Which o2 sensor to replace??

[Andalf]

Hello all,

Fair warning to all, that I'm a complete forum and car newb, but i'm pretty handy and like to get my hands dirty.

I've had a CEL for the past couple of months, It's been coming and going, but lately mostly coming..

So I got the code read again, it's showing P0131, P0134, and P2251(not certain about the last one). but either way, googling all of these, they all seem to relate to the o2 sensor(s).

I know there's the blatantly obvious one that you can see from the top when you've got the hood open - if it's that one that needs replacing that's awesome, I can save a few bucks doing it myself. But I don't know where the other o2 sensors are or what they're all called, so I'm worried that I spend 150-200 bucks to replace the wrong sensor...

Can anyone help me save a few bucks by telling me which sensor those 3 codes are most usually associated with?

And where that sensor is on a 2007 Mazda 3 2.0L? (Pictures would be stellar!)

Any and all help is very well appreciated!!!!

Thanks

[Hyperion]

The second one is 10 inches further down.
P0131 is your primary though anyways, the one that you can see. Also the more expensive one. It's like 300 from the stealership. I'd suggest rockauto.
Also, good luck getting it out, the heat and tends to weld them in.

[Andalf]

Thanks Hyperion,

I see the 2nd one now, I thought there were several though(>2)??

And are you saying the P0131 is definitely associated with the "Primary" one? (don't worry, I know even if it is, the CEL could be getting thrown by the wiring or other stuff, so replacing the sensor isn't guaranteed to fix anything... )

Also, I assume that lower one is the one they refer to as 'downstream'?
When I was asking around for prices, I was definitely emphasizing "Primary" but may have also told them "downstream" because I thought the others were all upstream of that primary one... Makes sense now why the stealership told me 177, partsource 200, but the local ma' and pa' mechanic told me 295.

I'll call them all back and clarify...

Thanks again!

[loki]

I didn't google the codes because you've already done that but bank 1 is the primary and bank 2 is the secondary

Regardless of which sensor is toast (if thats even the case), if you want to get it out without royally f****ing it up I strongly suggest at least 1 week in advance of when you plan on taking it out, start spraying it with pb blaster every chance you get. Yes you'll have a smoke show but it helps alot. What's just as important is the right socket piece. You want the one that grips all the way around not the open ended one, less chance of stripping th3 sensor...I have a really good one that boyracer bought for me as a gift (speed3 guys are such a$$holes that we give each other cool stuff) maybe you can ask him where he got it. Might have been princess auto.

anyway you can get the O2 sensors online for alot cheaper you just need to know which one to buy. CelestSpeed3 knows. Hell he might even have one lying around you could buy.

[boyracer]

I bought the socket set from Canadian Tire, it's a set of 3 & well worth it. I've included the link below (cause we're such a$$holes) so you can get an idea of what you would be looking for.

http://www.canadiantire.ca/checkinventory/check_inventory.jsp?CTC_INPUT_POSTAL%3C%3Estore_no =0152&CTC_INPUT_POSTAL%3C%3Epostal_code=L4Y2C1+&CTC_INPUT_POSTAL%3C%3EfromChkInv=true&PRODUCT%3C%3Eprd_id=845524443306064&PRODUCT%3C%3Eprd_id=845524443306064&FOLDER%3C%3Efolder_id=1408474396672077&bmForm=form_checkInventory_make_my_ctc_store&bmFormID=1381749276369&bmUID=1381749276369

[Andalf]

Thanks guys, the link was dead but I know of the socket set you're referring to, was thinking of trying partsource for their loaner program depending on the price difference.. or trying w/ an adjustable wrench or vice grip.. thx for the tip about the pb blaster too.

digging more into the P2251 code tho, I found this :

I'm assuming A/F is the air fuel ratio sensor? does "The PCM detects the DTC P0134:00 while the pending code P2251:00 is stored." mean that this A/F sensor code is triggering the o2 sensor code?

