Hello, I'm new to this community, but I wanted to reach out because my husband and I have been trying to figure out what's wrong with my car for about 2 months now. Sorry in advance for the lengthy post.
This all started in July when my check engine light came on and my husband hooked up his obd scanner to it and we got the code p2096. So I took it to my parents neighbor who is a mechanic and he cleaned the 02 sensor and pointed out that there was a badly welded seam on the exhaust pipe. And then we took it to a shop to have the weld fixed. After that, p2096 persisted. So I bought a new downstream o2 sensor off Amazon which was the exact item recommended by the neighbor mechanic. This o2 sensors brand is Dropwater and it costs around 30 dollars.
While waiting for this item to arrive, I had my oil changed by the same neighbor. He changed it but forgot to secure the oil cap tightly and I had no idea. 3 days later, my roommate points out that I was leaking oil from the car onto the driveway. So my husband popped the hood and discovered the oil reservoir cap was not there and oil was everywhere. I had almost no oil in my engine upon discovering this. We immediately got more oil and a new oil cap.
Subsequent to this, I started to notice choppy acceleration, bad gas mileage, and engine rumbling.
And that same mechanic had previously recommended getting a transmission exchange, and not trusting him anymore after the oil fiasco, I decided to take it to Big O Tires where I had them exchange the automatic transmission fluid, and install the new o2 sensor which they did. Later that day, the engine light came back on, and my husband ran the obd scanner again, and now we were not only getting p2096 but also p0137.
So my husband did some research on the mazda forums and found that p2096 is a sometimes a known issue with mazda 2s and 3s and can be solved by detaching the battery leads from the battery and touching them together for 10 seconds. After that, he reattached the leads and the next day the engine came back on. But upon attaching the obd scanner, we discovered that p2096 was no longer an issue but p0137 remained.
Because we had a new downstream o2 sensor, and my husband had read p0137 can be caused by contaminants in the harness, he wanted to visually inspect the plug for the new 02 sensor and the matching harness for the car. So he went underneath to try and unclip the harness, amd found that the catalytic converter was still unreasonably hot, even though by this time the engine had been off for over an hour amd it was getting dark out. Because of the heat and constricted environment, he was unable to unclip the sensor plug from the harness.
The next day, I spoke to a mechanic friend (not my parents neighbor), and described for him the situation up until that point, and he seemed confident that it was a problem with the catalytic converter. He recommended we take it to a muffler shop and have them run a diagnostic check to see if the catalytic converter was bad. The mechanic at the muffler shop recommended we get new spark plugs and a new different o2 sensor that was a name brand (denso or ngk and not a cheap brand). So we got new ngk brand spark plugs which my husband installed, but we did not get a new o2 sensor. I also bought some duralube and fuel injector cleaner and put those in that day as well.
For about a day, the car ran excellently without the engine light coming on. After that, the engine once again came back on, and the old problems of choppy acceleration, bad gas milage, and engine rumbling returned. P0137 still...
So tonight, my husband and I decided to remove the battery and battery case to gain better access to the downstream o2 sensor harness to inspect it for damage or debris lodged into the harness itself. We did that, amd it looks fine. We checked the voltage on the obd scanner for the o2 sensor and it had a range of about 720 to 760 milivolts. We have read on the internet that the normal voltage is about 450 mv, so that's a big difference. Are we understanding this correctly? We aren't sure.
Our next step is to replace the o2 sensor with a brand name one, and if that doesn't work, move on to possible catalytic converter replacement. Now I'm asking you guys what do you all think? Are we wasting our time and money getting a new o2 sensor? Or do you think that may likely be the issue? If not, what about the catalytic converter. But if neither of those, what else could it be? Is it possible that the neighbor mechanic oil fiasco could have something to do with it? Are we missing anything? Please help! Thank you!!!!
Car specs:
2010 mazda 3
2.0 liter
130,000 miles
Well maintained, but drive it a lot for work
This all started in July when my check engine light came on and my husband hooked up his obd scanner to it and we got the code p2096. So I took it to my parents neighbor who is a mechanic and he cleaned the 02 sensor and pointed out that there was a badly welded seam on the exhaust pipe. And then we took it to a shop to have the weld fixed. After that, p2096 persisted. So I bought a new downstream o2 sensor off Amazon which was the exact item recommended by the neighbor mechanic. This o2 sensors brand is Dropwater and it costs around 30 dollars.
While waiting for this item to arrive, I had my oil changed by the same neighbor. He changed it but forgot to secure the oil cap tightly and I had no idea. 3 days later, my roommate points out that I was leaking oil from the car onto the driveway. So my husband popped the hood and discovered the oil reservoir cap was not there and oil was everywhere. I had almost no oil in my engine upon discovering this. We immediately got more oil and a new oil cap.
Subsequent to this, I started to notice choppy acceleration, bad gas mileage, and engine rumbling.
And that same mechanic had previously recommended getting a transmission exchange, and not trusting him anymore after the oil fiasco, I decided to take it to Big O Tires where I had them exchange the automatic transmission fluid, and install the new o2 sensor which they did. Later that day, the engine light came back on, and my husband ran the obd scanner again, and now we were not only getting p2096 but also p0137.
So my husband did some research on the mazda forums and found that p2096 is a sometimes a known issue with mazda 2s and 3s and can be solved by detaching the battery leads from the battery and touching them together for 10 seconds. After that, he reattached the leads and the next day the engine came back on. But upon attaching the obd scanner, we discovered that p2096 was no longer an issue but p0137 remained.
Because we had a new downstream o2 sensor, and my husband had read p0137 can be caused by contaminants in the harness, he wanted to visually inspect the plug for the new 02 sensor and the matching harness for the car. So he went underneath to try and unclip the harness, amd found that the catalytic converter was still unreasonably hot, even though by this time the engine had been off for over an hour amd it was getting dark out. Because of the heat and constricted environment, he was unable to unclip the sensor plug from the harness.
The next day, I spoke to a mechanic friend (not my parents neighbor), and described for him the situation up until that point, and he seemed confident that it was a problem with the catalytic converter. He recommended we take it to a muffler shop and have them run a diagnostic check to see if the catalytic converter was bad. The mechanic at the muffler shop recommended we get new spark plugs and a new different o2 sensor that was a name brand (denso or ngk and not a cheap brand). So we got new ngk brand spark plugs which my husband installed, but we did not get a new o2 sensor. I also bought some duralube and fuel injector cleaner and put those in that day as well.
For about a day, the car ran excellently without the engine light coming on. After that, the engine once again came back on, and the old problems of choppy acceleration, bad gas milage, and engine rumbling returned. P0137 still...
So tonight, my husband and I decided to remove the battery and battery case to gain better access to the downstream o2 sensor harness to inspect it for damage or debris lodged into the harness itself. We did that, amd it looks fine. We checked the voltage on the obd scanner for the o2 sensor and it had a range of about 720 to 760 milivolts. We have read on the internet that the normal voltage is about 450 mv, so that's a big difference. Are we understanding this correctly? We aren't sure.
Our next step is to replace the o2 sensor with a brand name one, and if that doesn't work, move on to possible catalytic converter replacement. Now I'm asking you guys what do you all think? Are we wasting our time and money getting a new o2 sensor? Or do you think that may likely be the issue? If not, what about the catalytic converter. But if neither of those, what else could it be? Is it possible that the neighbor mechanic oil fiasco could have something to do with it? Are we missing anything? Please help! Thank you!!!!
Car specs:
2010 mazda 3
2.0 liter
130,000 miles
Well maintained, but drive it a lot for work
