Downpipe Help

Steakpizza · 07-12-2023, 11:35 PM

Hey guys,

I got a code P0420 for my 2017 M240ix and from what I’m reading I need to replace my downpipe. Never had any downpipe issues so a few questions.

Looking to stay away from OEM/Catted as they’re expensive, but also wanted to see if there’s any options otherwise that would let me pass emissions (I’m in Pa).

Can a high flow Cat not cause a CEL?

I was reading a bit about an O2 sensor I can get. Is that a permanent fix? Would cause no CEL even if I go catless (and can pass emissions with this?).

Any recommendations is appreciate. Just want to fix this issue while being able to pass emissions and not spend an arm and a leg for OEM.

Thank you guys.

n55david · 07-13-2023, 09:19 AM

Quote:

Originally Posted by Steakpizza

Hey guys,

I got a code P0420 for my 2017 M240ix and from what I’m reading I need to replace my downpipe. Never had any downpipe issues so a few questions.

Looking to stay away from OEM/Catted as they’re expensive, but also wanted to see if there’s any options otherwise that would let me pass emissions (I’m in Pa).

Can a high flow Cat not cause a CEL?

I was reading a bit about an O2 sensor I can get. Is that a permanent fix? Would cause no CEL even if I go catless (and can pass emissions with this?).

Any recommendations is appreciate. Just want to fix this issue while being able to pass emissions and not spend an arm and a leg for OEM.

Thank you guys.

Have you tried an 02 sensor first? It's rare for a cat to go bad without another issue causing it to go bad. A sensor on the other hand could go bad etc.

There are only a few catted downpipes that will guarantee no check engine light and they are usually 1000+ usd.. js

kamilbaran · 07-13-2023, 12:47 PM

I am running VRSF catted downpipe (was about 450 for them). No CEL, no unnecessary raspiness, although they are backordered. I ordered them In May and was expecting them to come end of June but they came almost 3 weeks earlier than expected. Great quality DP for the price, if you're willing to wait a bit to get it I would but if its a quick fix you need, I would check back and see if anything else could throw the code. Depending how many miles and if there was aggressive burbles on before that could lead the cat to burn out. (Happened on my focus rs).

Steakpizza · 07-13-2023, 12:50 PM

Thank you much.

OEM cat has been on for 90k miles, mild burble last 30k or so. Just all research is saying that it’s 95% the cat, I’ll probably have the sensors replaced too and try to do that O2 sensor angle thing so it doesn’t cause a CEL.

mike@x-ph.com · 07-24-2023, 12:51 PM

your best bet is to get the active autowerke downpipe, it won't cause the check engine light and is EPA approved.

Its also brand new so you know it will last a long time before needing to be changed.

WolfGTI · 07-26-2023, 06:59 PM

Running the AA catted DP for 3 years in South NJ - passes emissions and no CEL.

mike@x-ph.com · 07-28-2023, 10:29 AM

Quote:

Originally Posted by WolfGTI

Running the AA catted DP for 3 years in South NJ - passes emissions and no CEL.

Nice!

WolfGTI · 01-03-2024, 07:20 PM

Just to update - Today I passed my bi-annual NJ state inspection, no issues. No codes or any other issues. The AA downpipe is worth the piece of mind. No inspection till 2026.

Dantesboyz · 01-06-2024, 11:12 AM

I have the AA DP from XPH and no complaints, oem comparison pic.
Great quality NO CEL, roughly 10k miles on it.
It fits great too.
Also installed a VRSF high flow cat in my buddies b58 540, CEL came on within a few days, but he coded it out. Fitment was also good but it's shaped a little differently than the AA.

mike@x-ph.com · 01-06-2024, 01:12 PM

Quote:

Originally Posted by Dantesboyz

I have the AA DP from XPH and no complaints, oem comparison pic.
Great quality NO CEL, roughly 10k miles on it.
It fits great too.

07-12-2023, 11:35 PM	#1
Steakpizza Second Lieutenant 118 Rep 293 Posts Drives: 320i Join Date: May 2018 Location: Philadelphia iTrader: (0)	Downpipe Help Hey guys, I got a code P0420 for my 2017 M240ix and from what I’m reading I need to replace my downpipe. Never had any downpipe issues so a few questions. Looking to stay away from OEM/Catted as they’re expensive, but also wanted to see if there’s any options otherwise that would let me pass emissions (I’m in Pa). Can a high flow Cat not cause a CEL? I was reading a bit about an O2 sensor I can get. Is that a permanent fix? Would cause no CEL even if I go catless (and can pass emissions with this?). Any recommendations is appreciate. Just want to fix this issue while being able to pass emissions and not spend an arm and a leg for OEM. Thank you guys.
	Appreciate 0 Tweet Quote

