Good Evening,

New here so nice to meet everyone. I recently bought a 2016 F Type R with 61K miles. Not too long after I bought it the cat started throwing codes P0420 and P0430 at the same time. Took it to Jaguar and they claimed that all the O2 sensors are fine but the cats are failing and need replaced. Since I am out of warranty it is an $8K fix. Very upsetting for a vehicle I have owned for less than a month. My extended warranty doesn't cover catalytic converters either. That being said I have some suspicions that the issue maybe something else.

The cars LTFT are very high (14-18%) so I have a feeling the vehicle is running rich causing the codes. Jaguar claims theres no leaks but I doubt they fully checked it and defaulted to OBD Data.

- Has anyone dealt with it and any advice ?
- Could an MAF issue trigger this
- Thoughts on used Cats vs. VAP High-Flows ?

Thank you

 

I just went through a very similar experience. I reported to the dealership a P0420 code, MIL on, LTFT >+10% B2, >+12% B1. They checked absolutely nothing. Their >US$250 diagnosis was only to show me the DTC P0420 and required $4k replacement estimate.

I informed them again that CATs cannot cause their own failure. That I suspected the overly rich air/fuel condition would be a good place to start working to identify the cause of the CAT failure, if indeed the CAT is actually failed. They responded that the technician knows this particular code needs no further investigation, that the CAT is always bad and so must be replaced. I asked for the Service Manual description excerpt which lists OEM's diagnostic procedures. I then found myself in radio silence.

Your symptoms are similar to mine because both B1 and B2 are affected, albeit to a higher level.

To skip directly to the end of mine, I simply opened the hood to notice rodent pee and poop atop the SC. It was also clear a few electrical conductors were damaged; one stranded conductor was down to 3 remaining strands. I repaired this single conductor, a few drives later the MIL light turned off, then the car passed state emissions inspection. LTFTs are now typically +3.5% to +5.5% at normal cruise. My cause is not likely to also be your cause.

I knew that because both Banks were calling for too much fuel, the cause was unlikely to be anything isolated to a single Bank. Your situation doesn't allow this shortcut, because you're missing the long term "no codes" prior condition. Since you just recently acquired this vehicle, it's possible both banks have one or more problems each. I've seen cars generally neglected which had 6 of 8 sparkplug boots arcing to ground as the cause.

DTC codes do not turn on MIL until a series of events have completed. The p0420 and 430 codes must be triggered on two sequential operating events to reach "confirmed" status, which lights the MIL. It's possible these codes were simply cleared when you took possession, but it took several drives to light the MIL. A good scanner will show how many miles (and more) the car drove since DTCs were cleared. If this was done, it'll become necessary to verify all combustion supporting systems are operating correctly.

To answer your original questions,
Yes, a bad or dirty MAF can cause high/low/erratic LTFT. There are two MAFs, so each can only affect the connected bank. When I have a single bank problem, I always roll parts between the two banks to see if it moves or stays, if possible.
Aftermarket CATs are wonderful, but only if you know how to select properly. The folks at Davico Mfg. make a perfect CAT for 2016 F type, but there are many others. A new CAT only cost $200ish for my SVR, but I didn't need one this time. If needed, I was just going to order the CAT to weld it in my existing pipe.

Many will say generic CATs fail quickly or just don't work. Both are true if you never fixed the cause of failure. However, both are also true if a new OEM CAT were installed. When an unbent CAT fails, the cause is never the CAT.

I'm not familiar with VAP high flows. The OEM exhaust system on F-Types is not restrictive, so... I don't know why you'd want to dive into a redesign. I setup high HP chevy street cars with larger CATs as part of overall power upgrades. Except for power adders, I've never seen ANY single mod improve any dyno result. That's on either the intake or exhaust side, and almost never when both are done.

Techs are just wrong often. They don't have to be wrong but lazy causes them to be wrong. If they only follow the diag procedure in the manual, they would be correct about 99% of the time but their paychecks would be much lower.

When they claim warranty repairs, they have to return the bad parts to JAG for evaluation. They didn't mention to you that the O2 sensors are still within warranty on your car, CATs were only 8 years. They were throwing O2 sensors in until they started getting charged back for the labor part of the warranty claims. No impact to customer, but the techs did not appreciate paycheck reductions each the OEM found the returned sensors were actually still good. You were told yours were good, but did they show you how they determined this? lmfao.

I found my Stop/Start System stopped working. It was disabled due to Air/Fuel ratio adaptations out of range. That was the LTFT issues. I'll bet yours has the same condition. I knew I was on the right track when that symptom cleared.

Here's my list of items which can cause this code. This same list allowed to dwell can cause the CAT to actually be destroyed.
CAT physical impact
Exhaust leak
Engine Oil level, if too high it will cause CAT Pollution, easy to clean it up
B1S2-O2, B2
B1S3-O2, B2
MAF B1 & B2
Atmospheric Temperature sens
Atmospheric Pressure sens
High Speed CAN bus errors
Coolant Temp B1 sens Coolant Temp B2 sens
Fuel Pressure High B1 Fuel Pressure High B2 Fuel Tank Pumps, controller, & Sensors
Ignition Misfires
Spark Plugs, Boots, Coils
Knock sensors retard ign operations
Fuel Injectors performance
Long Term Fuel Trim B1 Long Term Fuel Trim B2
Vacuum Leaks
Cam advance adaptations vary
Manifold Pressure sensors
Intake Valve Carbon

