Need some serious help. Front 02 sensor keeps breaking....

Ok to give u some background info my 09 mazdaspeed 3 had roughly 29k miles on it with all the mods in my sig. And my cars engine light came on and it was for the p0134 code which is the 1st oxygen sensor, bank one sensor one (the expensive one lol) and I brought it to mazda and they took a look at it and replaced the sensor for me now fastforward to today and now my car has 42k miles and only like 8 or 9 months later and the same s*** happened but now that I'm out of warranty they wont replace it for me and I really don't know what could be causing this.

So If anyone could possibly help me out It would be greatly be appreciated.

Thanks in advance

Sounds like your dealer screwed you over the first time, those bastages. ALSO WTF are you running all that bolt-on sh*t WITHOUT a decent tuning device? You have all that Cobb sh*t without the AP.

I know the mazda dealer pretty well and they installed a new one for free. And if u look in my sig I have the accesport lol.

09speed3 said:

I know the mazda dealer pretty well and they installed a new one for free. And if u look in my sig I have the accesport lol.

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OHHhhhh, I missed the AP amongst all the other stuff in your sig. Did you log the front O2 volts to see WTF is going on? Maybe the O2 isn't bad at all? The code says "No Activity". That could be because the connector is dirty or fubared. I would go for the connector since someone has benn in that area to install the intake mods you have. Your ECU is under the hood in that area as well. Sounds like you or the dealer goons need to do some real troubleshooting rather than throw parts at it.... Good Luck!

Well I installed everything on the car except the new 02 sensor. I checked all the connectors and wiring and everything is ok. No splices or anything even touching the wires near the Ecu I made sure of that from hearing all the stories of people putting intakes on it and the clamp cuts into the wire.

I'm gonna go under the car tommorow and take a look again but I'm almost 99% + no wires are messed up. I triple checked everything.

09speed3 said:

Well I installed everything on the car except the new 02 sensor. I checked all the connectors and wiring and everything is ok. No splices or anything even touching the wires near the Ecu I made sure of that from hearing all the stories of people putting intakes on it and the clamp cuts into the wire.

I'm gonna go under the car tommorow and take a look again but I'm almost 99% + no wires are messed up. I triple checked everything.

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I hear ya, but consider that the original O2 failed in a specific manner, of many possible. the replacement failed in EXACTLY the same manner. Also consider that the O2 sensors are not "unreliable" parts that fail often. Did you retrieve and keep the old sensor from the dealer?

Check for vacuum leaks. I know it sounds rediculous, but they can easily throw that code if un-metered air is allowed into the engine.

A few basic background questions:

1. When did you install the Cobb dp, at what mileage and how many miles are on the car now?
2. Related to above question: How long after the dp install did the problem(s) with the sensor - first and/or second sensor begin?
3. I think there are three bungs on the Cobb downpipe. Which bung did you use for that first sensor?
4. And yes, as someone else noted. please log the voltage to that sensor and report the data.
5. Did you AP tune before or after your dp install and which was most closely related to your sensor problem? I'm trying to find out what your setup was before you started throwing this code.

A thought: Since the sensor is also dependent on the ECU for that voltage signal and since you are running AP, you might just want to try a quick reflash back to stock to check voltage in the event there is a problem with your tuning map. But, if your answer to question 4 above shows normal voltage at the ECU, then the problem sounds like it's not in the ECU but in the wiring, connectors or the 02 sensor. Makes me wonder if the wiring or connector issue may have pre-existed your first failure and that that sensor might not have been bad.

A second thought: As another poster pointed out issues on the intake side can throw this code too. Besides sucking in unmetered air, another possibility I've seen on other cars with this code is a bad or dirty MAF sensor, believe it or not. Some Bosch cars like Volvo, Saab and VW's can throw this code with a dirty MAF sensor. While I don't know of a dirty MAF can throw this code on our cars, I'd be checking that too along with checking for air leak sucking in unmetered air.

Hi ok I'm typing from my phone but I'll Trt to answer as best as possible.

1. I installed the dp at around 14k miles I have around 42k now
2. It took around 7 months first sensor even though my car since the dp would always randomly throw the 0421 code which I heard is common
3.the bung was in the dp already so I used the one that was open up top. There's only 2 up top
4 can I log the voltage using the Cobb ap cause I only use the dashhawk to monitor usually.
5 I had the Cobb ap at around 3k miles right after I bought an intake for it.

Before this setup I had everything except the Cobb downpipe and CPe hpfp. Instead of the Cobb dp I had a ********** testpipe. And I was running the same map

I took the Cobb ap off and even disconected the battery and still the same outcome..

I will check everything tommorow. I just understand how it runs perfect for 9 months and then it does the same s*** as it did before.

And thanks for the help I appreciate it.

Looking more and more like you have a damaged wire in the harness going to the front 02 sensor or in its connector. It can look good and still have a break or short or loose connection that would be only intermittent, or initially intermittent and now constant.

The odds of two sensors going bad so close in time seem low, IMHO, but anything is possible.

BTW did you reinstall the heat shield and do it properly after installing the dp? Maybe you are getting too much heat to the harness or the wiring itself? Thermal damage could be something that would take some time to show up.

Also check those connections on the intake side for leaks and see if the MAF sensor needs cleaning.

I don't know what you can monitor with Cobb AP (I'm Hypertech tuned) but you should be able to get front o2 sensor voltage with any good OBD2 reader, including perhaps especially Dash Hawk.

Alright so I as soon as I got out of work today I went straight home and let it sit for about an hour to cooldown.

I went ahead and took the 02 sensor out and it had a layer of black s*** all on it. A couple of the holes looked cloged so i went ahead and cleaned it to the best i could. I reconected the battery and started the car up and the AFR worked! But it went to about 9.1 at idle so i shut it off and restarted it and gave it alittle gas and it went back to normal. So I took it for a 15 miles test drive and everything appears to be fine. I really wonder if this has fixed it or its just temporary because I drove it all day today and the AFR was stuck at 14.81 and my stft and ltft would just show 0.0

Update put 140 miles on the car today and everything is working still

Put another 80 miles and still running good

So you saved yourself from buying ANOTHER O2 sensor. Just FYI, whatever is causing the excees carbon buildup will continue and you'll likely need to clean it again sometime in the future, so don't let the stealership screw you over again. IMO, the original O2 is/was fine as well...... You NEED a better tune AND you have the AP, so no reason not to clean up the exhaust.

Well the tune is really good in the summer but I guess it doesn't like the cold weather to much and since I do alot of highway driving it doesn't help.

I dynod 301 hp and 313 tq with the same tune and mods

And I guarantee the 1st 02 sensor was just extremely dirty but Mazda replaced it for free so it wasn't that big of a deal. But this time I was like how in the hell is it messed up already lol

And thanks for the help It was much appreciated.