[123Britt]

Purchased the (2) 02 Pre-cat sensors and started with the basics of removing the engine plastic cover. Removed the under engine cover and saw the 2 pre-cat 02 sensors. The access is so tight that it looks like I would need to remove the passenger side tie-rod to even have a chance at removal. I can get the off-set 7/8 split tool installed but just not enough room to apply torque with a 3/8in universal + extension to a breaker bar.

I would be very interested in hearing how to accomplish this on an N54.

I am leaning toward getting a tie rod press tool and lowering the tie rod for better access.

[CornFed]

Remove the steering rack instead. It is only 2 bolts. AR Design has a great DIY for replacing downpipes, and removes the steering rack to get access to the precat O2. Start at 7mins and the vid will walk you through it. GL!

How to install AR Design Downpipes:

[123Britt]

29E1Mixture Control Code Cleared


I was about to give up on the 02 sensor R&R due to lack of good access below the (2) pre-cat sensors. But MDANG is the man


Dropped the steering rack and access was just enough to R&R. The break away torque on the old sensors were easy and the new Bosch sensors came pre-lubed with anti seize. I had cleared all the codes with a BT scan tool prior to the sensor swap but it would come back immediately. Now after the R&R the SES Light is out. Currently at 115k. Old sensors did not look that bad -- dark but not gunky , just a little burnt.

THANKS MDANG! I just wish I knew this little gem prior to R&R of the Thermostat and Water Pump replacement. Access like this would make that job much easier.

[CornFed]

You're welcome! I gotta replace my O2 sensors soon also. After installing my DPs, I've been getting intermittent mixture codes as well. Glad everything worked out. Mod On OP!

[GMWNashville]

I haven't had good luck with O2 sensors causing mixture faults on an n54..it's usually injectors..

[123Britt]

Just drove 100 miles. SES light remains out

[123Britt]

OK - looks like I will need injectors --- I order (6) from Tischer and will look to buying the INPA cable.
.
I have replaced so many things on this car -- really makes me wish for the pre-DI turbo days.

[takrdown]

Did the injectors fix the problem?

[bmwhitman]

Originally Posted by CornFed

Remove the steering rack instead. It is only 2 bolts. AR Design has a great DIY for replacing downpipes, and removes the steering rack to get access to the precat O2. Start at 7mins and the vid will walk you through it. GL!

How to install AR Design Downpipes:

Does this apply to N52 E90 cars too? I plan to do this DIY but was hoping not to get underneath car. I don't mind replacing if it's in the engine area underneath hood. Don't have jacks or access to underneath the car.

[Efthreeoh]

Originally Posted by bmwhitman

Does this apply to N52 E90 cars too? I plan to do this DIY but was hoping not to get underneath car. I don't mind replacing if it's in the engine area underneath hood. Don't have jacks or access to underneath the car.

On the N52 you can get to the Bank 1 and Bank 2 upstream (pre-cat) O2 sensors from under the hood. You need to remove the cabin airfilter housing and the engine cover.