Ilya wrote: ↑

Fri Jan 13, 2017 3:50 pm

Yeah the top two are a PITA to change...I didn't even bother changing them on my 07. Just did the bottom two. If I ever had to change the top one on this car, I'd have to bring it to the dealer. I have a LOT of tools and I don't have ANYTHING that would be able to reach in that spot and undo the sensor and then screw it back in...and there is no way to get at it from the top that I know. It's an insanely terrible design. Bottom two are easy.

PITA, yes, worth having the dealer rape your pockets, NO. LOL

After reading this post I went poking around at mine after getting a P2A03 code.

To replace O2 sensor (A/F sensor) on 2011 Infiniti M56s (Bank 1, sensor1).

Took me about 2-3 hours, including the picture taking.

Use jack stands so you don't drop the car on your head and do it with the engine "frost of the morning cold" you are going to get very intimate with that exhaust pipe.

The image below shows the tools needed:

Impact driver 1/2 inch drive (could use a breaker bar but driver is easier)
10 inch extension bar (1/2 drive)
Swivel joint (1/2 drive)
5 inch extension bar (1/2 drive)
1/2 drive to 3/8 reducer
swivel joint (3/8 drive)
22mm O2 socket 3/8 drive.
14 mm socket (3/8 or 1/2 drive)
Swivel ratchet (3/8 or 1/2 drive)
Torque wrench (new sensor is recommended to be torqued to 38 ft lbs)

Part number for O2 sensor: 250-25105 (Walker Brand) Cost $140 on Amazon and came with a one year warranty.

YOU WILL NEED AN EXTRA SET OF HANDS, THIS REQUIRES COORDINATION FROM BOTH ABOVE AND BELOW. ALSO YOU REALLY SHOULDN'T BE UNDER AN ELEVATED VEHICLE WITHOUT SOMEONE WATCHING YOUR BACK.



I used two low profile jacks and one regular jack with a cross bar to elevate the car. Use jack stands as shown to supplement/stabilize the cross bar so the car isn't teetering on just the jack at the rear.




This the view of sensor one, bank one from the top down

And from the bottom. Foreground left is sensor two.


String your extensions pictured way above in the following order: 10 inch extension bar (1/2 drive)>>swivel joint (1/2 drive)>>5 inch extension bar (1/2 drive)>>1/2 drive to 3/8 reducer>>swivel joint (3/8 drive)>>22mm O2 socket.

That rig will get you from here: (green dot is the O2 sensor connector for sensor one) Your angle of attack is going to be steeper than pictured:

To here:


Your gonna have your helper hold the rig from the top while you guide it onto the sensor from the bottom, Space is tight, you'll have room for one hand and will be working almost blind.

I removed the bolts (14 mm) on this exhaust bracket to get a few more inches of working space (its attached to a harness, I just let it hang. No need to detach the harness clip, I got all I needed as is:



Impact wrench will break it free, and swivel ratchet will unscrew it the rest of the way:


Install is reverse, guide it from the bottom and have your helper screw it in from the top using the same rig setup. New sensor in place.


Hope this helps.

Sensor cost me $140 on amazon. Infiniti wanted $300+ but the parts guy pissed me off when he told me they "don't give out part numbers" so I cut that convo short. I had a list of more vulgar things he could do to earn $300 bucks from me at that point (I was nice and kept it to myself). After all, it's not like they redact the part numbers off the box. I'm gonna get it anyway (and already had it before I called).

If there was a 'vote for best post' feature I would vote for this one!

Well done and much appreciated!

Seriously. I think I can manage this now should I get that code (I've been getting the P0420 code in the winter so my cats are likely on their way out and not my sensors). Awesome job.

As for getting part numbers...I just use the diagrams on InfinitiPartsUsa.com for that type of stuff and then search that # on eBay or Amazon and buy what's cheapest. Screw the dealer.

EDIT: One suggestion though, can you edit your original post to break down the parts like in the other HowTo's? That way if someone prints the page, they have the parts needed at the top in case they have to go shopping, etc.

Here is an example: howto-replace-pcv-valve-m56-vk56-t604225.html

Not a problem. Will do.

Pimperish1 wrote: ↑

Wed May 02, 2018 9:21 pm

Not a problem. Will do.

You can copy-paste your info from the first post, and move things around as you please then post it below here. We'll find it and put it at the top.
... or a new thread.
Whichever is most convenient for you to do. Thanks for the effort.

Thank you sir, I've updated the original post and deleted the edited version for organizational purposes. Really appreciate it. Write more stuff . We can never have enough DIY's!