imalabil, what heizervr6 showing here is replacing POST cat O2 sensors, not precat. Yes we should change precat O2 sensor at 100K services, however, the postcat can be replaced later (after 120K miles or whenever they are faulty). I replaced all 4 of them last week and precat was easy to replace but postcat gave me more difficult to locate and runing the harness. Overall, they are not a bad job.

Precat sensors mounted on the size next to spark plugs harness. You can see them without open the engine cover.
Postcat sensors mounted on intake manifold and you have to remove right side engine cover to disconnect/plug them.

Dealer sold O2 sensors exactly the same as the sensors in the link above, just double price.

About tranny fluid, i came to my local dealer, tech person at dealer told me i should NOT change tranny fluid, it's life time and nearly 60-70% BMW owners come back for tranny services after they change fluid. So i ignore tranny fluid for now except I have to.

I opened the hood and clearly saw the pre-cat sensors sitting there on the exhaust manifold. My new Bosch 13477 sensor should arrive in a few days. I might pull the washer tank to make the sensor closest to the firewall a bit easier to change. I need to replace the rear washer pump anyway.

About "lifetime" trans fill--I bought this vehicle about a year ago and missed all the advertising hype about never having to change the trans fluid. I'll call my dealer today to get his take, but I really have never heard of them turning down service work, especially when my owner's manual says that fluid should be changed at 100K.
I've been reading plenty of previous posts, and it looks like there are opinions on both sides of the issue.

If there is nothing to be gained, I'd rather leave it alone, especially due to the expense of the fluid. I just can't get past the owner's manual recommendation, though.

Bill

Bosch OEM sensors are $44 each at Amazon, that's where I got mine. The bundled socket I also got, so replacing my sensors (pre-cat) including the special tool was $107 and 30 minutes of my time. Better than $750 at the stealer (not that I'd ever pay that but the average indy charges upwards of $400).

Amazon.com: Bosch 13477 Oxygen Sensor, OE Type Fitment: Automotive

I won't change transmission fluid unless i have to.

Mark, that's cheap!

My indy has been working on BMWs for 20 years. He strongly recommends changing the tranny fluid every 50K miles, based on his experience RE: how long they last with and without doing so.

I trust him on this because we go back years and he's equally adamant about NOT doing other stuff (for example told me to leave the O2 sensors in past 100k despite maintenance schedule because they work fine sometimes up to 150k without throwing a code).

Mark, i understand - some indies who has been working on BMW many years like him also say the same. I don't know how BMW transmission fluid services in the past but in the modern BMW they don't recommend to change the fluid. I have asked dealer tech person why we don't have to change tranny fluid he said sometimes changing fluid the transmission gear and clucth not working good with new tranny oil and create problems [!?]. That's what he said.
On my previous BMW 528i 1999, i drove her for 214K miles without changing transmission fluid and i had no problem with transmission since i purchased her at 21K miles. X5 with 4WD/transfer case, it's more stress and i don't think their transmission got that last long comparing to other series.

Where did you get this software? Is it free?

Yes, software was free with the purchase of the diaghead. Tons of places in China sell them and provide either a CD or download link. :thumbup:

Are there torque specs for installing the downstream oxygen sensors? I am about to do the O2 sensor this weekend.

If the fluid is life time why did they include a drain plug? American trans doesn't have drain plugs, but a fluid change is advisable as part of the maintenance schedule. Seems to me that it would be cheaper to build a transmission pan without a drain plug.