TeamEK

Whats the difference between Primary & secondary o2 sensors? And can someone tell me what happens if you have a bad o2?

nsxter

Primary = first , secondary = second lol

cehcivic15

hey there are a few really good explanations of it on youtube, just search for oxygen sensor

96hb

The only thing I know about O2 sensors is that they are expensive as hell. I would replace mine if they didn't cost a small fortune. Every once in awhile I will get a CEL for this and I will just reset it. The funny thing is my car still gets great mileage and runs fine.

RareSpirits

before and after cat, one reads emissions before, and the other after!

TunerN00b

To be a bit more specific.

The primary is looking at how the engine is running, so that the computer can adjust fuel as needed for correct operation.

The secondary is just to verify that the cat is still working correctly, but nothing more.

Red_Army

^^right there be your best answer.

1st- engine performance checker
2nd- cat checker so you know when to replace it because emissions is getting heavy.

titi_vtec

if you have one of then not working you going to consume more gas, but it is not a big difference, but they are different between then

TeamEK

Aright, because what i did was i the brought a new primary and put the old one in the secondary, so i could save money,

but is both o2 bulit or functions the same?

Red_Army

i know on some cars they are different. but idk if they are on hondas.

TunerN00b

Have the Honda dealer check the part numbers of each. If same part for both, sounds like you did the right thing. If not, you might get a CEL for the 2nd one being the wrong part.

The primary is the one you need to be concerned with for running right and getting good mileage. The 2nd is literally just a cat check, and is only there because the law mandates it, and won't cause any issues with the car.

Actually, even if you do get a CEL, you can try putting the old secondary back in there on a spark plug anti-fouler, reset the CEL, and see if it comes back.

BryanM.

iTrader: (1)

I am using a primary 02 sensor as a secondary. On top of that it's from an OBD1 car.

Most FI cars use "standard" 02 sensor(s), 4-wire, with a 18mm x 1.25 threaded end.

VX/HX Civics do use a wideband primary 02 sensor, don't know if that will work as a secondary.

.

TeamEK

Yeah rite now both o2 are primary, the new one on top and the old one at bottom of my car. Yes the CEL did come on a couple of times but i restarted it. My CEL read
1 O2A - Oxygen sensor #1
2 O2B - Oxygen sensor #2
3 MAP - manifold absolute pressure sensor
4 CKP - crank position sensor

I think i need to replace the old one, but one last question, dose a bad o2 affect air flow coming out your exhaust?