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Hi,

I have a 2010 Mazda 3, 2.0 L Sedan and the check engine light turned on a couple of days ago. I did a scan with Bluedriver and it came up with the code P0134. The report said "O2 Sensor Circuit No Activity Detected Bank 1 Sensor 1." How do I check that the problem is the Oxygen Sensor and not something else?
 

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Super Moderator
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Hi,

I have a 2010 Mazda 3, 2.0 L Sedan and the check engine light turned on a couple of days ago. I did a scan with Bluedriver and it came up with the code P0134. The report said "O2 Sensor Circuit No Activity Detected Bank 1 Sensor 1." How do I check that the problem is the Oxygen Sensor and not something else?
Check for broken wires. Is the O2 sensor connector plug loose? Does the car run ok? Could be low fuel pressure, a leak in either the intake or exhaust or the coolant temp sensor is bad. However, usually its a bad O2 sensor that triggers this code.
You can search for this OBD2 code on line and find diagnostics for it. You will need a good DVOM to do most of the testing on the O2 sensor.
 

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Demon Spawn
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758 Posts
arathol, you are just like me man. beat me to the suggestion, bad thing to the op is usually when they throw no activity codes the sensor has failed, and you don't wanna drive too much with a bad o2 sensor as it controls the air fuel ratio for the car by letting the computer know if its running rich or lean and making adjustments well front o2 sensors are heated hotter than the exhaust and get cooled as the exhaust passes them, well the cooling makes the senor start detecting the oxygen levels in the exhaust and it sends patterns of 1s and 0s to the computer constantly to let it know to put in more fuel or less fuel in the mix. if this is not functioning properly you can run too rich and dump raw gas into your cat. converters and ruin them costing a lot more to fix. if you run lean you can cause other issues in the engine such as misfires and other stuff you don't need, it can also make the cats run hotter than normal and burn them up faster. I would suggest as Arathol already has to get under and check the wiring and plug for cuts or a loose plug if none are found get a new o2 sensor and change it. get denso or NGK/NTK avoid bosch o2 sensors in Japanese cars they tend to not work as well for some reason, but are fine in other countries cars. bank1 sensor 1 is closest one to the engine in the exhaust, you should be able to see the wires and connector and everything under the hood, and may even be able to change it without lifting up the car. you need either an 02 sensor socket (socket with a slit for the wiring loom) or a 22mm/7/8th inch (same size) open end wrench to grab the senor and pull it out, maybe some pb blaster as well as they usually rust in pretty hard and don't wanna break free.

the top image in this diagram should be your cars o2 sensor setup (2.0 federal emissions): https://www.mazdamotorsports.com/wcsstore/B2BDirect/images/catalog/section/3B26713_1000.gif


this is an 06 2.0/2.3 diagram but not much changed from 04-13 on the non skyactiv engine components so the diagram should be fairly accurate. the part labeled 1310 in the diagram is your exhaust manifold find that and you will see wires running down to where the pipe for the exhaust comes out the sensor closest to the engine is the one you want. you will then see the wires run to a metal head that bolts into the exhaust pipe near the manifold (maybe on the manifold itself but somewhere right there) pb blaster helps get this unstuck, what you are looking at is the outer part of the o2 sensor only a tiny probe parts sticks into the pipes most of it is outside the exhaust, wires will run right to the middle of it then it will turn to a metal sensor head with a nut on the end that connects to the manifold/pipe undue the nut pop the sensor out and follow the wires back to find the plug, unplug it plug new one in and bolt it down, its that easy. make sure before bolting in the new plug the threads have antiseize on them (should come on the threads of the new sensor but sometimes they forget) its a grey paste if your unfamiliar, pick up a small pack from the parts store before you install just in case the sensor does not have any, make sure it goes around all the threads (don't get it on the sensor probe) and then install. driving 3 drive cycles of about 50-100 miles each should clear the code or you can ease with the reader and see if it comes back.
 
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