O2 sensor secondary

[Drift King]

My engine light has come on a lot of times saying its my cat, but would always go away. Recently its been on continually and has also added a code for the secondary O2 sensor. When I got my timing belt replaced at the dealer he said the O2 is about 300 to replace and the cat was covered. My thinking is that the O2 isnt bad, the computer just says that because the cat code comes on so much. Unfortunately the dealer cant get the cat for 3 days, because its such an incredibly rare part, so I have to schedule another appointment for them just to replace the cat. Any ideas on what to do with the O2. Keep in mind Im a broke college student.

[CivicSpoon]

Why would your cat be rare? And what do you mean by "My engine light has come on a lot of times saying its my cat", do you mean it come up with the primary O2 sensor code? If it is your cat that is bad, it can cause your O2 sensor to go bad as well.

[Drift King]

I was being sarcastic about being rare. The light would always come on and I ran the code, just the cat code, the light goes off, comes on a month later, ect. Eventually the code for the O2 came on as well. I guess the cat killed it, but how can it do that?

[superbluecivicsi]

because if your catalyst efficiency is below threshold. it means all that pollutant junk has clogged your cat. your o2 sensor is plugged in there too. thats why it will crap too.

go pick up a universal denso o2 sensor off ebay and take your cat in to be replaced if it is covered under warranty. when the cat is in, replace the o2 sensor yourself.

just curious, what car is this?

[Drift King]

This is a 98 civic. Good plan, I've already lined up the cat replacement. How simple is switching the O2? Would you be able to tell me how to do it?

[superbluecivicsi]

Originally Posted by Drift King

This is a 98 civic. Good plan, I've already lined up the cat replacement. How simple is switching the O2? Would you be able to tell me how to do it?

a 22mm wrench and a junction plug. i bet my 8 year old newphew could do it.

[Smoghog]

Originally Posted by Drift King

This is a 98 civic. Good plan, I've already lined up the cat replacement. How simple is switching the O2? Would you be able to tell me how to do it?

Hey Driftking, Just a side note. First your car has two ho2s (heated o2 sensors) one before the cat, one after.

I would check your cat first before you repl it, being it's a 98 it should still be good if you haven't been abusing it too much. or ran too long with the CEL light on

The reason you are getting the cat code is the second o2 is reading a fluxsating o2 reading. This could be because the first o2 has slowed or is baised rich or lean and your cat isn't working right (not storing enough o2)

Have you checked the output of the ho2s? You will need a ocilloscope
to check them. They operate to fast for a normal DVOM

I would check them first before you put on the new cat, as if you don't the new cat will end up like the one you allready have, if it is actully bad

Sorry for the spelling errors I don't feel like looking them up

Smoghog

[superbluecivicsi]

ill make it simple for you.

reset the ecu. if the cel comes back as catalyst effeciency and secondary o2, then they are both gone.

youwant to physically check the cat and o2 sensor? drop out the cat and look through it. if you can barely see anything or nothing at all, then it is gone.

Have you checked the output of the ho2s? You will need a ocilloscope

this isnt your high school science lab. simplicity = go get a cheap and simple voltage and continuity meter from walmart, kmart, walgreens, or riteaid. measure and compare to specs.

The reason you are getting the cat code is the second o2 is reading a fluxsating o2 reading. This could be because the first o2 has slowed or is baised rich or lean and your cat isn't working right (not storing enough o2)

actually, there are many reasons as to why the cat will go bad and get clogged. i believe whatyou are trying to say here is that the primary o2 sensor can go bad and throw a cel (problem here is, there is no cel for primaryo2 sensor )causing the ecu to go into open loop mode, causing the car to throw in more fuel to keep things safe. throwing more fuel and possibly not burning all of it may increase the the amount of N2, CO2, CO, other hydrocarbons, blah blah blah. basically the cat has to work harder meaning there is not enough stuff in the cat to keep up with the pace.

im getting tired of typing, so ill make it short.

there is a reason why your cat is gone.

not storing enough o2

the cat does not store o2. o2 is part of the product of the conversion process in the cat. the o2 sensor just reads it.

[Smoghog]

Originally Posted by superbluecivicsi

ill make it simple for you.

reset the ecu. if the cel comes back as catalyst effeciency and secondary o2, then they are both gone.

youwant to physically check the cat and o2 sensor? drop out the cat and look through it. if you can barely see anything or nothing at all, then it is gone.



this isnt your high school science lab. simplicity = go get a cheap and simple voltage and continuity meter from walmart, kmart, walgreens, or riteaid. measure and compare to specs.



actually, there are many reasons as to why the cat will go bad and get clogged. i believe whatyou are trying to say here is that the primary o2 sensor can go bad and throw a cel (problem here is, there is no cel for primaryo2 sensor )causing the ecu to go into open loop mode, causing the car to throw in more fuel to keep things safe. throwing more fuel and possibly not burning all of it may increase the the amount of N2, CO2, CO, other hydrocarbons, blah blah blah. basically the cat has to work harder meaning there is not enough stuff in the cat to keep up with the pace.

im getting tired of typing, so ill make it short.

there is a reason why your cat is gone.



the cat does not store o2. o2 is part of the product of the conversion process in the cat. the o2 sensor just reads it.

Not to argue but the o2 voltage fluxuates to fast for a "normal" DVOM
So you will not get the readings/spec's you are looking for.

And, o2 is stored in the cat just for a little bit. For a correctly working cat to work, and last it needs to switch between rich and lean. lean to store o2 to burn when rich. I admit I don't know what codes are for what for your car. Is there really a code for the cat? and if there is it is set from the downstream o2 sensor.

That is just how it should work.

SH

[CivicSpoon]

Yeah I didn't know there was really a code for the cat either, until I looked it up for this thread. It's the "Catalyst System Efficiency Below Threshold" code (I believe).

[Drift King]

Ok, I've had the cat replaced so I'm trying to buy the O2 sensor fast. Im just looking for the cheapest thing but I'm not sure what that'll be. I see bosch, denso and no-name on E-bay. Wondering if someone could give me a link to something, I have a 98 civic EX. Sorry for all the trouble guys but thanks for helpin me out.

[Smoghog]

Originally Posted by Drift King

Ok, I've had the cat replaced so I'm trying to buy the O2 sensor fast. Im just looking for the cheapest thing but I'm not sure what that'll be. I see bosch, denso and no-name on E-bay. Wondering if someone could give me a link to something, I have a 98 civic EX. Sorry for all the trouble guys but thanks for helpin me out.

I would say, stick with a name brand. I've heard of O2 sensors working for a week then dying.

Be careful not to drop it either.

SH

[superbluecivicsi]

ebay universal denso 4 wire off ebay for $35. still working for 2+ years.

[Drift King]

OK. Got it superblue. Last problem, do you remember what wires were which on the OEM plug? This one came with a chart saying this color goes to that color ect, but I cant see how it can be the same for all cars. I guess I need to know the ground, heater power 1 & 2?, and signal wires.

[superbluecivicsi]

dont remember. this is 4 wire? what does instruction say? color on new sensor? colors on old harness?