I've been having an intermittent P0420 code that my OBD II scanner said is right bank cat. For more detail, I paid $122 to my Jag dealer for a complete scan and diagnostic.
They recommended a 3-part top engine cleaning for $460 that cleans the fuel injectors, and a spark plugs replacement for $644. If that failed to clear the fault, then they talked about replacing the injectors and fuel rails for a dastardly fee.
I had been preparing for a transmission fluid and pan replacement so had sprayed the T27 bolts with blaster. They thought the pan and the cooler lines were leaking and also recommended the pan and cooler lines replacement for $1,891. There is one joint in one of the cooler lines that is weeping slightly, but I don't think it needs any help right now.
At any rate, I ran some Lucas cleaner through the fuel lines and this evening changed the plugs. My engine light went off, hopefully for good this time.
I found NGK iridium plugs at RockAuto for under $60, so what a thrill to get my problem fixed for $1,000 less than the Jag dealer wanted. Hurray for DIY!

 

Congratulations kbeachy!

You're my kind of Jag owner!

Cheers,

Don

 

Did you laugh at the dealer and their outrageous diagnosis/costs?

 

I cleaned both right bank oxygen sensors, and that seems to have taken care of the problem. It's not throwing the code anymore. So maybe it means the cat is not cleaning the way it should, but at least for now it seems to be okay. I'll wait and see what develops.

So much for the dealers diagnosis of fuel injectors and spark plugs.

 

Update on my P0420 problem. The code came back, so the oxygen sensors had nothing to do with it. The dealer had diagnosed fuel injectors and spark plugs. I put in a set of GB Reman injectors from RockAuto. Indeed they were what solved the problem. Code went away for good, and the catalytic converter seems to be fine. I recommend the GB Remans to anyone needing fuel injectors.

 

Hi kbeachy,

Thanks for reporting back with your success! It seems counterintuitive to me that new injectors would solve a problem indicated by P0420, since the X350 Workshop Manual states that P0420 indicates a problem with the right hand catalytic converter efficiency. Is it your understanding that one or more of your injectors was leaking? Clogged? What injector behavior would lead to reduced catalyst efficiency?

Thanks for any additional information you can provide.

Cheers,

Don

 

Don,


The diagnostics showed that 7 of the 8 cylinders were misfiring, which was probably causing the cat inefficiency. They were likely clogged, which the dealer said is not unusual. I had also not been running high octane fuel.


The dealer wanted to do a 3 part upper engine clean that included cleaning the fuel injectors without removing them. I opted to replace them. I'll attach a copy of the diagnostic report.

 

So if I understand the report, you had 12 DTCs, not just P0420? Have all of those codes been resolved now?

 

I have an OBDII scanner that only detects some codes once the engine light comes on. The engine light stays off now, so I'm not able to detect any codes.


I haven't had a more sophisticated scan done since the fuel injector replacement, such as the dealer's scan that had the 12 DTCs listed.

 

Congrats Mr. Beachy! Does your jag run any differently with the rebuilt injectors? It seems to be a fairly common malady with our era jags.

 

Hi Ross -
I didn't think about it not running well before they were replaced, even when 7 of the cylinders were misfiring. But I can tell now that it's running more smoothly, and getting 1-2 mpg better.
Changing the injectors myself is another story! I dropped one of the clips that are used to secure the injector to the fuel rail and couldn't for the life of me find it on the floor or in the engine compartment, even after an hour of looking. So I had to wait on one to come in at Byers Jaguar. It turned out actually to be a good thing though because it alerted me to the fact that I wasn't putting them back on right. Don't need an engine fire!
The most challenging aspect was getting the new injectors seated properly in the engine block and in the fuel rail. The right side fuel rail also has a pressure sensor connector on the end of it that has to be removed in order to manipulate the fuel rail. That was hard to work with because the electrical line had no slack. At any rate, if I had to do it again it would go much faster!

 

I wonder how many chapters this P0420 book has?!


Today, two weeks and 700 miles after changing the fuel injectors eliminated the P0420 code, it's back. My heart sank. I'm going to have the codes read again to see what more is going on than my simple OBDII scan gadget will show. Any ideas, anyone? Thanks.

 

Have you changed the cat?

 

Hi kbeachy,

Sorry your code is back. That particular code is one I'm trying to sort out on my daughter's and son-in-law's 2005 Nissan Altimas - same cars, same code. The Internet is full of speculation and theories about P0420, and there are plenty of accounts of owners who have replaced the cat only to have the code return. Below is a representative example of a list of possible causes of P0420. The approach I'm taking on the Altimas is to work through the easiest and least-expensive possibilities first.

