Lambda Probe Problem

[kebsterm4]

I am new to this forum, but have enjoyed reading things especially as it pertains to my M4.

I have a custom tune on my M4 from a tuner using the BM3 software. I have catless downpipes, and continue to receive the CEL of "12B304 lambda probe heating after catalyst activation: line break". How can I determine which specific O2 sensor it actually is without having to purchase both of them?

[TypeDre]

Originally Posted by kebsterm4

I am new to this forum, but have enjoyed reading things especially as it pertains to my M4.

I have a custom tune on my M4 from a tuner using the BM3 software. I have catless downpipes, and continue to receive the CEL of "12B304 lambda probe heating after catalyst activation: line break". How can I determine which specific O2 sensor it actually is without having to purchase both of them?

Did you ever figure out what the problem was on this? I have the same exact CEL but I haven't changed anything. Been running BM3 stg2 for a few thousand miles with no issues until recently.

Thanks!

[phantome46]

I’m really keen to understand this also my light just came on

[Flbmwm3]

I have the same issue and have bm3. I also got the other bank which was the other code listed. They are bank 1 and bank 2 post cat o2 sensors.

I’m trying to figure out if they both went bad at the same time maybe as they appear together.

12b304
And
12b404

[TypeDre]

Originally Posted by Flbmwm3

I have the same issue and have bm3. I also got the other bank which was the other code listed. They are bank 1 and bank 2 post cat o2 sensors.

I’m trying to figure out if they both went bad at the same time maybe as they appear together.

12b304
And
12b404

I fixed mine by installing brand new O2 sensors purchased from FCP Euro.

BMW Oxygen Sensor - Genuine BMW 11787848486
and
BMW Oxygen Sensor - Genuine BMW 11787848487

Reflashed car with stg2 OTS BM3 and CEL went away.

[TRYM3]

I had the same issue definitely need o2 sensors

[f80fan]

12B304 = Bank 1, cyl's 1-3, part 11787848486

12B404 = Bank 2, cyl's 4-6, part 11787848487

https://www.realoem.com/bmw/enUS/sho...88#11787848487