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///M3 Forum
The BMW E46 ///M3 is the M version E46 and puts out an amazing 333 HP and 262 lb-ft of torque at stock specs! There are an amazing amount of modifications for both the coupe and convertible models so read up and get started modifying your cars today!

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Old 07-02-2013, 10:27 PM   #1
bmwe46nyc
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Headers/o2 sensors question

Hi im a little confused about something. I never had aftermarket headers b4 so I need some help. I purchased my M3 about 2 months ago. Among some other things it came with "black ceramic coated headers". Anyways because of a broken ankle I just started driving it about a month ago. The car is awesome. Drives great and all that. Today I noticed something that I didn't noticed before while wiping down engine compartment. I saw one of the o2 sensor not in place/connected. It was just there just hanging. But it looked like it was tied down and left unhooked on purpose. Theres no check engine light, car runs great but there is one code that comes out in the peake code reader, "Exhaust gas temperature sensor". Is that sensor supposed to be out? Thanks
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Old 07-02-2013, 11:04 PM   #2
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NO ALL THE SENSORS GOTTA BE IN THE HEADERS. In US - M3 models from 01-06 there are four 02 sensors, two front ones PRE-CAT sensors also called as a primary which are first in place and they are b4 the cats. The two others are POST-CAT sensors also called as a secondary sensors and EGT sensor. All the sensor are and have to be in the headers, otherwise the car will throw a lot of the codes and run very bad
I don't know what you have done to ur car along with headers, but if you did some tune for no cat's you don't have to worry for the POST-cat sensors.

There is also EGT sensor and that's ur problem. You need to place that sensor in the headers and clear your codes you should be fine if the sensor is not damaged.
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Old 07-02-2013, 11:23 PM   #3
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Re: Headers/o2 sensors question

Thats what I thought and thats why i find it so weird how car is running so smooth. The only software upgrade that I was told of was shark injector....

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Old 07-03-2013, 11:06 AM   #4
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If they are the secondary o2's then the headers may be plugged at the bungs and you could have a tune to disable the rears.. What I would do if you're curious, get in touch with the big name tunes for our cars and see if they will check your vin. I did this with my old mk5 gti and found out it was APR stage 2+ tuned. *23lbs of boost on logs = not stock lol* Maybe you got a little surprise!

But I still feel even with them disabled and plugged in just hanging there would present some sort of issues..
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Old 07-03-2013, 11:38 AM   #5
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Thats what I thought and thats why i find it so weird how car is running so smooth. The only software upgrade that I was told of was shark injector....

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The Shark Injector for headers I believe disables the Post Cat Sensors.

http://www.turnermotorsport.com/p-15...s-no-cats.aspx

So as above, they probably capped the header bungs, and just left the sensors hanging.
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Old 07-03-2013, 12:31 PM   #6
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So could one just unplug it completely and be okay? Much better than leaving them hanging..
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Old 07-03-2013, 01:41 PM   #7
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So could one just unplug it completely and be okay? Much better than leaving them hanging..
That I'm not sure about. Im sure they have some juice going to them. Don't think the shark completely disables them like other tuners.

"The secret to the Shark Injector Race software is that it 'turns down' the readings from the rear O2 sensors to eliminate codes for 'cat-inefficiency'. The DME will then rely on the front pair of O2 sensors and the stock EGT sensor only."

You can try. If you get a code, just plug em back in, and tuck them away.
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Old 07-03-2013, 01:49 PM   #8
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Hmm interesting, I'm going with evolve when I get a tune, will have them completely turned off then. Thanks for the info!
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Old 07-03-2013, 02:49 PM   #9
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Headers/o2 sensors question

Quote:
Originally Posted by Mf3st View Post
NO ALL THE SENSORS GOTTA BE IN THE HEADERS. In US - M3 models from 01-06 there are four 02 sensors, two front ones PRE-CAT sensors also called as a primary which are first in place and they are b4 the cats. The two others are POST-CAT sensors also called as a secondary sensors and EGT sensor. All the sensor are and have to be in the headers, otherwise the car will throw a lot of the codes and run very bad
I don't know what you have done to ur car along with headers, but if you did some tune for no cat's you don't have to worry for the POST-cat sensors.

There is also EGT sensor and that's ur problem. You need to place that sensor in the headers and clear your codes you should be fine if the sensor is not damaged.
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Old 07-03-2013, 04:44 PM   #10
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Post cat sensors can be turned off from ECU safely...
Primarys' and EGT are a must.
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Old 07-04-2013, 12:13 AM   #11
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Re: Headers/o2 sensors question

Im heading to mechanic next week to find out if headers bungs are capped. Ill keep ya posted. Thanks for info

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