kepani

moderators: please excuse this post if it's not in the right forum.

car: 2001 integra type-r - odbii
miles: 42,000 mi.
modifications: jdm length header, jdm oem cat., etc.

i have a question regarding the secondary oxygen sensor. i remember reading in a post some time ago about the secondary oxygen sensor not having any impact on the functionality of the motor.

i have been doing a lot of reading on o2 sensors (i'm new to fixing cars, etc.) and understand that the function of the primary oxygen sensor is to regulate air/fuel ratio by sensing o2 content in the exhaust gases at the outlet of the header pre-cat. i did also find that the secondary o2 sensor is used to determine if the catalytic converter is doing its deed; again by sensing the o2 content in the exhaust system post-cat. only this time, the ecu takes the voltage differential of the two o2 sensors.

i am running a jdm oem itr cat for my spoon exhaust system with my secondary o2 sensor ziptied to the shift linkage. apparently, the jdm cats don't have a bung for a secondary o2 sensor (that i am aware of?). i keep getting a cel (code 63: o2 sensor, high/low voltage, slow resp.). i keep resetting it by pulling the back-up radio fuse only to naturally have the cel come back up in a few days.

should i be worried about this code? is it simply telling me that the cat is not working properly? i'm just trying to be as cautious as possible and am hoping that the cel light is just a warning, not an indication that my motor is not running properly.

any help or comments would be greatly appreciated. thanks!

cliff notes: cel 63 secondary o2 sensor, is it just an indication of bad cat or something worse?

poison

Having the 2ndary O2 sensor code will not affect the engine's performance, however your ECU is running in open loop mode with the CEL going.

It's not something to worrya bout, but I would recommend either getting a US high flow cat with the O2 bung on it, or chipping/converting to OBD1 to get rid of that code.

HTH.

kepani

is that referring to open loop with regards to the primary o2 sensor? meaning, is my ecu not alternating fuel supply to regulate between lean and rich? :s if so, is my motor leaning on one side of the fuel delivery curve?

i have a jdm header exhaust system so i went with the oem jdm itr cat. am i right in saying that jdm cats don't have a secondary o2 bung?


i have heard of people wrapping the secondary o2 with tin foil. another idea is/was tricking secondary o2 into reading a set voltage. any ideas on this?

poison

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by kepani &raquo;</TD></TR><TR><TD CLASS="quote">is that referring to open loop with regards to the primary o2 sensor? meaning, is my ecu not alternating fuel supply to regulate between lean and rich? :s if so, is my motor leaning on one side of the fuel delivery curve?

i have a jdm header exhaust system so i went with the oem jdm itr cat. am i right in saying that jdm cats don't have a secondary o2 bung?


i have heard of people wrapping the secondary o2 with tin foil. another idea is/was tricking secondary o2 into reading a set voltage. any ideas on this?</TD></TR></TABLE>

Yes, I have seen the tin foil deal and have seen it to work. I would definitely try that.

Open loop mode is not bad, just has some wack air/fuel mixtures, and can bog on certain RPM's at certain times, and is a bitch to tune with.

Padawan

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by poison &raquo;</TD></TR><TR><TD CLASS="quote">however your ECU is running in open loop mode with the CEL going.
</TD></TR></TABLE>

Out of curiosity, do you have proof of this? It doesn't seem to make sense that the ECU would switch to open-loop because of a faulty/missing secondary 02. Still, ou may be correct, but that's why I was wondering what proof you had.

poison

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Padawan &raquo;</TD></TR><TR><TD CLASS="quote">

Out of curiosity, do you have proof of this? It doesn't seem to make sense that the ECU would switch to open-loop because of a faulty/missing secondary 02. Still, ou may be correct, but that's why I was wondering what proof you had. </TD></TR></TABLE>

Well with CEL's, and the ECU throwing a code, it effects the fuel mappings (not necessarily a lot), but is better to run in closed loop mode for performance/tuning wise.

Sometimes the engine will feel weak or bog at certain RPM's, or being the 2ndary O2 sensor, could affect mainly the emissions associated since the ECU -- and won't pass.

Just something to refer to..

Padawan

I'm aware that certain CEL conditions will cause the ECU to switch to open-loop. What I meant was, do you have any proof that a CEL due specifically to the secondary 02 will cause an open-loop condition? All information I've come across indicates that the ECU simply illuminates the CEL when the secondary 02 is faulty, and all other fuel/ignition settings remain unaffected.

Edit: Again, I could be wrong, but I haven't seen any proof to the contrary.

kepani

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Padawan &raquo;</TD></TR><TR><TD CLASS="quote">All information I've come across indicates that the ECU simply illuminates the CEL when the secondary 02 is faulty, and all other fuel/ignition settings remain unaffected.</TD></TR></TABLE>

this is what i've heard as well.

going back to the notion that the faulty secondary o2 sensor may cause an open loop situation, i did however notice better gas mileage. it may be a result of the new header/b-pipe/cat-back. maybe the computer was dumping less fuel.

i'm going to check out more of the obdii pages to see if this is indeed true.

poison

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Padawan &raquo;</TD></TR><TR><TD CLASS="quote">I'm aware that certain CEL conditions will cause the ECU to switch to open-loop. What I meant was, do you have any proof that a CEL due specifically to the secondary 02 will cause an open-loop condition? All information I've come across indicates that the ECU simply illuminates the CEL when the secondary 02 is faulty, and all other fuel/ignition settings remain unaffected.

Edit: Again, I could be wrong, but I haven't seen any proof to the contrary. </TD></TR></TABLE>

You might be confusing limp mode with open loop mode. limp mode disables vtec, retards the ignition timing, and ruch a lot richer, where as open loop runs just as normal, only disabling the sensor that it's supposed to get readings from (secondary o2 sensor -- if at all), and uses other sensors to operate normally.

