I need to change oxygen sensors in my Mazda 6 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 ?

 

Its very close to the head of the engine just slightly down from the beginning of the exhaust manifold.

 

Hi,

From all videos I gathered, and looking at the parts, this is the location of downstream sensor, you can even see it on my pics.

I am looking for the location of upstream sensor.

 

Yes, and that is what I described. The HO2 bank 1 needs to be at are very close to the primary or front CAT. The one you mention which is Bank 2 is post CAT and basically read the oxygen after the CAT.

BTW the DTC having to do with HO2 is one of the most often misdiagnosed parts from DIY that often jump to the conclusion based on YouTube info or non professional based service manuals part replaced before confirming they are the cause of the DTC. Often times when replacing them with new HO@ the problem originally was not solved and unless the NEW parts were first verified as not having any problem as in a good part will add to the already unresolved issue.

Your pictures are not showing the hard to reach area where the primary Bank 1 HO2 is, re-read my first response again and go look with a flash light if anything else jack the front up get under the Mazda and look for the HO2 wire harness and follow it to the HO2 by the CAT!

 

I re-read your message, and I went back to check the car.
I took more pics following, starting from the top.
I followed it down to the sensor which is short downstream sensor.
I'm still unable to find the upstream bank sensor.
I even made comparison pic for you, using videos from Youtube of same MZR GH Mazda 6, please see below comparison, I don't have anything where the upstream sensor should be.
I tried to find that connector on top and follow it, however I'm unable to find that connector.
I jacked up the car, and all I found is a whole in exhaust close to downstream bank sensor, I have to fix that.
I will take more pics tomorrow from under the car as it's getting dark now and I don't have a garage.

 

First disregard my "BANK" usage for wording it can confuse many and technically not for a 4 cylinder.

HOWEVER your forward or upstream sensor (HO2 or O2) will be in front of the CAT plain and simple.

If you are getting a DTC specially for the upstream HO2/O2 then you have one. Plain and simple. You can also verify this information by using your diagnostic scanner connected to the diagnostic connector and looking for the ho2/o2 sensor information. If it shows one or the other N/A then you don't have that sensor.

I am sorry, but the USA version of your Mazda has both I don't have UK or Mazda marketed for outside the US and Canada what they did or did not have for standard emission controls. Technically speaking in USA your Mazda would likely be a grey market vehicle and therefore difficult to register and license here so service information for some platforms is not complete for all service information.

The very last picture in your previous response appears to have a sensor in the back ground?

 

Right, my apologies, I should be more specific in what I wrote in my original post.
I am not getting the error for the upstream oxygen sensor, or if I do, I'm not aware as I didn't check.
I simply started googling symptoms that started happening with my car, which pointed to Oxygen Sensors.
Especially that they were never replaced, and the car just hit 110 000 miles.
I know I should start with reading the codes from the car, I simply decided to replace them because I thought it's time to do it anyways.
I typed my vehicle reg. on automotive car parts website, and I could find two sensors, hence why I ordered two.

Before that I did the service, replaced all filters and oil, changed spark plugs, cleaned the MAF sensor.
However the car still have the same symptoms - sometimes have hard start (not always), oscillating idle, car suddenly have no power on low rpms like something is holding it, and suddenly it let go and jerks forward with full power, car sometimes dies when decelerating, the RPM goes below 500 and the engine stalls.
All of the above symptoms I'm having are random, this does not happen all the time. Sometimes car is ok for 1 day, then next day all symptoms are there, and on day 3 only one symptom shows.
I better go and read the codes as I know you will tell me I'm silly for replacing something I don't even know if I need replacing :P

 

oooooohhhhhhhhh1 LOL

Well I suggest in the future always check the ECU in active DTC(s), permanent DTC(s) and then you're I/M monitors long before you start replacing parts.
As for the internet I find flaws in service advise everyday from members on various forums using them.
Always confirm a part is the problem before replacing it. This BTW is sign of a quality service shop if you leave your car and they charge you for parts and then still claim not to have resolved the issue.
As for HO2/02 technically and most are very high quality material and components (need to carefully or better wisely choose the brand) they should go 150k-200k miles but unfortunately their longevity is directly influenced by the preventive or scheduled general maintenance that is seldom done.
In your case without first knowing the ECU reports you could have something more mechanical then ECU or sensor related???

 

I completely agree with you, and I’ll definitely follow your advice.
I ordered an OBDII scanner yesterday, and it should arrive today.
Once it’s here, I’ll check the fault codes and share the list with you—hopefully, it’ll be a short one!

 

ok....