No codes in for 3 years (O2 sensor replaced in 2022). Car is running like a clock and check engine light came on during an unusual warm day from where I am from (90F). A number of re starts and drives, it continues to stay on. Car sounds correct exhaust wise, no change in power band and power is not diminished in any way, no weird noises and no smelly exhaust so not thinking the Cat. Used the OBII and it pulled up the P0420 code and asking it diagnose it just gave me a bunch of stuff from filter, to exhaust leak to cat ..etc including filters ..etc.
I service the heck out of this vehicle via the dealer and OCD and having everything freshened up. .
Before I bring it to the dealer (have warranty), should I get rid of the codes and see if it stays away and maybe its a was a one time blip or leave it coded and bring it to the dealer next week. If it comes back it will be at the dealer pronto.
Thanks in advance.

 

Leave it coded. If you bring it in and the codes are clear they won't do anything. You're also on the edge of the 8 year warranty period for cats. If it were me, I would take advantage of as much of the warranty as I could.

Edit:
As a bit more info since I just went through this whole mess of replacing both of my cats outside of warranty (ouch). It takes two "fail" flags for a p0420 to go from pending to permanent. It takes many consecutive passes for the code to clear on its own (Four I think?). If you get a fail in between any of those consecutive passes, the code stays permanent and it starts over again at zero. You can probably squeeze more life out of your cats with a cleaner or maybe even get the code to go away if you just clear the code, but the fact that it came on means they are on their way out. If you turn a blind eye now, you'll be outside the warranty period and paying out of pocket which isn't exactly a fun way to spend money.

 

Thanks for the info and it is helpful. I just confirmed that the original owner (who is a friend) had the CAT replaced under warranty in Sept 2019. That might explain the code that says permanent when I checked it out. Could it be a legacy code that was there from back in 2019? I had just filled up with fuel and it was about 10 minutes later that the code came on. Could it be just the gas cap is an issue? When I clicked on delete codes the evaporative message came up. I did not delete. After a bit the other messages showed up. Trouble is I am days away from getting a gas cap for an F-type where I live... Love to try the cap and if it goes away all is good. Still will bring it in this week so I won't clear any codes.

 

A few years now, I had a P0420 on our F-Pace. I Replaced the rear (final on behind the cat) O2 sensor and it fixed the issue. It was an easy ten minute job on the F-Pace.

After about 2015 most EMSs started using the permanent/pending/ active fault systems on certain (not all) power train faults, the ones directly related to emissions faults as a way to foil those who would delete codes w/o fixing the fault when they had the car for sale. The permanent codes would remain until there was a certain number of pre determined ignition cycles w/o the fault then the ECU was programmed to remove the permanent codes.

 

If you had the CEL light up, then it is not a legacy code. Permanent codes are not stored legacy codes, a stored code could be, but not a permanent one. I cannot comment on the gas cap thing since I haven't dealt with that before. I would think a evap code would be a totally different number than a p0420. P0420 is pretty much exclusively the exhaust system.

 

P0420 is catalyst inefficiency, and is measured by the difference between the sensor just ahead of the cat and the one just behind. Since O2 sensors are a known issue, I'd suspect those first. Since you don't know how long the code has been there and you got a CEL about ten minutes after filling up, the gas cap is a likely culprit there, especially since you mention an evap code.

It's quite possible you've got two problems. I'd remove and reseat the gas cap and see if the CEL returns. On my year, the cap will click with it's tight enough.

 

A p0420 is not an evaporative emissions code, Those are more like P0456, P0442, etc. and can sometimes be caused by forgetting to tighten the gas cap.

You might have been confused by the message in your scan tool screen - "emissions related". All (or any) power train fault (any P-codes) are emissions related. At least to the EPAs they are. Any failure of any system in the power train that causes it to operate less than 100% as designed is considered to impact emissions.

This Jaguar engine series has always had problems with the OEM O2 sensors that were used in the system. P0420s/P0430s (and their families) are (were) pretty common. When I had mine, first a P0420, I replaced the back O2 sensor with a NON OEM, then less than a month later I got a P0430, same thing on the other side, replaced it with a non OEM sensor and I have not had a recurrence now in 5 years.

 

I wanted to give an update to this thread as i read so many that when the owner gets their issue resolved they do not bother coming back to advise what was conclusion. So my dealer stated it was the Cat, and for about a week I continued to drive it and the light stayed on. I ordered a Cat which is around $2200 USD as they stated it is a special order from the supplier across the country and need to prepay. Once it arrives they will charge me about $300 for the labor to install late this week. On one of my reply's on this post, I had stated the light came on after I had just filled up (Esso 94 octane) and was curious if maybe it was bad gas. Well drove it these past few days until the tank was near empty and filled up with a my normal gas station that I use (Petro Canada 94 octane), and of course within 20 minutes or so the engine light goes off. Have driven it the last two days in all types of conditions from high speed, traffic every variance I could think of and it continues to stay off. Many off and on starts since the light went off and again nothing. I will call the dealer tomorrow as to maybe they wrongly diagnosed it or just assumed it was the Cat. May have to pay a restocking fee but really don't want to have a cat around that may never be needed.
Could bad gas really cause this? It did not drive with any issues from stumbling to lack of power ..etc. so really bizarre.

 

Out of curiosity, how many Kms are on the car? Did you own it from new?

Hopefully it is just the gas and the dealer doesn’t give you too much of a problem with expensive restocking fees etc.

This said, these cars are notorious for going through CATs with all the crazy popping and banging so it’s a matter of time. Tell em’ to keep it on the shelf for ya ;-o

 

@RobMar So the 8 year warranty on cats did not apply here? Why did you have to pay for the part and labor?

 

That’s a really good point, but wouldn’t you still at least have to pay for the labour even if the part cost was covered?

I thought it would have to be inside the base bumper to bumper warranty for labour to be included.

 

35,000 km. Close to new but not quite.

 

Nope, missed warranty by about 5 months unfortunately.

 

Oh that's a shame.

Just to be absolutely sure - you are seeing P0420 as both an active and permanent code? The permanent code is for the right side (Bank 1) - is that the cat that was replaced a long time ago?

Is the new code Bank 1 as well?

I would hate to have you pay for a new cat when a new O2 sensor is all you need.