E46 M3 Bosch Oxygen Sensor guide

[Phoenix///M3]

I found this incredibly useful when doing headers

https://drive.google.com/file/d/1AP7wcykYWjHvsiEKWOzWEMddagd_kbSb/view?usp=sharing

[gixxer]

I must have been a real doofus to use the OE sensors all these times.

BOSCH, maker of the OE sensors, their prices, are these legit prices (from ECS Tuning).

Usual BMW markup's over their BOSCH OE supplier's same parts?

Urgh.......

BOSCH part numbers below are just as good, if not same as BMW's own, right? (yes, stupid question)

[Tbonem3]

You're gonna feel like an even bigger doofus when you find out that the actual sensor (not the harness/plug) is only $20, and you can splice a new one in using the existing cable harness which is the "special part" that allows them to charge $100+ ea.

[cornerbalanced]

For those with catless headers, only sensors that matter are pre-cat cyl. 1-6 correct?

[sapote]

Do all S54 years use wideband sensor or only the later cars?

[heinzboehmer]

Do all S54 years use wideband sensor or only the later cars?

Only Z4M has widebands. All other S54 cars have narrowbands.

[Thoglan]

You're gonna feel like an even bigger doofus when you find out that the actual sensor (not the harness/plug) is only $20, and you can splice a new one in using the existing cable harness which is the "special part" that allows them to charge $100+ ea.

Do you have a part number for just the sensor?

[Obioban]

Something I noticed after ordering the wrong sensors a couple of times-- the realoem PNs for pre cat 02 sensors on the CSL diagrams are wrong.

[elbert]

I must have been a real doofus to use the OE sensors all these times.

BOSCH, maker of the OE sensors, their prices, are these legit prices (from ECS Tuning).

Better yet, go to Rockauto. The same Bosch precat sensors are $89 and $56

https://www.rockauto.com/en/moreinfo.php?pk=502127&cc=1422302&pt=5132

https://www.rockauto.com/en/moreinfo.php?pk=501765&cc=1422302&pt=5132

[Tbonem3]

For those with catless headers, only sensors that matter are pre-cat cyl. 1-6 correct?

"matter" depends on interpretation, but if you mean performance, yes - Precat bank 1 (1-3) & bank 2 (4-6)

Do you have a part number for just the sensor?

I tried to find my previous order on ebay/amazon, and couldn't. You can search for "4 wire bosche oxygen sensor" Was $20, probably is more now post covid/inflation.

[PSUEng]

I pulled the Bosch P/Ns from their website and ordered from Autozone with an extra 20% off--best prices I found at the time. Running them now, and they work perfectly fine.

[gixxer]

Better yet, go to Rockauto. The same Bosch precat sensors are $89 and $56

https://www.rockauto.com/en/moreinfo...422302&pt=5132
https://www.rockauto.com/en/moreinfo...422302&pt=5132

Bank1 oxygen sensor picture on their web site looks "normal".

But the picture on their web site for the bank 2 looks odd at the sensor tip? Maybe the picture is not accurate (???).

[gixxer]

BTW, not to digress off from main topic, the car is 2004 and has 29,002 miles on it. Recently been getting the D6 and D7 fault codes, for slow responding pre-cat sensors on "both" banks.

Interestingly about ~3,500 miles earlier i had both of these sensors replaced (with BOSCH OE parts).

The car is modified with supercharger, meth, nitrous, SS stepped headers, race cats, etc. with custom tunes for E85.

Maybe my tune is eating up these sensors?

I'm reading that the stock original sensors are "supposed to" last for ~100K miles before needing replacement, on a "stock" car.

[Tbonem3]

Maybe too lean/hot? You have a local dyno or maybe install a wideband in secondary bung to monitor afr.

[gixxer]

Maybe too lean/hot? You have a local dyno or maybe install a wideband in secondary bung to monitor afr.

Yes, i do have wideband sensors on both banks, and tied to individual AFR gauges.

From recent dyno sessions, the car on dyno was not showing sign of lean to suggest too much hot air.

But i will bring this up with the tuner in next visit.

The sort of rule of thumb i'm going by, according to my tuner is, at the WOT,

11-12 is the goal
13.5 to 16.5 good
>16.5 = lean
<12.5 = rich
19, 20, 22 too lean (not enough fuel)