.

Rock auto has Davco cats for sale for the 02 XJR, priced at under $500...should I ned a new cat, does anyone have an opinion on these? Not ready to buy one yet, but might as well do the research now.

 

The downstream 02 sensors are catalyst efficiency monitoring sensors. To the best of my knowledge, these don’t adjust air/fuel ratio. In my opinion, after the engine is fully at operating temperature, running the car down the road and getting on it hard to get it to redline at the top of first and second gear a few times should be enough to burn any carbon buildup (if it has any) off of the cat. If the code still pops up after all the tests, I’d replace the sensor then clear the code again and wait until it passes all the tests. If it doesn’t pass the test after all this, I would monitor the LTFT of that bank and see if you might just have a leaky injector on that particular bank. Hopefully your only running premium fuel to help keep those injectors cleaned.

 

I've only put 93 in the tank, to be fair I've only had it a short time, put about 1300 miles on it so far and obviously no way to know what was run in it before. Maybe a bottle of seafoam in the tank is worthwhile?

Hopefully the last test will go ready tonight and I can get my sticker tomorrow, then I'm off the time crunch if the MIL reappears and I can take my time with a diagnosis and maybe learn something new about the car.

Thanks for the advice Addicted!

 

Jaguar only recommend BG44 fuel system cleaner, give that a whirl..

Having had a couple of O2 sensors go open circuit, just replace it, do a hard reset and that side's done for another good few years.

 

Some drivers have been successful placing those pipe spacers ahead of the O2 sensors.
It may keep the light from coming on, but either the cat is partially blocked or the sensor
is bad and will eventually need to be addressed.

 

I would replace the downstream O2, hard reset, and let the car relearn the monitors. If that fails use an O2 spacer and that should do it. I wouldn't replace the cat until you absolutely have to, usually the spacers will buy you lots of time. I've had one on my 2004 Impala for 3 years and nearly 80k miles now and light has never come back...good luck.

 

Use an O2 spacer on the rear sensor? Is this a commonly available thing?

I cleared the codes and the CAT montior went to clear and my inspection appt is tomorrow so obviously I'm not doing anything with it for now, no sense in asking for trouble. But its likely to come up in the future so I might as well be prepared if it does.

 

Yea, pretty common to use ont he rear sensor with an aftermarket or slightly clogged cat. I've had aftermarket cats on my supercharged 3.8 GM vehicles for years and always needed to run one. It's basically jsut a pipe adapter that pulls the sensor out of direct contact with the exhaust stream, I think I used to buy mine on Ebay. Pretty common.

 

yes, the 02 spacers are pretty common, with some going so far as to have a mini "cat" that gets placed right before the sensor. Its a work around, generally for people who run sport cats or who have poor performing cats.

Worst case, I've free-aired my rear 02 sensor on my porsche track car with no CEL issues, so it could be a temp fix if necessary.

 

https://www.wish.com/product/5ff28c2..._wcB&share=web

This one is available and shows how to use it. M18X1.5

 

Cool, thanks very much! I'll try this out on my kid's Saturn, currently throwing a P0420 and I've replaced both O2 sensors. Saves me a few hundred bucks and a bunch of rust in my face swapping out the cat.

 

Try catalytic and exhaust treatment...in gas tank.