07-13-2023, 12:47 PM	#3
kamilbaran Private First Class 138 Rep 182 Posts Drives: '18 Yas Marina M3, '17 M240i Join Date: May 2022 Location: Chicago iTrader: (0)	I am running VRSF catted downpipe (was about 450 for them). No CEL, no unnecessary raspiness, although they are backordered. I ordered them In May and was expecting them to come end of June but they came almost 3 weeks earlier than expected. Great quality DP for the price, if you're willing to wait a bit to get it I would but if its a quick fix you need, I would check back and see if anything else could throw the code. Depending how many miles and if there was aggressive burbles on before that could lead the cat to burn out. (Happened on my focus rs).
	Appreciate 0 Quote

07-13-2023, 12:50 PM	#4
Steakpizza Second Lieutenant 118 Rep 293 Posts Drives: 320i Join Date: May 2018 Location: Philadelphia iTrader: (0)	Thank you much. OEM cat has been on for 90k miles, mild burble last 30k or so. Just all research is saying that it’s 95% the cat, I’ll probably have the sensors replaced too and try to do that O2 sensor angle thing so it doesn’t cause a CEL.
	Appreciate 0 Quote

07-24-2023, 12:51 PM	#5
mike@x-ph.com Joint Chiefs of Staff 24199 Rep 190,807 Posts Drives: 07-335/12-328/18-M4/21-M4CP Join Date: Sep 2013 Location: Las Vegas iTrader: (23)	your best bet is to get the active autowerke downpipe, it won't cause the check engine light and is EPA approved. Its also brand new so you know it will last a long time before needing to be changed. __________________ Check out our current sale by clicking on this link! https://x-ph.com/sale/ Phone number 702-494-9435
	Appreciate 1 WolfGTI716.00 Quote

07-26-2023, 06:59 PM	#6
WolfGTI Captain 716 Rep 913 Posts Drives: '17 F22,15 E84 M Sport,02 R53 Join Date: Jul 2007 Location: South NJ iTrader: (0) Garage List 2017 BMW M240i [0.00] 2002 MINI Cooper S [0.00] 2015 BMW X1 [0.00]	Running the AA catted DP for 3 years in South NJ - passes emissions and no CEL. __________________ Integrated Engineering engine mounts, Dinan CAI, AA catted DP, Remus resonated cat back. Rogue Engineering SSK & transmission mounts, WaveTrac LSD. Ohlins R&T coilovers, Turner monoball thrust arms, F87 LCAs, GC camber plates, Superpro subframe bushings, Megan Racing adj. RCAs, delrin differential bushings. Stoptech BBK 6 piston (f) 4 piston (r).
	Appreciate 1 jLona24029.50 Quote

01-03-2024, 07:20 PM	#8
WolfGTI Captain 716 Rep 913 Posts Drives: '17 F22,15 E84 M Sport,02 R53 Join Date: Jul 2007 Location: South NJ iTrader: (0) Garage List 2017 BMW M240i [0.00] 2002 MINI Cooper S [0.00] 2015 BMW X1 [0.00]	Just to update - Today I passed my bi-annual NJ state inspection, no issues. No codes or any other issues. The AA downpipe is worth the piece of mind. No inspection till 2026. __________________ Integrated Engineering engine mounts, Dinan CAI, AA catted DP, Remus resonated cat back. Rogue Engineering SSK & transmission mounts, WaveTrac LSD. Ohlins R&T coilovers, Turner monoball thrust arms, F87 LCAs, GC camber plates, Superpro subframe bushings, Megan Racing adj. RCAs, delrin differential bushings. Stoptech BBK 6 piston (f) 4 piston (r).
	Appreciate 0 Quote

01-06-2024, 11:12 AM	#9
Dantesboyz recovering e36er 65 Rep 106 Posts Drives: 2017 M240i Xdrive Join Date: Nov 2017 Location: Johnstown OH iTrader: (0) Garage List 2017 ///M240i XDrive [7.25]	I have the AA DP from XPH and no complaints, oem comparison pic. Great quality NO CEL, roughly 10k miles on it. It fits great too. Also installed a VRSF high flow cat in my buddies b58 540, CEL came on within a few days, but he coded it out. Fitment was also good but it's shaped a little differently than the AA. Attached Images __________________ 2017 F22 M240i, Xdrive, M Performance Package Active Autowerke Downpipe, Dinan Carbon Fiber Intake, Dinan Carbon Fiber Turbo Inlet, Dinan Mid-pipe, xHP Flashtool, MHD Stage 2 To do next list- #1- Wheel Spacers & Tires, #2- B58 TU Pump, #3- Flex Fuel Kit
	Appreciate 0 Quote