catalyst inefficiency codes, 100% stock

[fragment]

Happened three times now. Going in to dealer tomorrow. Will update ...

 

[blkout]

My 2024 CT5 BW recently threw P4020 code, but only after I installed a JLT intake. I reset the code, removed the JLT intake and the code didn't come back. Reinstalled the JLT intake and the code came back again within a few days. Removed the intake again and reset the code and it hasn't come back since. I've even replaced the right rear O2 sensor thinking maybe it had gone bad, but it didn't change anything either.

My car is going to Vengeance Racing on Dec 1 to have a Magnuson 2650, 103mm throttle body and JLT intake reinstalled, ECM tuned so they will tune it so that the code doesn't come back.

I am curious what's causing yours though if your car is stock. I'm wondering if the 02's are set too sensitive since these cars only have two catalytic converters vs four converters on the ZL1. I've never seen this issue on the ZL1 platform.

 

[fragment]

Dealer has ordered both cats and O2 sensors. I asked if the cats tested bad, and the tech looked at me like i had two heads and said "they tested bad when the light came on". So I guess they're just using the parts cannon and the OBDII logic.

Parts will take about 10 days to arrive. I looked at the cat location and it looks like a bitch of a job.

 

[blkout]

Dealer has ordered both cats and O2 sensors. I asked if the cats tested bad, and the tech looked at me like i had two heads and said "they tested bad when the light came on". So I guess they're just using the parts cannon and the OBDII logic.

Parts will take about 10 days to arrive. I looked at the cat location and it looks like a bitch of a job.

How many miles are on the car? It's really hard to imagine the cats are bad. I think the O2s sensors are setup too aggressive and causing them to throw codes when they shouldn't. A brand new set of cats and O2 sensors may solve the issue for a short period of time but I suspect it will come back again. These cats just aren't that fragile. I understand that the tech has no other answers and it doesn't cost him anything to replace all this under warranty so he's just taking the shotgun approach.

 

[fragment]

Just under 50,000 km

 

[blkout]

Just under 50,000 km

More than I expected but honestly, catalytic converters or O2 sensors should not go bad that quickly unless there was a bad run of cats during some point in the years these cars were manufactured.

 

[TERRAVAST4]

Have you checked for any saved codes for misfires? Was it throwing the code random or possibly after spirited driving?

 

[vagabond]

Folks have had catalytic converter issues on the forum. Especially when WOT a lot. I've had mine replaced. Ask them to check your plugs.

 

[Grinch412]

I currently have 42k on the odometer and I drive my car like I stole it daily. I just got the P4020 and have cleared it multiple times but it keeps returning. I do have the JLT intake but I doubt that has anything to do with a P4020. I will be taking it into the dealer and I am sure they will try O2 and cats.

 

[blkout]

I currently have 42k on the odometer and I drive my car like I stole it daily. I just got the P4020 and have cleared it multiple times but it keeps returning. I do have the JLT intake but I doubt that has anything to do with a P4020. I will be taking it into the dealer and I am sure they will try O2 and cats.

The JLT intake caused P4020 on mine, no matter how many times I reset it, it came back. Once I removed the JLT intake, it stopped. I ended up having my car tuned for the JLT intake and its not an issue anymore. I think the issue is that the MAF can't understand all the additional airflow from the JLT intake, especially since JLT doesn't use an air straightener in the duct. A tune will fix it though.

 

[fragment]

So the dealer replaced both cats and all O2 sensors. They showed me the warranty "invoice" and it was over CAD$11k. They said the tech with 30 years experience did the work (I'm wondering if everyone gets that answer when they ask). So far, no codes and no rattles or new noises from the work.

I agree that the cats were unlikely the cause, but if the fix holds then I "guess" I'm satisfied.

 

[marcmac]

There's a guy in my local chapter in the v-club who's had cats failed and replaced.

 

[blkout]

There's a guy in my local chapter in the v-club who's had cats failed and replaced.

I'm sure that's entirely possible, especially if they track their cars a lot, but I doubt its related to the P4020 code that many people get when installing the JLT intake.

 

[thefleshrocket]

I just got the P0420 code in the last couple hundred miles. Actually, I've had the CEL for a couple hundred miles, just got around to checking it last night. It's bank 1. Car is a stock 2023 with 7900 miles on it. Probably 220-240 minutes of track time, otherwise street driven. I always let it warm up but once warm, I am not shy about running it hard. I have an appointment with the dealer on Tuesday. I'm not happy about having anyone touch my car, but at least it's still under warranty.

 

[blkout]

I just got the P0420 code in the last couple hundred miles. Actually, I've had the CEL for a couple hundred miles, just got around to checking it last night. It's bank 1. Car is a stock 2023 with 7900 miles on it. Probably 220-240 minutes of track time, otherwise street driven. I always let it warm up but once warm, I am not shy about running it hard. I have an appointment with the dealer on Tuesday. I'm not happy about having anyone touch my car, but at least it's still under warranty.

I really think they're false positives. I think these cars have the secondary O2 sensors set WAY too sensitive. The fact that you have track time makes it more likely that it COULD be a cat, but I'm still doubtful.

 

[thefleshrocket]

I really think they're false positives. I think these cars have the secondary O2 sensors set WAY too sensitive. The fact that you have track time makes it more likely that it COULD be a cat, but I'm still doubtful.

You're probably right that it's a false positive, but since the car is under warranty, I'm gonna let the dealer have at it. If it was out of warranty, I would probably add some CAP catted O2 spacers--I have them on my 2011 Audi S4 and my 2004 Porsche 911 Turbo, both of which are decatted, yet don't throw codes because of the magical spacers.

 

[blkout]

You're probably right that it's a false positive, but since the car is under warranty, I'm gonna let the dealer have at it. If it was out of warranty, I would probably add some CAP catted O2 spacers--I have them on my 2011 Audi S4 and my 2004 Porsche 911 Turbo, both of which are decatted, yet don't throw codes because of the magical spacers.

Don't blame you at all since its under warranty. Another option once you're out of warranty is the Soul Performance or Fabspeed high flow cat downpipes. They're not cheap but you won't have to worry about them going bad but from what I hear, the Fabspeed cats have an issue setting a CEL. I heard they're being redesigned from one of their retailers.