If it's a required sensor (such as fuel injectors, MAP, etc.) that is a major sensor and will cause the ecu to go into limp mode which runs off the standard maps in order to operate an engine w/o blowing it up.

I don't think secondary o2 sensor has much effect on it, but I was stating it could cause him to run a little poorly, have issues with tuning the motor (if he does), and have effect emissions results (if he were to operate while trying to get emissions done).

WundedSaint

secondary o2 sensor doesn't affect fuel trim at all....it just there to tell you wether the cat is bad or not. THe ecu doesn't go into "limp home" mode just because the cat is bad. It'll just throw the check engine light but doesnn't affect performance at all. I'm a diagnostic technican btw...I've worked on all sorts of emission related problems. 80's cars are the weirdest cars and I think alot of people apply the same techniques of the 80's on obd2 cars...but in reality it's a whole different world.

Padawan

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by poison &raquo;</TD></TR><TR><TD CLASS="quote">You might be confusing limp mode with open loop mode. limp mode disables vtec, retards the ignition timing, and ruch a lot richer, where as open loop runs just as normal, only disabling the sensor that it's supposed to get readings from (secondary o2 sensor -- if at all), and uses other sensors to operate normally.</TD></TR></TABLE>

No, I understand the concept of open-loop. A normally functioning ECU will operate in open or closed-loop mode depending on throttle position. I think a better definition of open-loop is to say that the ECU ceases to adjust A/F based on the <U>primary</U> 02, and instead uses stored maps and values from other sensors (e.g. TPS, IAT, etc.) to control the mixture. "Open-loop" mode is actually employed quite often by the ECU.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by poison &raquo;</TD></TR><TR><TD CLASS="quote">I don't think secondary o2 sensor has much effect on it, but I was stating it could cause him to run a little poorly, have issues with tuning the motor (if he does), and have effect emissions results (if he were to operate while trying to get emissions done).</TD></TR></TABLE>

The secondary 02 is used to determine catalyst effectiveness, so it shouldn't have any effect on closed-loop mode (again, I'm open to anyone providing proof otherwise). Most tuning is done while the ECU is in open-loop anyway, so even in the off-chance that the ECU was forced into a constant open-loop mode (which would mainly affect idle and very light throttle conditions) there shouldn't be any problems with tuning.

kepani

thanks for the helpful info padawan, poison, wundedsaint! i am that much more educated on my car. i guess i'll just have to deal with the cel, or just keep pulling the back-up radio fuse. down the road, i'll try the tin foil trick.

as for the open/closed loop discussion, this is good stuff!

poison

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Padawan &raquo;</TD></TR><TR><TD CLASS="quote">

No, I understand the concept of open-loop. A normally functioning ECU will operate in open or closed-loop mode depending on throttle position. I think a better definition of open-loop is to say that the ECU ceases to adjust A/F based on the <U>primary</U> 02, and instead uses stored maps and values from other sensors (e.g. TPS, IAT, etc.) to control the mixture. "Open-loop" mode is actually employed quite often by the ECU.</TD></TR></TABLE>

Yea I understand A/F mappings based on the primary O2 sensor. I just wasn't 100% positive about the secondary O2 sensor, based on what I`ve seen (mainly emissions, not just performance tuning).

Other than that, very informative and I stand corrected if I am wrong.

d16civicex

so would it be ok to drive on a 3 hours trip with a bad 02 sensor?

kepani

assuming you're referring to the secondary, it would not be a problem.

* one caveat to that would be that if you're in california (i see you're in pa) and were for some reason pulled over and the officer saw your cel illuminated, he could summon your car to a referee for a check. the conclusion is that the secondary o2 sensor is simply an indicator that your catalytic converter is not removing all of the pollutants effectively.

other than that, you should be fine.

d16civicex

sorry i was referring to the primary, i forgot to say that

kepani

if it's the primary, then that is not good. i'll try and give my best answer, though others should chime in if what i'm saying is not correct.

the primary will regulate fuel flow rate based on oxygen content in the combustion gases as they leave the header. when the o2 level is at one end of the spectrum (high, low), the fuel delivery is adjusted accordingly. but if the primary is not registering, there is a chance for the system to either dump too little or too much fuel into the chambers. i'm not sure of what else can happen, but either way, it would be good to get it replaced asap.

hope that helps.

stolibears

some really good information about the o2 sensor here. after putting my hi flow cat my engine light came on after about 10 miles. i've heard a lot of second hand info on whether to worry about it or not. I choose not to and have had the cat on for about 3000 miles and no problems so far. i don't have any major mods yet, just air intake and exhaust to have to worry if maybe engine light might actually be something else wrong with the engine instead just the o2 sensor having a fit. another thing you could do kepani is take the bulb out of the dash for the engine light so it isn't so annoying, unless of course you have made some engine mods. i've heard chipping out the ECU is the really only sure way to make sure that you get better feed back from your ecu and sensors with the type of mods you already have. and no pesky engine light crying about the o2 sensor.

as far as performance, i have had a lot fun with the new cat. a noticeable difference in acceleration. I too noticed better gas mileage, but also wonder if it has to do with better breathing from the new intake, cat and exhaust or something to do with the o2 sensor, or possible the combination of both by the way the ECU may be interpreting how to the air/fuel should be made since more air is moving.

let us know how the tin foil trick works out when you get a chance.

thanks guys

stolibears

to clear up confusion, I was talking about the 2nd o2 sensor not the 1st. big difference.