kbw2000civicex

Is this a must replace item. Like a fool I damaged it trying to remove it. My converter is rattling from the inside so I removed it and damaged the sensor. Put it all back together and check engine light is on. The damage came when I tried to unplug the wires from the sensor INSTEAD of disconnecting the clip behind the boot. I can live with the engine light but if this sensor does more than checking the catylitic converter for emisions then i must replace. I don't have a problem with buying a new sensor but theres like 10 to choose from ranging from 230 to 40.
Thanks.

HitF8

it might make your car run a little funny. i would replace it.

MilanoRedEk99

Yeah I would replace it If I were you.

kbw2000civicex

What does the O2 sensor in the catylitic converter sense? There is another sensor just before it in the manifold.
What will happen if I do not replace.
I was going to watch my fuel mpg
i was getting 33mpg
Thanks

EJ8_Enthusiast

MANY will say the rear o2 does absolutely nothing.

It tells your car how well the cat is working, that's it from what I understand.

I fixed my o2 issue and I get the same mileage and the car runs the same so I do not think it matters, just a CEL.

wrenchez81

if your talking about the downstream sensor ...the o2 sensor in the cat simply measures the oxygen flow through the exhaust..... UNLIKE THE UPSTREAM IT IS ONLY A MONITOR AND HAS TEE TEE TO DO WITH DRIVEABILITY!! what happens my friend is this..... when the ecu sees both sensors swinging in time with one another it then knows the catalst in your converter has deteriorated and will throw a code po420 catalyst below threshold.... if you damage the sensor physically than more than likely youll set a circuit code.... if its the upstream youll go into foced open loop and be running pretty rich....

kbw2000civicex

awesome avitar Wrench!
Thats what I wanted to hear.
I'm going to throw a universal catylitic converter on without the sensor port and then figure out a way to keep the ecu happy.

wrenchez81

anytime friend!!! to trick the ecu you need to get an emulator.. these have been outlawed and moreso becoming difficult to find ... i think theres a diy o2 sensor emulator with some resistors you can find @ radio shack.. i was told this by another tech that successfully done so..

jolt-tsp

The only thing it may affect is your ability to pass emissions depending on your county.

kbw2000civicex

I figured i broke my sensor when trying to unplug it. I couldn't unplug so i snipped the 4 wires. Well after i put it back in and soldered the wires back the check engine light came on. So i switched the 2 blacks and tried again. Same thing light still on. I just now unhooked battery for 10 minutes and the light cleared. Maybe i never ruined it after all. time will tell.
still have that faint rattle after ten minutes of driving coming from inside the cat converter when first accelerating. Its not the heat shield. I swear its coming from inside the cat. conv.

EJ1 LS guy

umm not sure about this but when I did my swap I didn't put the 02 sensor on my cat so when I start my car it did a weird idling noise.....like jumping to 3000k then dropping to 900k.....repeatedly.......until it warmed all the way up......and that's the only code I throw.....is this the same problem....and how do you fix it???.........

honda.lioness

Some O2 sensors located after the cat converter do adjust the fuel trim slightly. See http://temp.corvetteforum.net/...c.pdf (page 10, near the bottom) and the discussion with citations at http://www.hondacarforum.com/h...20168 . But it appears the 96-2000 Civic's secondary O2 sensor ( = the one post cat converter) does not. From http://www.autozone.com/shoppi...8f5c9:
"The [secondary oxygen] sensor mounted in the exhaust system after the catalytic converter is not used to affect air/fuel mixture. It is used solely to monitor the catalytic converter and [primary] O2 sensor efficiency."


Modified by honda.lioness at 12:52 PM 11/5/2008

wrenchez81

^^ this is not true.... every manufact. is the same THE DOWNSTREAM IS A MONITOR ONLY!!! irepeat THE DOWNSTREAM IS A MONITOR ONLY!!! the only time a secondary o2 sensor would have an effect like on a corvette is if the engine has two banks in which it has 2 upstream sensors!!!


Modified by wrenchez81 at 1:03 PM 11/5/2008

EJ1 LS guy

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by wrenchez81 &raquo;</TD></TR><TR><TD CLASS="quote">^^ this may be true.... but NOT ON A HONDA sweetheart!!!</TD></TR></TABLE>

yeah I was kinda lost anyway......I kinda just wanna know whether or not I should stick it it my cat or make a hole in my piping......to stop the idling problem and get rid of the cel....

wrenchez81

the cat has nothing to do with your problem,, in fact if it was completly clogged the car wouldn't be able to go over 20mph and it would take a year to get there... pm me your symtoms and ill see if i can help!!

