Has anyone replaced either side upstream o2 sensors from the top down? Its pretty damn hard to get to on the bottom and its freezing outside. Just wondering if I could take off the intake or something and be able to reach down to them..

Not likely. Even if you could, you might not have the leverage to break them loose. Prolly could pull the y-pipe and cat out of the way to get to them. Might be able to get them without moving anything.

Damn...That thing is so damn hard to get to. Took me a couple minutes to even find it, but it was way to cold for me to function enough to remove it lol

I threw a code for one of mine too. Cleared it, and it hasnt come back. But that just means its coming up soon. Im not looking forward to doing that at all :/

Yeah I've cleared my ECU a few times, it keeps coming back every couple days.

My problem is the ECU is throwing the P1283 code for bank 2 upstream running lean, with my scanner I monitored all the votlages and its showing that bank 1 upstream o2 is actually the one running lean (stays around .3 volts and responds slowing as opposed to bank 2 .45 volts)

So I think I'm going to replace the bank 1, I'll be pissed if its not that one though lol

So replace both upstream at the same time. Then you don't have to go underneath twice. They're both being fed the same amount of air to monitor. If you can afford to get both, save yourself some time and frustration by doing them together.

Yeah, I was kinda curious though why my ecu says one thing and my readings say another.

Definitely would be easier going from the bottom, there are too many things in the way if you try to go through the top.

The upper sensor in the down pipe is the lambda the ECU uses to trim fueling during closed loop, the lower is used to monitor the cat condition, and not fueling, i have the lower sensors removed and running wide band sensors in there, the ECU throws a code but they have no effect on fuel trim.

I think it's impossible from the top, and not too hard at all from the bottom. Make sure you check the harness on the plug (which you access from the top) before you get under there, though. You'll find most of the aftermarket sensors come with the incorrect harness. If you're unsure of which sensor to order, it's the expensive one.

I believe Infiniti charges $165 for their sensors, replacing both is retarded when the one throwing the error code is the upper on right side. (passenger) Replacing it from above is almost impossible, it's not even easy from the bottom. You could buy the sensor and have your local muffler shop replace it for you for a couple $$ since they have the rack and right tool for the job.... Gary

where are the sensors located?

If you look under the car, they are before the CAT. Going up towards the engine.

​​​​​​was it the drivers or passenger upstream 02 you replaced?

Not worth the effort from the top. And if it's cold it's cold whether you're on the ground or hanging over the engine. Look for a big piece of cardboard - fridge or appliance size would work nicely.