[clairvoyant]

One of my after cat O2 sensors throws 2C9E error.
All local independent BMW garages in my hood are all booked all the way until late summer. Before I attempt the impossible with my technically/spatially challenged state.
I read the forum DIY downpipe removal guide and have the following questions:
1. Can we replace the after cat O2 sensors by only removing the engine splash shield without going through the DIY rigmarole process?
2. Once I remove the engine splash shield, is there enough space to squish a wrench to remove/install the O2 sensors?
Thank You

[Tzu]

Assuming your front end is jacked up or on ramps, then yes, easy job.

I use a 7/8" ring spanner wrench with a section cut out of it so it can slip over the O2 sensor. The slight angle of the ring is also handy if you're replacing the narrowband for the front turbo, as that sensor is closer to the top of the side of the pipe, near the transmission. Space is tight, but take your time.

Unclip the sensor, and remove the mid section retaining clip first, it's a little easier that way.

Shouldn't take longer than 15-20 mins.

Cheers.

[clairvoyant]

Yes, I will use ramps.
What does a 7/8" ring spanner wrench look like?
Thank you very much, your instruction is very useful.

Originally Posted by Tzu

Assuming your front end is jacked up or on ramps, then yes, easy job.

I use a 7/8" ring spanner wrench with a section cut out of it so it can slip over the O2 sensor. The slight angle of the ring is also handy if you're replacing the narrowband for the front turbo, as that sensor is closer to the top of the side of the pipe, near the transmission. Space is tight, but take your time.

Unclip the sensor, and remove the mid section retaining clip first, it's a little easier that way.

Shouldn't take longer than 15-20 mins.

Cheers.

[MilehighM3]

A 22mm wrench is the O2 is what size it takes. There are also O2 sensor sockets available that work well for them also.

[ianthegreat]

Which O2 sensor?

There are pre-cat (in your downpipes before the cats) and post cat (further down your exhaust).

A stubby wrench works well if you can't seem to fit.

[Tzu]

He said after cat, meaning the narrowbands closer to the midpipes.

OP, a ring spanner is the ring side of a typical wrench. The other side is open. I didn't want to buy an O2 tool so I just cut a slot in an old 7/8" wrench. 22mm also sounds right.

Your'e over thinking it. Just go do it, you'll figure it out pretty easy.

[Brey335i]

You should be able to do it without removing the downpipes with the right tools. They unclip easily once you have removed them from the downpipes. I also use a 7/8" wrench.

[ECSTuning]

As stated lifting the front of the car should give you enough access to remove the o2 sensor. A wrench like the Schwaben 7/8" Flexible Oxygen Sensor Wrench makes the job a lot easier.

[CarbonDuc27]

I am in the same boat after breaking one of mine during my downpipe install

Problem is I have a real problem getting the wrench/socket in between the downpipes. They are racelands and the location of the rear 02s is a little different i guess.

I am dreading it if I end up having to loosen the DPs at the turbos.

[ECSTuning]

^ouch! I've seen a few cases where the downpipes did have to be dropped slightly so remove the o2s. It's not fun but sometimes it's what you have to do!

[ianthegreat]

Yup, I replaced an O2 sensor after a botched DP install once. Never took my car for anyone to work on it again. DIY to ensure quality and peace of mind.

[clairvoyant]

Yes, these are the post cat O2 sensors (the one closer to the midpipes/exhausts).
My downpipes are PLM, so not sure how the fitting. The installer did very good job but he's been long gone (moving out of the country).
I am dreaded to go back and forth to the autoshops to look for the right tool while the car is in the garage.

Originally Posted by ianthegreat

Yup, I replaced an O2 sensor after a botched DP install once. Never took my car for anyone to work on it again. DIY to ensure quality and peace of mind.

[clairvoyant]

How do you fit that tool onto the O2 sensor?
Do you unplug the O2 sensor wires and trace the tool all the way to the O2 sensors and work your way to remove/install?
Thank You

Originally Posted by ECSTuning

As stated lifting the front of the car should give you enough access to remove the o2 sensor. A wrench like the Schwaben 7/8" Flexible Oxygen Sensor Wrench makes the job a lot easier.

[ECSTuning]

Originally Posted by clairvoyant

How do you fit that tool onto the O2 sensor?
Do you unplug the O2 sensor wires and trace the tool all the way to the O2 sensors and work your way to remove/install?
Thank You

The tools designed to have the wire slip into it before you seat it on the o2 sensor.

[ianthegreat]

Originally Posted by clairvoyant

Yes, these are the post cat O2 sensors (the one closer to the midpipes/exhausts).
My downpipes are PLM, so not sure how the fitting. The installer did very good job but he's been long gone (moving out of the country).
I am dreaded to go back and forth to the autoshops to look for the right tool while the car is in the garage.

I installed PLM DP's also, fit was perfect. The post cat O2 sensors are a peice of cake to remove and replace. Just get the car up on rhino ramps and give it a shot. Might have to make a couple trips to the auto parts store to get the right wrench size, but other than that it's easy.

The ECSTuning rep's tool is a one stop shop correct fit for the plugs, you just have to make sure you can work with the size of that wrench under your car (not sure how big it is, should be ok). I use a 7/8 stubby wrench.

[clairvoyant]

I just ordered that Schwaben 7/8" Flexible Oxygen Sensor Wrench from ECS Tuning. Hopefully they will send it ASAP.
I don't have the luxury to make a couple trips to the auto parts stores in the boondocks where I live.

[ECSTuning]

Originally Posted by clairvoyant

I just ordered that Schwaben 7/8" Flexible Oxygen Sensor Wrench from ECS Tuning. Hopefully they will send it ASAP.
I don't have the luxury to make a couple trips to the auto parts stores in the boondocks where I live.

We just shipped a ton of them out. Shoot me a PM with your order number or email on the account and I'll check to see if yours is one of the ones that shipped out just now.

[Joshboody]

Used harbor freight o2 socket... Like $5, worked great.

[IN54NITY]

Thread resurrection: If you have a Dremmel tool you can simply go to your nearest hardware store and buy a 22mm socket and make your own cut out. I found there isn't much room to move the socket "rotationally" because the exhaust pipes really get in the way of the wrench handle when replacing pre-cat sensors, so the extra "points" (12 instead of 6) of the socket really make a difference.

http://www.e90post.com/forums/showpo...0&postcount=23

[Miller335]

I bought a extra 22mm wrench, cut it in half and just slip whatever size piping over the cut end if you need more leverage.