HELLO, new to site, would appreciate some assistance! P0139

how cool is this a site for DTC's

look forward to hopefully solving a few problems! first one is for my 05 Civic. 1.7 L SOHC 5spd Sedan.

mods: AEM Cold air - short ram
Eibach Pro Kit
Tint

Mileage: about 40,000 miles
Problem: poor gas mileage
Actions: brand new Bosch O2 sensor, to go with Bosch Plat +4's mileage came back for 1 day, then i swapped in the NKG Plugs, great for one day then s**t since then. down from 42 mpg on average to 30... wtf!

Root Cause: I am lost at this point

code specifically reads " P0139 O2 Sensor CKT slow reponse Bank 1 Sensor 2"

it is an inline 4 cylinder, so I would interperet that as only 1 Bank, I replaced the O2 before the cat. Do I need to replace the O2 after the cat? I don't understand the car ran great for 2 days with the new O2 then crapfor the last day and a half, with no change in site, lol!!!

what to check next?

If you changed the O2 sensor before the cat, then you changed the wrong one. Check the circuits with a dvom, make sure the connector is not damaged.

thanks for the reply, is there anyway to know if it is the samepart as the front o2, that means i have an extra good o2, lol!!!!

i figured that out after doing some more digging late last night, i will get this fixed asap! i miss 40 plus mpg.

DVOM = digi volt meter i am assuming? what steps can i take to verify functionality.

thanks
taner

99% of the time they are not the same, nice try though!

thanks! a direct fit is 270 bones ! ouch! a universal is 79 bux. universal it is! lol

i will be picking the o2 up tomorrow, funny thing is if i rset the pcm i get great mpg for about 400 km and then it starts to get shitty, lol!!!

fuel economy is kickin' but again!
averaging city and highway, just over 41 mpg! i love this little car again!

congrats