[Skyhigh]

There are things you could do.
First I would scan to see the exact error code. It may give further clues…
A long shot, but a free of charge one.

[aardate]

Unfortunately that's a risk we all take when we start mod'ing our cars. Even using top of the
Line parts or even oem parts can sometimes create unwanted issues.

As long as the car is driving fine then you are ok I guess. Please keep us updated on what you find.

[BMWILUVU]

Is it really unexpected though because the disclaimer was there?
"When installing the Akrapovič downpipe, remapping the ECU is mandatory in order to prevent potential “check engine light” warning signals." I still am surprised an HJS-400 which is EC compliant would throw a CEL even though there are difference between the Euro block specs and ours. Are we sure there is an HJS-400 in there for sure?

[Skyhigh]

Originally Posted by BMWILUVU

Is it really unexpected though because the disclaimer was there?
"When installing the Akrapovič downpipe, remapping the ECU is mandatory in order to prevent potential "check engine light" warning signals." I still am surprised an HJS-400 which is EC compliant would throw a CEL even though there are difference between the Euro block specs and ours. Are we sure there is an HJS-400 in there for sure?

Have you read any of the posts in this thread so far……?
I suggest you do. Will find answers there.

[Hein Jockins]

Originally Posted by Skyhigh

There are things you could do.
First I would scan to see the exact error code. It may give further clues…
A long shot, but a free of charge one.

It's a cat efficiency error: "Efficiency too low." (#18000) if the cat was clogged or faulty in any way, I would get any other fault besides this one. Not to mention the DP was just removed and inspected to insure this isn't the case. So this error is basically what would happen if you install a high flow cat which is what I did. Maybe this is just normal..

[Skyhigh]

I don't know how much you want to dig into this, but why don't you drop a line to HJS and ask what the explanation for both your situation and the warning on Akrapovic's website could be…!?
The installed and correspondingly placarded cat is in reality their product. And they claim it is Euro 6 compliant.

[Hein Jockins]

Good idea-- I Just sent them an email, and I'll update when I hear back.

[dmanb2b]

Originally Posted by Hein Jockins

It's a cat efficiency error: "Efficiency too low." (#18000) if the cat was clogged or faulty in any way, I would get any other fault besides this one. Not to mention the DP was just removed and inspected to insure this isn't the case. So this error is basically what would happen if you install a high flow cat which is what I did. Maybe this is just normal..

If this were a lower cost 200 CEL catted DP, I would agree it could be normal. A $2K catted DP with what is supposed to be one of the best, if not the best aftermarket cat, unacceptable IMO, but they did disclose it as a possibility.

TBH your best option here is to just get an aftermarket tune and turn off cat monitoring. I understand you wanting to keep warranty, but the warranty is already toast unless you convert it back to stock before service. Also, with the CEL on, you won't know if any other issues happen to pop up that would trigger a CEL but no limp mode.

[Hein Jockins]

Originally Posted by dmanb2b

If this were a lower cost 200 CEL catted DP, I would agree it could be normal. A $2K catted DP with what is supposed to be one of the best, if not the best aftermarket cat, unacceptable IMO, but they did disclose it as a possibility.

TBH your best option here is to just get an aftermarket tune and turn off cat monitoring. I understand you wanting to keep warranty, but the warranty is already toast unless you convert it back to stock before service. Also, with the CEL on, you won't know if any other issues happen to pop up that would trigger a CEL but no limp mode.

What's confusing me is the fault clears itself for a 2-5 days, then returns for a day or 2. So at some point, the ECU is saying, "everything looks good here." Not sure if this helps me isolate an issue or not..

The store I bought it from states this: "It incorporates a sporty catalytic converter - which is type-approved to meet ECE regulations, making the whole system ECE compliant - and so no remapping is needed for this performance upgrade."

I haven't heard from HJS yet, so I emailed this distributor not blatantly asking for a replacement, but having a discussion as to why this happens. I mentioned I'm confused why I get CEL when both the cat and this store's website markets this DP as emissions compliant. Their response: "I don't fully understand the science behind it, but I do know that anytime you alter the OEM cats, there's a risk the ECU can reject it."

I'm going to pursue a replacement from them, but currently crafting a response cause I'm not expecting to get a replacement.

[dmanb2b]

Originally Posted by Hein Jockins

What's confusing me is the fault clears itself for a 2-5 days, then returns for a day or 2. So at some point, the ECU is saying, "everything looks good here." Not sure if this helps me isolate an issue or not..

The store I bought it from states this: "It incorporates a sporty catalytic converter - which is type-approved to meet ECE regulations, making the whole system ECE compliant - and so no remapping is needed for this performance upgrade."

I haven't heard from HJS yet, so I emailed this distributor not blatantly asking for a replacement, but having a discussion as to why this happens. I mentioned I'm confused why I get CEL when both the cat and this store's website markets this DP as emissions compliant. Their response: "I don't fully understand the science behind it, but I do know that anytime you alter the OEM cats, there's a risk the ECU can reject it."

I'm going to pursue a replacement from them, but currently crafting a response cause I'm not expecting to get a replacement.

