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Discussion Starter · #1 ·
2004 M3

Stupid mechanic didn't mark them before installing the headers, how can I be sure which ones are the pre/post cat O2's?
 

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Discussion Starter · #3 ·
I think the retard pulled them all off at the connector. So what I'm asking is where they originate on the car, as in the exact positions or a diagram of where they plug into the wiring harness at.
 

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Upstream o2 sensor is before the cat,the downstream o2 is the second one. Bank 1 is always the side with the # 1 cylinder. Bank 2 is cylinder # 2.
 

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Discussion Starter · #6 · (Edited)
He didn't cut the wires, however he didn't mark the original positions of the O2's before putting the headers on as in he had no clue which O2 was which. I'm not sure if he removed them from the wiring connector or not, but I believe he did to make them reach where the O2 screws into the header. I used the Shark injector afterwards to get rid of the SES light from the rear O2's not being present, the SES light came on about 10 minutes after driving the car around. Just imagine I had 4 O2's hanging under my hood that had the same length of wire to them, how do I figure out which one is the precat for the front bank and the precat for the 2nd bank. Assuming 1st bank is the 3 cylinders nearest the front end of the car.

Edit: i realize they are every other cylinder now that I think about it, so the 1,3,5 cylinders are the 1st bank. "I'm assuming"
 

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Discussion Starter · #7 ·
Also, I'm never taking the car back to them, it's a long story as to why I let them work on it this time and they charged me $1000 to put on a CAI and the headers, that included all the fab work to make the cheap headers actually fit the car.
 

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Bank 1 is cylinders 1,2,3
Bank 2 is cylinders 4,5,6

http://www.bmw-planet.com/diagrams/release/en/e46/index.htm
Complete Vehicle / Drive / Engine Management ..... MSS54 / Digital Motor Electronics / Sensors / Oxygen Sensors -


Test the wires from the O2 sensor connectors to the DME-
Pre cat bank 1 - pin 2 to DME pin 1, pin 3 to DME pin 5, pin 4 to DME pin 14
Pre cat bank 2 - pin 2 to DME pin 13, pin 3 to DME pin 5, pin 4 to DME pin 15

Post cat bank 1 - pin 2 to DME pin 7, pin 3 to DME pin 5, pin 4 to DME pin 16
Post cat bank 2 - pin 2 to DME pin 19, pin 3 to DME pin 5, pin 4 to DME pin 18
 

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Discussion Starter · #9 ·
Here is what I was looking for, it took some searching after writing down all the part #'s.


For those just using the pre-cat O2 sensors because of header install.

Front bank pre-cat, this will be written on the actual O2 sensor.
1743994-04
Bosch part # "not engraved on the O2" 13949

Rear bank, pre-cat:
1405324-04
Bosch part # 13952

For a header install you will have to lengthen the O2 wires to reach where they have been relocated. So if you have an idiot install your headers like I did and he doesn't mark which ones came from what location on the original exhaust manifolds now you should be able to tell which O2 sensor goes to which bank.
 

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Bank 1 is cylinders 1,2,3
Bank 2 is cylinders 4,5,6

http://www.bmw-planet.com/diagrams/release/en/e46/index.htm
Complete Vehicle / Drive / Engine Management ..... MSS54 / Digital Motor Electronics / Sensors / Oxygen Sensors -


Test the wires from the O2 sensor connectors to the DME-
Pre cat bank 1 - pin 2 to DME pin 1, pin 3 to DME pin 5, pin 4 to DME pin 14
Pre cat bank 2 - pin 2 to DME pin 13, pin 3 to DME pin 5, pin 4 to DME pin 15

Post cat bank 1 - pin 2 to DME pin 7, pin 3 to DME pin 5, pin 4 to DME pin 16
Post cat bank 2 - pin 2 to DME pin 19, pin 3 to DME pin 5, pin 4 to DME pin 18
That's a real response, good info :thumbsup:
 
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