P2251A/F Sensor Negative Current Control Circuit OpenClose Details
CONDITIONS FOR SETTING THIS CODE:
The PCM monitors the A/F sensor terminal F voltage. If either of the following conditions are met, the PCM determines that the A/F sensor negative current control circuit is open. MONITORING CONDITIONS ¦The A/F sensor element impedance specified or more. ¦Circuit voltage oscillation or A/F sensor terminal F voltage is below the specified. ¦The PCM detects the DTC P0134:00 while the pending code P2251:00 is stored.
POSSIBLE CAUSES:
A/F sensor connector or terminals malfunction PCM connector or terminals malfunction Open circuit in wiring harness between A/F sensor terminal D and PCM terminal 2AC A/F sensor malfunction PCM malfunction

[jay93]

global auto parts


4000 Steeles Ave W, Woodbridge, ON L4L 4V9
905-850-8850

check these guys out for your o2 sensor. i payed $130.00 for my primary and the brand was ngk.
so save yourself a bunch of money

[stock3]

Thanks guys, the link was dead but I know of the socket set you're referring to, was thinking of trying partsource for their loaner program depending on the price difference.. or trying w/ an adjustable wrench or vice grip.. thx for the tip about the pb blaster too.



You were just given the most useful advice about this job by loki and you want to try an adjustable wrench or vice grips? Hey maybe plumbers wrench will work too.

Get the right tools first, if not just get someone else to do it. Don't get me wrong, I'm all for improvising or being creative with the tools I have instead of buying one time use specialty tools, but O2 sensors are special and you don't want to mess up that job. They can come out fairly easily or very hard, it all depends on how much prep and what type of socket you use. Listen to the good advice given above and get the right socket or rent it. Also, soak that sensor every day, for several days with good penetrating oil.
Remember that it's not just the sensor that you may mess up, but the threads on the exhaust manifold can be messed up just as easily. You don't want to mess up the threads on the exhaust manifold.

[Hyperion]

You were just given the most useful advice about this job by loki and you want to try an adjustable wrench or vice grips? Hey maybe plumbers wrench will work too.

Get the right tools first, if not just get someone else to do it. Don't get me wrong, I'm all for improvising or being creative with the tools I have instead of buying one time use specialty tools, but O2 sensors are special and you don't want to mess up that job. They can come out fairly easily or very hard, it all depends on how much prep and what type of socket you use. Listen to the good advice given above and get the right socket or rent it. Also, soak that sensor every day, for several days with good penetrating oil.
Remember that it's not just the sensor that you may mess up, but the threads on the exhaust manifold can be messed up just as easily. You don't want to mess up the threads on the exhaust manifold.

This

[Andalf]

You were just given the most useful advice about this job by loki and you want to try an adjustable wrench or vice grips? Hey maybe plumbers wrench will work too.

Get the right tools first, if not just get someone else to do it. Don't get me wrong, I'm all for improvising or being creative with the tools I have instead of buying one time use specialty tools, but O2 sensors are special and you don't want to mess up that job. They can come out fairly easily or very hard, it all depends on how much prep and what type of socket you use. Listen to the good advice given above and get the right socket or rent it. Also, soak that sensor every day, for several days with good penetrating oil.
Remember that it's not just the sensor that you may mess up, but the threads on the exhaust manifold can be messed up just as easily. You don't want to mess up the threads on the exhaust manifold.

Lol ya, I didn't notice before how the nut was mostly hidden under that heat shield or whatever it is... otherwise, I've got a big 'ol adjustable wrench that would have been perfect lol ;).

Either way... Partsource had those little sockets for 15 bucks so I picked one up anyway.

Ended up getting the sensor from the dealer(westowne) because with the TM3 discount it was slightly cheaper than the NGK replacement that they sell at partsource and they insisted it wasn't made by NGK or bosch so I thought the mazda part would be safest...

All in all went as smoothly as I could have asked for. I've only done about 25km since so I guess we'll have to wait and see if the CEL comes back (*fingers crossed*).

thanks again to all who posted for the advice, it is very well appreciated (Even the sassy one about not using a wrench lol - I can tell it was well intentioned)