Possible $5 fix for post-cat error codes on catless cars

Red_Tears · 12-06-2019, 02:28 PM

I was doing some research today, in preparation to change dp's on my car (within the next month or so, would be sooner but I'm in the final stages of planning and paying for a wedding) and was reading about taking care of CELs since I am going the catless route [insert catted vs. catless argument here] Found a bunch of scary (to me) re-wiring articles to trick the ecu electronically. Then I found this post on bimmerforums by user BMWjiggaB:

https://www.bimmerforums.com/forum/s...DIY-56k-no-way

Basically, you put a spark plug non-fouler into the o2 sensor bung, which pulls the o2 sensor out of the exhaust stream, and all the ecu does when checking the two is ensure pre and post cat have different readings. Since the sensor is no longer directly in the exhaust stream, the reading it returns is different. Now it is entirely possible that in the 20+ years since E36 has been on the road, sensors have become much more sensitive, and this modification may not work for our cars, but for $5 and no real drawbacks, I am going to give it a try.

I have no way to test this yet, but once I get my dp's I will be giving this "mod" a shot. As I am quite uncomfortable modifying the electronics in the ways described by users going the electronic emulation route. (just my 2 cents)

I will update this post with my findings, if others have not by the time I complete the modification.

All credit to user BMWjiggaB: on bimmerforums.

Thanks for reading.

-R

opjose · 12-06-2019, 05:20 PM

Quote:

Originally Posted by Red_Tears

I was doing some research today, in preparation to change dp's on my car (within the next month or so, would be sooner but I'm in the final stages of planning and paying for a wedding) and was reading about taking care of CELs since I am going the catless route [insert catted vs. catless argument here] Found a bunch of scary (to me) re-wiring articles to trick the ecu electronically. Then I found this post on bimmerforums by user BMWjiggaB:

https://www.bimmerforums.com/forum/s...DIY-56k-no-way

Basically, you put a spark plug non-fouler into the o2 sensor bung, which pulls the o2 sensor out of the exhaust stream, and all the ecu does when checking the two is ensure pre and post cat have different readings. Since the sensor is no longer directly in the exhaust stream, the reading it returns is different. Now it is entirely possible that in the 20+ years since E36 has been on the road, sensors have become much more sensitive, and this modification may not work for our cars, but for $5 and no real drawbacks, I am going to give it a try.

I have no way to test this yet, but once I get my dp's I will be giving this "mod" a shot. As I am quite uncomfortable modifying the electronics in the ways described by users going the electronic emulation route. (just my 2 cents)

I will update this post with my findings, if others have not by the time I complete the modification.

All credit to user BMWjiggaB: on bimmerforums.

Thanks for reading.

-R

Didn't work for me even with hi-flow cats.

There are numerous threads here where people have tried things like this with bad to poor results.

Search for O2 sensor extenders here for relevant threads.

bluesy_cube · 12-11-2019, 01:01 PM

If you are only worried about the CEL, MHD or JB4 will take care of it as I assume the reason for new DP is for stage 2 tune anyways.
If it is because of the car inspection, extended o2 sensor MIGHT help. There are mixed reviews about using it.

drwillb · 12-11-2019, 06:52 PM

JB4 will no longer clear O2 sensor codes. Actually, since about a year ago. They’re based in California and wanted to be 50 state legit.

MHD will ghost the code so the dash lights don’t come on. However, that wedding might be eating into the car budget. Hence the $5 Hail Mary.

Been there. Feel your pain but the car budget will heal over time.

nissubaru · 12-12-2019, 12:59 PM

A dpfix would honestly be an easier, more foolproof solution than an O2 spacer. This is the ghetto way of doing things, and typically it's only for people whose stock cars are slightly out of emissions spec. Putting the O2 spacer on our cars is not how you would want to get around the emissions, if it even works at all.

12-06-2019, 02:28 PM	#1
Red_Tears New Member 7 Rep 27 Posts Drives: 2008 BMW 335i Join Date: Sep 2019 Location: Central US iTrader: (0)	Possible $5 fix for post-cat error codes on catless cars I was doing some research today, in preparation to change dp's on my car (within the next month or so, would be sooner but I'm in the final stages of planning and paying for a wedding) and was reading about taking care of CELs since I am going the catless route [insert catted vs. catless argument here] Found a bunch of scary (to me) re-wiring articles to trick the ecu electronically. Then I found this post on bimmerforums by user BMWjiggaB: https://www.bimmerforums.com/forum/s...DIY-56k-no-way Basically, you put a spark plug non-fouler into the o2 sensor bung, which pulls the o2 sensor out of the exhaust stream, and all the ecu does when checking the two is ensure pre and post cat have different readings. Since the sensor is no longer directly in the exhaust stream, the reading it returns is different. Now it is entirely possible that in the 20+ years since E36 has been on the road, sensors have become much more sensitive, and this modification may not work for our cars, but for $5 and no real drawbacks, I am going to give it a try. I have no way to test this yet, but once I get my dp's I will be giving this "mod" a shot. As I am quite uncomfortable modifying the electronics in the ways described by users going the electronic emulation route. (just my 2 cents) I will update this post with my findings, if others have not by the time I complete the modification. All credit to user BMWjiggaB: on bimmerforums. Thanks for reading. -R
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12-11-2019, 01:01 PM	#3
bluesy_cube Private 23 Rep 99 Posts Drives: 2015 F22 M235i xDrive Join Date: Aug 2018 Location: Vancouver, BC iTrader: (0)	If you are only worried about the CEL, MHD or JB4 will take care of it as I assume the reason for new DP is for stage 2 tune anyways. If it is because of the car inspection, extended o2 sensor MIGHT help. There are mixed reviews about using it.
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12-11-2019, 06:52 PM	#4
drwillb BMW Fan 289 Rep 838 Posts Drives: e30 M3, e30 M3, e46 M3 Join Date: Aug 2008 Location: northern NJ iTrader: (4)	JB4 will no longer clear O2 sensor codes. Actually, since about a year ago. They’re based in California and wanted to be 50 state legit. MHD will ghost the code so the dash lights don’t come on. However, that wedding might be eating into the car budget. Hence the $5 Hail Mary. Been there. Feel your pain but the car budget will heal over time.
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12-12-2019, 12:59 PM	#5
nissubaru Lieutenant 233 Rep 564 Posts Drives: 09 335i MSport + 1990 300ZX TT Join Date: Jan 2017 Location: Philadelphia iTrader: (0)	A dpfix would honestly be an easier, more foolproof solution than an O2 spacer. This is the ghetto way of doing things, and typically it's only for people whose stock cars are slightly out of emissions spec. Putting the O2 spacer on our cars is not how you would want to get around the emissions, if it even works at all.
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