Here's my quickest to find the cause order.
If it's safe and running fine, measure 0-60mph should be <<3.8s
-If acceleration is good, internal CAT failure is very unlikely
Use water misting spray bottle to check for vacuum leaks and bad spark plug boots on engine at idle
Reverse shop-vac to blow into tailpipes, plug 3 of 4, use soapy water sprayer to check from O2S3 forward to flange at engine manifold, or smoke instead
Record coolant temp time to dash gauge center from cold start
IF you have access to a nice scanner, get baseline data, find when DTC resets occurred
-Record Start/Stop failure causes
-Record time each bank reaches Closed Loop operation
-Record misfires by cylinder if >2 after hard acceleration
-Record LTFTs, min, max, avg, 0 is the goal but at 61k miles +6% is more likely
-Record STFTs, min, max, should avg near 0, B1 to B2 should vary be conditions similarly
-Record especially O2 sensors S2 and S3 in each bank. S3 should react much slower than S2.
--pump foot brake pedal to cause vacuum leak, check responses of all FT and O2 sensors above, also check they recover correctly when you stop pumping brake.

If cause is still not known, verify each system previously listed.

 

Was the car tuned or otherwise modified? Are the downpipes original?

There's no real way that you have only performance codes on both cats and nothing else if you have mechanical issues. I'd guess the car was tuned and then flashed back to stock, and is now setting the codes for the lack of cats. I've seen this happen many times.

Also, are the fuel trims high all the time, at idle/cruise, etc? If there's a small enough leak to generate excessive fuel trims but not fuel trim codes, it actually won't damage anything, as that's the reason for the fuel trims, the car is catching it and correcting for it. 15% is above what I would like to see but not really out of range depending on fuel quality/ethanol content.

 

Thank you so much for getting back to me and sharing your experience. I had a suspicion that the issue is beyond just CAT failure. Furthermore the dealer told me that my LTFT’s are high due to CAT failure which made no sense.



You are correct on the Auto Start/Stop – when I first purchased the vehicle that was disabled and then when I bought a new battery and reset the vehicle it came back online. The dealer also never showed me how they determined that the O2 sensors are functioning correctly with no issues. They claimed they would cover replacing B1 & B2 S2 & S 3 if I move forward with the CAT replacement. When I did a pre-purchase inspection the technician was suspicious of a Vacuum Leak at the Vacuum Pump but I was making the purchase from out of state and didn’t have the time to diagnose it, When I asked Jaguar to diagnose it they claimed there are no vacuum leaks.



So far I am not seeing any performance issues and the car seems to drive totally fine, I haven’t timed my 0-60 yet but I am excited to do it. That being said; do you think I should be pushing back on Jaguar to re-diagnose the vehicle? I am at a beginner DIY level with no access to a lift so I think I can perform additional OBD reads and visual inspections but will likely need access to a shop if I have to diagnose it further.

• If you were in my shoes were would you start?
• If it ends up being the CATS – have you had any experience with Davico rebuilding the CATS in lieu of ordering new ?

Thank you so much for your help. This is great information !

 

I don’t believe the car was ever tuned and the downpipes are original. I have driven the vehicle for almost 1300 miles (reset the DTC’s a couple of times) and still no codes other than the CAT efficiency codes. I am going to check again but I feel like the Fuel Trims are higher on Idle than Cruise. I only run 93 Octane and have used a Techron Treatment and a Liqui Molly Catalyst Cleaner once.

 

If the LTFT is higher at idle but lower as RPMS increase, it's indicative of an air leak, yes. I have seen cracked valve covers, PCV faults, all manners of places for them to leak. At this point I'd suggest a smoke test of the intake system if there is nothing readily apparent.

It is possible your cats are failing, the car looks at the pre and post cat O2 for an expected change to diagnose for that fault code, so if you are able to log the values of all 4 sensors and watch them change, you can often spot a slow responding sensor or other issue that way. At this age it would not be unlikely that the O2s have deteriorated and could use replacement, but I don't like to just throw parts at a car without knowing why. I would 100% want to investigate the source of the fuel trims before putting very expensive catalysts in the car. Are you sure there are no other codes in it? Did you get a readout via SDD?

 

I had a P0420 on my 2018 R at 36k miles and the dealer replaced it under the 8 year emissions warranty. No CEL since. The pops and bangs with the original factory tune destroy the cats. In your case I would just go with the VAP sport cats at around $1300.

 

His 2016 is out of emissions warranty coverage by this point though. I do agree that it's totally possible for them to degrade with normal 'spirited' driving. We have a campaign on the L494 SVR rovers to update the PCM tune to reduce the degradation of the catalysts over time.

 

Yeah you can have the dealer update the tune to reduce the pops and bangs but personally I enjoy the sound so I told them not to touch it. He could also find a used set but it's hard to know how much life those have left in them.

 

Yes I am sure there are no other codes which is why I am scratching my head. I had Jag do a read out using SDD and they confirmed no other codes as well and that's why they defaulted to failed cats. I just want to make sure that is the case before I spend the money on the Cats

 

I really don't want to lose the tune but I guess I am willing to live with it if it solves the problem

 

My mind was going there too especially because they are about to drop their Black Friday sale but I wanted to treat any unresolved issue first and avoid going the sports cats route since I have an extended warranty

 

Solved - after some extensive diagnostic work the issue was found to be the catalytic convertors. Long story short, the local JLR dealer replaced both CC's (had to wait 3 weeks for shipping from UK) and all 6 oxygen sensors. The O2 sensors were covered under 10 year JLR warranty, and the CC's were covered via a federal 'specific emissions warranty' whereby the manufacturer (Jaguar in this case) has to cover CC's for 8 years or 80,000 miles. Upshot being I paid nothing out of what would have been a $9,200 bill.