Hey all, new guy here. I accidentally posted this on the Newbie thread, go figure .
I bought my Fit about a month ago, thought I got a good deal, but turns out I was a bit mislead. ~130k miles. It has a clean title, but now that I've been in it more there are definitely signs it was in a wreck at some point. My main concern right now is that I keep getting a downstream O2 sensor bias stuck lean code. I replaced the sensor with an OEM sensor hoping it would fix it, but no luck. It will run about 3-4 on/ off cycles after clearing the code before it comes back. This week I tried checking the exhaust system for a leak, but couldn't find one. Then I adjusted the valve lash, and replaced the spark plugs, still no luck.
Before valves and plugs it was getting about 30-31mpg mixed driving, now 31-32mpg. I feel like it is dumping more fuel because it thinks it is lean because I thought mpg should be a bit better.
What am I missing, or what else could it be? Thank you for your help.

 

Generally the ways that will cause a car to go lean are too much air not enough fuel.

is your car modified or stock?

have you checked for any potential intake leaks?

 

It seems to be stock, and I have not checked for intake leaks. I figured if it was intake, wouldn’t there be a code for the upstream sensor rather than the downstream? I may be misunderstanding, but the stuck lean is showing the relative readings between the sensors, right?
I’ve wondered about injectors, but wouldn’t it be running rough if that was an issue?
thanks for help and ideas.

 

I would find it odd for the injectors to cause that code. In my experience on these cars, the injectors work or they don’t, when they don’t you’ll know it. I’m just wondering if maybe there is a disconnect in the intake system after the MAF sensor that could be causing it. But to be honest i wouldn’t be surprised if you’re dealing with a wiring issue on this one as I’ve drove my fit with a massive leak past the maf without realizing it and never had an issue. Do you have a cheap scanner you can hook up to your car via the OBD2 port and see if the down stream sensor values are actually changing whole the car is running or if it is stuck in range?

 

I do have a cheap Bluetooth scanner and use an app on my phone for a scan. I will have to see if I can monitor the voltage while it’s running, thank you for that idea.

 

Sorry for the delayed response, been pretty busy.
Watching the voltage lets me see that the sensor is reading like it should for a while when driving, then all of a sudden it goes to 0V and stays there.

I went to Autozone to have them check the battery to rule that out, and the battery tested at 100%. They did read my codes also, and a couple popped up that my reader doesn't give me. They were 86-11 F-CAN bus-off malfunction and 61-11 Modulator-control unit power source circuit (IG) low voltage.
So I am thinking there may be a short somewhere, or a bad ground but have yet to have time to search for it.

Any other thoughts or ideas?
Thanks again.

 

Is your negative battery wire tight? Are your ground wires under the hood in good condition, making good contact? I would check that as it is very easy to do...

 

I keep getting the P0171 lean bank 1 code. I haven’t been able to find the cause.