Identifying Upstream Oxygen Sensor Location

[Moteje]

Hi guys,

I need to change oxygen sensors in my Mazda6 (GH 2008 TS2 Petrol 2.0 MZR) as I'm getting all symptoms of faulty oxygen sensors. I ordered both of them - upstream and downstream one. I quickly located downstream sensor looking at videos on youtube, but in the location where I should have upstream sensor, there is nothing!

Please see pictures below from the engine bay, can anyone help me finding the upstream sensor?

Or is it possible that someone removed it?

 

[ADS-B]

Look for the exhaust manifold and remove the exhaust manifold heat shield. I believe I can see the heat shield in the first picture.

 

[Moteje]

I don't think my engine has a heat shield.


I've attached a comparison image I created, based on tutorial videos for replacing the upstream bank 1 sensor on Mazda GH MZR engines, along with a photo of my own engine. In the location where others have the upstream sensor, there’s nothing. Additionally, there are no bolts or mounting brackets for wiring of the sensor, which makes it look like it was never installed.


Could it be possible that my engine simply doesn’t have an upstream bank 1 sensor?

 

[ADS-B]

That’s the heat shield. Otherwise you would see the exhaust manifold, four pipes coming out of your engine block. I would remove the heat shield and probably the sensor is underneath. The other picture it’s from a newer engine, probably a Skyactive engine, after Ford era. Your car is from 2008, different engine, different layout.

 

[Moteje]

There is no space for anything beneath what I posted.
The comparison I made is for the exact same type of engine.
On the picture on left you have 2.5 Mazda 2010 MZR GH and on mine you have 2.0 Mazda 2008 MZR GH.
Both engines have interchangeable parts, as I checked.
All videos for MZR Petrol engines look the same for 1.8., 2.0 and 2.5 engines.
Skyactive engines were used from 2011.

 

[ADS-B]

Looking again at the picture named “ my engine” I see two bolts looking down, half way down on that shield. I am thinking that maybe one of those bolts plugs the O2 sensor hole. The easiest way to answer your question, in my opinion, is to remove the shield. You should see the catalytic converter and I am hoping that there is the hole for your missing sensor.

 

[GrampaSlade]

According to what I can find, the upstream is just in front of the flange where the cat bolts to the exhaust manifold. Is that not it in photo number 2?