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Hey forum.
I have “2715 DME: oxygen-sensor heater before cat. conv., bank 2: activation”
Firstly, which is the bank 2 sensor, front or back?
Secondly, is that the L=570mm or L=990mm part?
Secondly, any tips how to remove/replace, as it looks tight in there with poor visibility?

I have a sensor replacement tool and intend to buy a Bosch replacement.

Pre cat is the highest sensor. Lots of plus gas on it for a few days before you start.
Buy a lambda socket it will make your life easier.

Thanks. There are two pre-cat sensors, I want to know which one is bank 2.

I have a lambda socket tool, but the access still looks tight.

The front cylinders are Bank1 and the rear ones nearest to the cabin are Bank 2, unless someone corrects me

Cylinders are numbered front (by rad) to back (near cabin). Bank one will be first 3 cylinders (i.e closest to radiator). Bank 2 will be the other 3.

So sensor 1 (pre cat), bank 2 will be 990mm. Best to get and replace both though mate.

This is all assuming you have the M54 engine like me. I replaced mine last week with some much needed help from the forum!

Zedebee wrote: ↑Sun Mar 24, 2024 11:46 pm Thanks. There are two pre-cat sensors, I want to know which one is bank 2.

I have a lambda socket tool, but the access still looks tight.

Again, assuming you have the M54 eninge, there's a heat shield on the left. Remove the two bolts and bend that sucker all the way back. This will give you access the side of the engine, down where the sensor is. This is tight, but I managed it. Just make sure you occasionally twise the sensor wires around as you loose the sensor (obviously unplug them first). I found that if I didn't 'guide' the sensor wires around the the same axis as I loosened them, they'd keep spinning back around.
Not sure that makes sense but you'll figure it out when you start!

Dr. Zed, that’s really helpful thanks. 2.5 Maldives, same as yours .
If you don’t mind me asking what sensors did you go for and where did you get them. BMW are exorbitant, but Bosch seem to be available for about £60 each.

Zedebee wrote: ↑Wed Mar 27, 2024 10:46 am Dr. Zed, that’s really helpful thanks. 2.5 Maldives, same as yours .
If you don’t mind me asking what sensors did you go for and where did you get them. BMW are exorbitant, but Bosch seem to be available for about £60 each.

I got Bosch mate. Got them from APD in Swindon. Think it was 150 for both? Can't really remember as I traded in an old alternator that I needed to hand back as part of their refurb programme.

There's also two or three zip ties at the back of the engine for that sensor but make sure you cut the right ones so you don't have cables flying around unnecessarily.