Hello! I have a 2007 Honda Fit that I am currently experiencing a headache with. Issue started a couple weeks after I got it, engine code p0420 code was popping and throwing the car into limp mode, but only after about 40-50 minutes of driving. Inspected cat, cat was indeed getting clogged, and replaced with new one, I didn't do this job, the shop I got it from did it for me, so I am unsure if the downstream 02 sensor got replaced with it (although visibly it looks cleaner) This did great for about a week and a half, and my light popped on again, this time p0135. Not acquainted by any other codes. Did as much research as I could to diag, and ended up doing this list of things
-Replaced upstream 02 sensor with Rock Auto replacement.
-Did some googling, found something that hinted at temp sensor 1, tested with new part.
-Inspected/tested temp sensor 2 (bottom of radiator) did not replace as it seemed fine.
-Noticed the engine code comes on almost instantly after clearing now
-Checked all fuses, and made sure power is getting to the harness itself, and all fuses
-Noticed the harness side of the connecter gets power/ground ONLY when not connected to 02 sensor as well. As soon as it gets plugged in, no more power.
-Last thing I did today, after straining my brain on it for four hours, is take it to my shop again, and the owner said he has a suspicion of a potential bad throttle body, caused from backpressure of clogged cat initially.
If someone could save my brain cells from hurting you would be a life savor.
P.S. I'm proud I even got this far, only experience is from working at a junk yard and working on my previous Altima.
Thank you

 

Hey there. Had that code come up a while back on a 2008 Fit.
DTC P0135: A/F Sensor (Sensor 1) Heater Circuit Malfunction.
In that particular instance I wound up replacing a faulty A/F sensor relay.
The attached pages cover troubleshooting, testing the relay and replacing the sensor.
Hope it helps.

 

Good morning, I work at a junkyard, so to test my a/f sensors/relays I grabbed spares from a fit out in my yard (same make model trim) and it was to no avail. I must have tried 3-4 different relays. I do thank you however since now I can troubleshoot wiring, since that is the only remaining possibility to the sounds of it. On a side note, where did you get that book from? couldn't find anything in the manual... maybe I didn't look hard enough.

 

2007-2008 Service Manual
Keep us posted on your troubleshooting efforts.

 

Is your Fit running the latest ECU update per the Honda 10-015 TSB?

 

Sorry for late updates, I ended up contacting the shop I bought the car from and they were willing to give it a go, so that is where the car is. I will keep posted for what he finds out. Thank you all again.