Just bought an 07 fit with 84k miles. The guy I bought it from claimed it had a check engine light for the O2 sensors but that he replaced both the sensors, so I should be good to go. It was good for a while until about 1000 miles later the check engine light came on. Took it to autozone and the error code P1172 came up. I’ve read on that code and it’s very confusing to understand.

Anybody have experience with this code and what to do?

 

That code means that the downstream O2 sensor (the one plugged into the catalytic converter) is reading out of range on the high side. Did the AZ dude take a real-time reading of the output of the sensor to see what it was doing, or did he just pull the code? The downstream O2 sensor isn't particularly critical to engine function, as it's just there to monitor the output of the catalytic converter, so not a panic situation. I'd just clear the code and see what happens (well, actually, I'd watch the output of the O2 sensor using Torque and my OBD dongle, but only us gearheads keep those toys around). If it's a failure that keep happening, it's quite possible the guy cheaped out and bought some crap sensor instead of spending a little extra and buying a Denso (FWIW, I'm a bit fan of Rockauto for these sorts of parts).

 

yeah I think it’s a cheap sensor. I think he said he got it off EBay. I’ve tried unplugging my battery then plugging it back in to clear the code. Check engine light comes back on within about 10 miles.

it doesn’t affect engine performance at all. Do you think I should just buy a Denso sensor and see if that fixes it? And if so, where would I find the exact sensor to purchase?

 

If you don't have the tools to monitor the output of the sensor, that's probably your only option. Go to the Rockauto site to find your sensor - they've got a real good cross reference. I just changed out the downstream on my '08 recently - it was Denso part 234-4358, cost about $70 plus shipping. The '07 probably uses the same part. If they don't have the Denso, the NTK is also a good part (just make sure you get the downstream, not the upstream sensor). I'll warn you tho - changing the sensor is a minor bitch, as you have to pull out the center console to get to the connector.

 

I think I found it on Amazon. [url=http://Denso 234-4358 Sensor de oxígeno (sensor de relación de aire y combustible) [ame]https://www.amazon.com/dp/B001F7CF4G/ref=cm_sw_r_cp_api_glt_fabc_64TN32YK7S3QXF912B0C?_ encoding=UTF8&psc=1]Is this the right downstream one?[/ame]

Only reason I’d go with Amazon is because they have like 2 day shipping and if it doesn’t work I think I can send it back and get my money back.

 

Yeah, that's the correct part #. Personally, I've stopped buying auto parts on ebay and Amazon -- the fake parts have just gotten too hard to tell apart from the real deal. But it's your money.

 

just took it by OReilley and and had them pull use their obd reader just to be sure before I buy the downstream O2 sensor. And their OBd reader read P2a00, which is showing bank 1 sensor 1 (upstream sensor). Now I’m more confused than ever. Should I just replace both sensors?

 

OK, I apologize -- both your original code (P1172) and the current code (P2A00) indicate a range issue with the upstream sensor. Which sucks in one regard (as that's the expensive A/F sensor), but nice in another (it's slightly easier to install). Again, without being able to monitor the output voltage of the sensor with an OBD reader, it's tough to troubleshoot this without shotgunning the part, although the basic step of unplugging and replugging the sensor is always worth trying (hardly ever helps, but it's a cheap thing to try). Does the guy you bought the car from still have the old A/F sensor? If it still works, then you could at least swap with a "known good" before putting out $150 (or whatever those A/F sensors are going for these days).

For now, I wouldn't mess with the downstream sensor if you're not getting any codes for it