EJ1 LS guy

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by wrenchez81 &raquo;</TD></TR><TR><TD CLASS="quote">the cat has nothing to do with your problem,, in fact if it was completly clogged the car wouldn't be able to go over 20mph and it would take a year to get there... pm me your symtoms and ill see if i can help!! </TD></TR></TABLE>

pm'd

honda.lioness

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by wrenchez81 &raquo;</TD></TR><TR><TD CLASS="quote">every manufact. is the same THE DOWNSTREAM IS A MONITOR ONLY!!! </TD></TR></TABLE>

The citations I gave say otherwise and for makes other than the Corvette.

wrenchez81

im not here to argue... just help... i know this is gonna sound really really stupid!! i cant find anywhere that lets you access pm's on this forum.. does anybody know were that beeyoch is?? and by the way ,, obd2 started the use of catalyst monitoring which incorperated the use of a downstream sensor... if that was the case don't you think that pre obd2 cars would have a downstream sensor aswell??

EJ1 LS guy

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by wrenchez81 &raquo;</TD></TR><TR><TD CLASS="quote">im not here to argue... just help... i know this is gonna sound really really stupid!! i cant find anywhere that lets you access pm's on this forum.. does anybody know were that beeyoch is?? and by the way ,, obd2 started the use of catalyst monitoring which incorperated the use of a downstream sensor... if that was the case don't you think that pre obd2 cars would have a downstream sensor aswell??</TD></TR></TABLE>

you go to my profile.......then click on instant message history.......then click on save to notepad by the name your trying to read the stuff from.....an click open Im to write back.......thats how I do it.....lol

wrenchez81

teeeeeeeeeeeeeeeen foe!! thanks man!!

honda.lioness

Other documents supporting the manual's statements quoted above:

1.
"The front heated oxygen sensor is used by the Powertrain Control Module (PCM) to sense exhaust oxygen content and control fuel trim. The rear heated oxygen sensor reports the exhaust oxygen content after the catalytic converter to the PCM. The PCM will also use this information to determine catalytic converter efficiency. If the voltage level of the rear heated oxygen sensor stays above or below a 450 millivolt level for an extended period of time, the PCM uses this information to make slight fuel trim adjustments." See page 3, http://www.wellsmfgcorp.com/pd...2.pdf

2.
From a 2004 Subaru Impreza manual:
"The air/fuel (A/F) control system makes a correction to the basic fuel injection duration in accordance with the signals from the front oxygen (A/F) sensor and the rear oxygen sensor so that the stoichiometric ratio is maintained... "
http://ken-gilbert.com/wrx/STi...m.pdf

3.
From a 90s Nissan manual:
"On some models, a rear oxygen sensor is located downstream of the three-way catalyst. Even if the switching characteristics of the front oxygen sensor shift, the air/fuel ratio is controlled to stoichiometric by the rear oxygen sensor."
http://www.autozone.com/az/cds...s.htm


Modified by honda.lioness at 3:36 PM 11/5/2008

wrenchez81

believe what you want!! you can keep posting till your eyes turn blue!!!! ive been in this field since i was in diapers,, took three years of tech school, took the CARB/EPA california based emission exam and class (18 months). reading can be fundamental!! if your reading the proper information... no offense but autozone is the equivalent to a nurse and me chica am equivalent to a surgeon!!! read read and read again.........

honda.lioness

No problem except for one caveat: For any given car model, Autozone's free online manual is an excerpt from the model's factory service manual.

wrenchez81

ok how about this.. im gonna do a little project just for you. I have at my disposal many thounds of dollars worth of testing equipment.. one in particular which is made by Launch is called a crecorder. this allows me to upload vehicle information over a period of time... kinda like a black box.... and what im gonna do is graph fuel trims over a period if time in both modes with and without a failed or open circuit downstream o2 sensor and show you it makes absolutley no difference what so ever ... okay so just stay tuned... i work 60hrs/6days a week twisting wrenches so it may take a bit.....

EJ8_Enthusiast

wrench - if you do that, please post it in a thread on its own so it can be referenced from the faq, people ask this damn question at least weekly and people always argue.

I am with you on this one, it makes no difference on or off.