• Leaded fuel was used where unleaded was called for
• A damaged or failed oxygen sensor (HO2S)
• Downstream oxygen sensor (HO2S) wiring damaged or connected improperly
• The engine coolant temperature sensor is not working properly
• Damaged or leaking exhaust manifold / catalytic converter / muffler / exhaust pipe
• Retarded spark timing
• The oxygen sensors in front and behind the converter are reporting too similar of readings
• Leaking fuel injector or high fuel pressure
• Cylinder misfire
• Oil contamination

According to a Nissan TSB, if certain tests prove inconclusive, the technician is advised to separate the exhaust pipe from the cat and to inspect the interior of the cat for deterioration of the catalyst. Given that you had 7 cylinders misfiring, are there other possible causes of the misfires besides the injectors?


Don

 

Mr. Beachy, just a thought- have you replaced any of the 02 sensors lately?

 

Believe it or not, I had a cat on hand to install. I waited what I thought was long enough that the cat wasn't going to need replacing, and I sent the cat back. Oh well, there went the return postage! I may have to re-order it.


What I'd like to do is have the codes read again to see if any additional codes are present to indicate why the cat code would be back. Options at this point are to replace the cat (but if there's something else throwing the code I don't want to ruin a new cat over time), replace the oxygen sensors, or something else. Hopefully any other DTC's will point the way. I want to be sure that the cylinder misfires are gone now that the injectors were replaced. It just seems odd that it waited 2 weeks and 700 miles to come back when it was on pretty constantly previous to the new injectors.


Thanks for your helpful ideas!

 

I was sent to a demonstration on converter efficiency codes and problems put on by walker exhaust systems and here is what they shared with us. They said 70% of converters replaced DID NOT need replacing. Converters only need replacing if the substrate inside is cracked or shattered, loose, or melted because of excess fuel in the exhaust system. Converters simply don't wear out, but they can be damaged. They said that you should do a upper end engine clean, carbon depletion or whatever you want to call, not a fuel injection cleaning as that is different. Fuel injection cleaning is when you remove the fuel line to the injectors, and connect a pressurized canister of highly concentrated detergent/fuel mixture to the fuel rail and run the engine off of the mixture in the pressurized canister. Use a carbon cleaner or detergent like seafoam threw the vacuum source or thru throttle air intake using equipment to meter a constant flow of the cleaner into the motor. These typically take around 20 minutes to complete, however you need to run this cleaner thru for a constant 40-45 minutes to get the converters cleaned out so you simply run the engine clean 2 or 3 times in a row with no pauses in breaks in between as the converters will cool off. They stressed that this needs to be done for 40+ minutes to be effective, and the motor should be held at a constant 2000rpms thru the entire process.

If you want to do something quicker that you can do yourself, I would try this:
Using the vacuum line method of cleaning engines with Sea Foam Motor Treatment - Sea Foam Sales Company

Many companies refurbish converters and resell them using a similar cleaning method. So if you do end up replacing your converter, don't throw it away, many companies (just look online) will buy it from you to refurbish. We have been paid $150 for used converters at my dads auto shop before. Sometimes they have paid us half of what the new converter cost for the old converter.

 

My local Jag dealer where I had a diagnosis done on the code wanted to do what they called a 3 part upper engine clean. Maybe that's what you're talking about, but I thought it was related to cleaning the fuel injectors as they thought they were clogged (getting cylinder misfire codes). I didn't want to pay them $466 to do that when I could put reman fuel injectors in myself for under $250. I'll check out the Seafoam.

Is it possible bad fuel injectors could put excess fuel into the exhaust system (one of the ways that you mentioned) and thereby ruin the cat?

My engine light went off again this morning. It was on a shorter period of time than before. I'll see how long it stays off this time, expecting it to come back.

 

pcar00,

Thank you for that very helpful post! Note that, at least on some previous Jaguar saloon models such as the XJ40 and maybe the X300, Jaguar has issued TSBs warning against running the engine at 2,000 rpm or higher with the transmission in Park or Neutral due to the potential for internal transmission damage (I assume the torque converter). I doubt the same applies to the X350, but it would be worth checking in advance to be sure before performing the operation as instructed.

Cheers,

Don

 

I had the codes read today, and the only thing that showed up was the P0420. So all the other DTC's were taken care of by replacing the fuel injectors. What I'm thinking now is that it's probably the cat or the oxygen sensors. My next step is going to be trying the Seafoam engine treatment to see if there are deposits in the upper engine or in the cat that can be cleaned out. If the code persists, then what should be done next? Oxygen sensors first? Cat second? Thanks -