I wish you best of luck and I hope they do the right thing. Sometimes cats are just bad...it's happened with AA pipes, but they have always stood behind the product. I hope the distributor does the same, given the claim

[Hein Jockins]

Thanks, man. Is there any truth to the ECU rejecting some cats that aren't OEM? I've never heard this, but I'm no expert. I kinda feel like this is the line that gets thrown out to negate liability when you have a problem after modifying a car.

[dmanb2b]

Originally Posted by Hein Jockins

Thanks, man. Is there any truth to the ECU rejecting some cats that aren't OEM? I've never heard this, but I'm no expert. I kinda feel like this is the line that gets thrown out to negate liability when you have a problem after modifying a car.

You are welcome! No, that's a line of BS. Either the cat is efficient enough to keep the o2 sensor from triggering a fault or it isn't. There are plenty of us running aftermarket cats and no-fault. However, even new cats can be bad and this just may be one of those cases OR the shop is not catching a bad o2 sensor, connection, etc.

[Skyhigh]

Originally Posted by Hein Jockins

What's confusing me is the fault clears itself for a 2-5 days, then returns for a day or 2. So at some point, the ECU is saying, "everything looks good here." Not sure if this helps me isolate an issue or not..

That's very typical, actually. In the family there is a catless car, which, to avoid CEL, has an O2 spacer installed to take the O2 sensor away enough from the exhaust gases to fool it that it's all good. Except that it does not work that well - every few months the CEL comes... and after a few weeks disappears. Meaning the values the sensor measures are borderline and only occasionally go beyond the threshold.

[Hein Jockins]

Originally Posted by Skyhigh

That's very typical, actually. In the family there is a catless car, which, to avoid CEL, has an O2 spacer installed to take the O2 sensor away enough from the exhaust gases to fool it that it's all good. Except that it does not work that well - every few months the CEL comes... and after a few weeks disappears. Meaning the values the sensor measures are borderline and only occasionally go beyond the threshold.

Even without spacers this is typical?

[Skyhigh]

Without a spacer the CEL would be on all the time! But remember - I am talking about a car without ANY cat.
Yours is with a cat, but apparently not efficient enough, for whatever reason. Which has the same result as inefficiently fooling the sensor with a spacer - borderline values.

That seems to be the most likely hypothesis, assuming they inspected the installation thoroughly and found nothing obvious (such as the exhaust sucking air from somewhere, badly installed sensors, sensor wiring issue or faulty rear sensor (now excluded, since replaced).

[Hein Jockins]

Right--this is what leads me to believe it's actually an issue with the cat and not the ECU "rejecting" it. Only way to know would be to get a replacement, which I'm still waiting to hear back.

[Skyhigh]

That looks more and more likely, yes.

[Hein Jockins]

From HJS: "Akrapovic sources a wide range of different HJS catalytic converters. The selection of the catalytic converters and their use is the responsibility of our partners. Please contact Akrapovic directly."

To note, my question to them was simply asking if they could shed any light on how it's possible to get a cat efficiency fault with an emissions compliant cat. So this response wasn't them deflecting some sort of demand or request I had. I sent him the specs on the downpipe and the cat with my initial question, so he should be aware of which specific cat I'm referring to.

Anyways, this is still open-ended, but hopefully I'm the only one who cares. I'm awaiting to see if the company I bought this from will give me a replacement. Other than that, still not sure if mine is a dud or if not all cats and/or ECUs are made equal.

[Skyhigh]

Very disappointed from both Akrapovic's and HJS customer support and responses in this case! 👎🏼👎🏼 Very unexpected behaviour.

Which ModelYear is your car again?

[Hein Jockins]

Originally Posted by Skyhigh

Very disappointed from both Akrapovic's and HJS customer support and responses in this case! 👎🏼👎🏼 Very unexpected behaviour.

Which ModelYear is your car again?

Agreed. Which is why I mentioned I wrote them asking if and how it would be possible to get CEL..not demanding free shit. You would think someone in the supply chain of this Downpipe would know lol. So I'm still left wondering if this is normal or it's a faulty cat.

It's a 2017 340.

[Skyhigh]

Given that you are still the only person (I know of) with this issue with not just Akrapovic, but any other HJS cat…. I am forced to believe you simply got a bad one. Initially I was rather putting my money on a faulty installation or sensor, but apparently that's unlikely now.

I am a member of several German groups and forums. So many people driving those (and registering them formally on the vehicle, passing emissions every year or every second year)…. You would think there would be other cases like this.

[Hein Jockins]

Originally Posted by Skyhigh

Given that you are still the only person (I know of) with this issue with not just Akrapovic, but any other HJS cat…. I am forced to believe you simply got a bad one. Initially I was rather putting my money on a faulty installation or sensor, but apparently that's unlikely now.

I am a member of several German groups and forums. So many people driving those (and registering them formally on the vehicle, passing emissions every year or every second year)…. You would think there would be other cases like this.

Yeah I'd say that's what's most likely. Was kinda surprised I continued to have this issue after the o2 sensor replacement, but that in addition to the cel only showing a fault every once in a while makes me think it's just a dud cat.

Currently in talks with whom I bought this from about getting a replacement. But I have a feeling they're gonna to say "well yes we say on our site this is emissions compliant and is great for someone who wants to pass emissions…but akrapovic says you might have to remap the ecu so sorry not our fault"