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2Addicts | BMW 2-Series forum Technical Topics N55 (M235i) Engine, Transmission, Exhaust, Tuning Jb4 CEL with catless DP

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      04-11-2021, 12:11 PM   #1
GarrettM235i
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Jb4 CEL with catless DP

I installed a mini cat from turner Motorsport on the secondary o2 in order to eliminate the CEL. Now I'm getting a new series of codes. I initially thought that the jb4 eliminated the CEL when installed. I'm running map 2. Looking for options to fix this. Is it possible that the sensor is too far out of the exhaust stream now? Or can this be fixed with tuning?
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      04-11-2021, 03:27 PM   #2
jb-slow
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You don't need a mini cat on there, the jb4 should hide the code on its own.
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      04-11-2021, 05:18 PM   #3
GarrettM235i
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Quote:
Originally Posted by jb-slow View Post
You don't need a mini cat on there, the jb4 should hide the code on its own.
I though it would as well but it didn't. Tunes and everything work fine but still getting cel with jb4.
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      04-12-2021, 08:45 AM   #4
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Quote:
Originally Posted by jb-slow View Post
You don't need a mini cat on there, the jb4 should hide the code on its own.
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Originally Posted by GarrettM235i View Post
I though it would as well but it didn't. Tunes and everything work fine but still getting cel with jb4.
the Jb4 does not suppress any codes for US customers, the downpipe feature only works for international customers
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      04-12-2021, 07:53 PM   #5
GarrettM235i
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Quote:
Originally Posted by mike@x-ph.com View Post
Quote:
Originally Posted by jb-slow View Post
You don't need a mini cat on there, the jb4 should hide the code on its own.
Quote:
Originally Posted by GarrettM235i View Post
I though it would as well but it didn't. Tunes and everything work fine but still getting cel with jb4.
the Jb4 does not suppress any codes for US customers, the downpipe feature only works for international customers
Ahhh. I did not know this. Interesting....
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      04-13-2021, 06:54 AM   #6
jb-slow
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It worked great in my 135, maybe the 2 series is smarter? Either way the best route to fix it is a real tune instead of a piggyback
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      04-13-2021, 10:54 AM   #7
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You can't run those spacers to get away from the CEL. Car won't read the AFR correctly and will cause issues.
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      04-13-2021, 02:38 PM   #8
jb-slow
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The afr is based on the upstream o2. It's the downstream o2 that monitors catalyst efficiency that sets the cat codes. The spacer goes on the downstream just like he has it. I think the issue is the car is smarter than the old school jb4
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      04-13-2021, 02:39 PM   #9
jb-slow
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Just a thought... Are the sensors plugged into the right connectors? Is it possible they got switched?

The more I look at the codes the more I think they got switched
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      04-14-2021, 11:16 AM   #10
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All "newer" updated JB4 software made it so it could no longer auto suppress the CEL from catless setups. As said before, US customers do not have that option available.

You guys should read up on JB4's and stuff on n54tech forum. That place is like the holy grail of all JB4 info you could ever want.

current ECU tunes/tuners (MDH/BM3) do not suffer from this issue as this is coded into the tune and no cel's are illuminated. This does not mean your car will pass smog or anything of that nature, only it will not trigger the light on a constant basis.
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      07-16-2023, 02:01 PM   #11
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Sorry to dig in this old post. I ordered my ER catless downpipe and it should get here soon. I don’t live in the states but I do have a Jb4 installed on my car. Does that mean I can auto suppress my eventual CEL using jb4?
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