I recently had the check engine light on my '06 Super V8 (107,000K miles) come on and used my $18 code reader to find out it was the P0420 code.
I've read several threads here about what that could include. My first question is would a better code reader give me something more specific? I will get a better reader and am also reading up here about which one would be a wise purchase.

I like to think I'm a little smarter than when I was younger and got a hunch about what part may be the culprit and replaced it with a new one only to find out my hunch was wrong. Also, the price of parts on these cars makes that approach very unwise.

I'm just trying to get an idea of where I might start to resolve this issue in a sensible manner.

 

This code refers to catalyst efficiency. I've attached some information from DTC book.


Have you had any symptoms with the car, or just the check eng light with P0420 logged? You need to check to see if you have any misfire codes logged as well, and also when was the last time you changed plugs, fuel filter, etc...


Could also be catalytic converter failure as well - have seen this many times on XJ's and S-Types. They break up inside and eventually become clogged.
One might discolored as compared to other side.

 

Hi and thanks for the quick reply. No problems at all with the car until the light came on. I've owned the car for less than a year. The records show new plugs at 90K but I am unsure about the fuel filter. No oil consumption so I don't think that would be the cause.
I will get underneath the car tomorrow and have a look at the catalytic converters.

 

This is the more advanced code reader that I use on my Jag - https://amzn.to/2DncONB I got mine for $50 less because I found a used one for sale.

Anywho, P0420 means the converter's efficiency is degraded. It really should be failed by 107K miles, but usually they fail because the engine is not running right.

Get a good scan tool, monitor your oxygen sensor readings and fuel trims for some insight.

Some more tips I found at https://www.p0420.com you could try Cataclean?? Worth a shot I suppose before spending big money. But the scanner I would say do buy that one or a comparable one as it will be handy in the future.

 

Thanks for the advice. That webpage is very helpful. I thought trying the Cataclean first may be worth a shot but the reviews of it are lukewarm. It seems like a 50/50 proposition so probably worth a shot at around $20.
Are you saying converter failure at 107K is not unusual or only because of improper tune?
I will get a better scanner. The one I have was dirt cheap and helped on other vehicles but the Jag is a different animal and requires more attention.
By feel, the car has run great since I got it. The only thing I have noticed is a slight stumble when I first pull away on a cold start. Once past that it ran great and felt like full power. It probably was not actually full power so I will look into it more closely and a better scanner should come in handy.

 

I was lucky found an iCarsoft i930, Jaguar, Land Rover reader, on sale for $99.99, but by opening an Amazon credit card account, (NO FEES) they knocked $50 off the first purchase. Delivered to my door for $56.76, a really great deal, there are better readers out there, but not for this money. Works on both my Jaguars, reads, & erases codes, that never popped up since i owned it. It told me my front shocks were leaking, well not anymore, when it was first bought, they were. But never told me on the screen, with any kind of warning.

 

Knowing how the system works, in my opinion, if you just got a P0420 then the Cataclean has a greater likelihood of helping since the problem will still be relatively minor. If you drive too long with a misfiring engine it will destroy the converters and then in that case the Cataclean is a total waste of money. My $.02.

 

A little more detail on that DTC and other causes

 

The light went out on its own a few days ago and seems to be staying off - so far anyway.
I bought a bottle of an additive called Oxycat, similar to Cataclean and better reviewed and could be shipped to my location unlike some others.
I just added it since the light went out so hopefully it will do its thing. I figure the light going out on its own means the fault wasn't that severe and the additive and all proper maintenance will keep it from returning.
I did get a better code reader and hopefully now will use it to monitor things rather than read fault codes.