As some of you know I had a deteriorated primary O2 sensor recently, supposedly as a result of the Mugen header install. (see thread https://honda-tech.com/zerothread?id=436638)
Anyways I went to Honda this morning and had them confirm code 61 which is a deteriorated Primary O2 sensor. It was confirmed, I knew it all along that I the O2 sensor was fried. So I found a junkyard that had a Prelude Primary O2 sensor, but as I was on my way to get I got to thinking how ncessary is an O2 sensor. I know the function of an Os sensor it to control emissions and make a car run more cleaner (efficiently.) The questions I want answered are
-->If one does the NTPOG work around with reseting the ECU everytime the car is turned off how does this affect the A/F ratio? Because I might as well pull my 7.5 fuse (radio/clock fuse) and run the car like that all the time if the A/F ratio isn't affect, BUT I THINK IT IS.
-->How does the VAFC over ride the O2 sensors? More specifically if the O2 sensor's job is to monitor A/F ratios and adjust accordingly to run the car efficiently, then how can the VAFC tell the engine it want's a specific A/F ratio?, and have it stay and that specified A/F ratio. And yes I know its a "Piggy-back" fuel system. (not the best in the world.)

Oh BTW Honda raped me for $47.48 for 10 minutes for of pulling a ******* code that I alreadt knew and told them that I knew just want them to consider any other possible solution the the problem before I bought a knew O2 sensor.
I'm and for letting Honda do that ****.
And they make me

So let's pull together all the great minds of HT and solve this, as its a problem and if not a problem its a consideration among many at HT.
ODBII

 

I don't think your car will run without a primary o2 sensor...

 

The primary O2 sensor is required by the ecu. It doesn't monitor a/f, it detects the oxygen content in the exhaust and signals the ecu accordingly. The ecu receives the signals from the sensor and varies the duration during which fuel is injected. This is called closed loop operation, during which the ecu tries to keep the voltage from the O2 sensor around .5V. The system is designed so that .5V is about "stoich" (14.7:1). During WOT, the ecu ignores the O2 signal and runs in open loop on a preprogrammed map to keep the engine running rich. If the O2 sensor is removed, both codes 1 (open in primary O2 sensor circuit) and 41 (open in primary O2 sensor heater circuit) will be thrown, and the engine will run in open loop.
Resetting the ecu returns the ecu to using factory presets for fuel and ignition, rather than using memories based on long term driving habits. How much does it really affect how the ecu runs the engine? I think the better question is how well does the memory system really work. I have the OBDII workaround and a wideband on my car, and as soon as the engine is warmed up the a/f numbers hover very closely around 14.7:1 at idle and part throttle off boost. So either the ecu learns very quickly, or the memory function (and therefore the OBDII workaround) is rather useless. I'm only using the workaround because my egr is blocked by my hondata gasket.
It doesn't. The VAFC has nothing to do with the primary O2 sensor. The ecu does not solely rely on the primary O2 sensor input in its decisions regarding fuel and ignition. It uses the MAP sensor, the ECT sensor, the IAT sensor, the TP sensor, and probably a few other things that I'm missing. The primary O2 sensor is just one input the ecu considers. The VAFC works by modifying the MAP sensor signal so as to fool the ecu into adding or subtracting fuel.
Again, the ecu doesn't know anything about a/f, it only knows that it wants the primary O2 sensor, in closed loop operation, to be about .5V. The VAFC doesn't tell the ecu anything accept a false MAP sensor voltage, which in turn causes the ecu to be fooled into thinking it needs to add or subtract fuel.

 

As far as I know, the ECU uses the O2 sensors for normal driving, but at WOT and when the engine is being loaded, it ignores them and goes to a look-up table basing its decidion on various inputs (which V-AFC modifies, if you have it installed). That's all I know.

 

The system will revert back to it's base map and start logging again to attempt to have the car run more efficiently. Since you're resetting it every time however, you'll always be on the base map. Your A/F doesn't change much since it's always running the same base fuel/timing map.

The V-AFC doesn't override the O2 sensors. It doesn't do anything to them. It modifies the fuel map slightly and eventually the OBDII system will override some of the V-AFC's effectiveness by retuning the fuel back in. However, the VTEC transition will stay the same since OBDII can't do anything about that and you'll keep the best benifit of the V-AFC, a larger midrange. This was the logic behind the NTPOG workaround, tune on the base map and reset it back to the base map every time. You'll keep your A/F ratio since the ECU can't learn enough to retune.

My guess is that your O2 sensor is either spiked or low which is why it's reading a failure. You could possibly wire a resistor in it's place, but with no reading, the car will not work. Lastly, OBDII may be annoying for performance but go read up on OBDIII. You'll bless OBDII.

 

Thanks for the replies so far; I have to go to work but look forward to reading them when I get home!

 

heres the down low. you car can run without an o2 sensor. alot of people do it. its just a matter of if you want to do it or not.
o2 sensors detect if your car is running rich or lean and adjusts acordingly. without your o2 sensor you could be running too rich. which means lower gas milage, hotter exgaust gases which could cause your catalytic converter to burn out, and running rich could affect your valves in the long run.
so, is it worth all this just to save $250-$300????

driving your car with the check engine light on doesnt really matter either. as long as you know what the code is... and as long as the light isnt flashing. when you reset the car, chances are when you start the car up your computer already detects that the o2 sensor isnt working.
the light for the o2 sensor only comes on when the ecu detects no signal coming from the sensor. so, its like your driving without an o2 sensor in your car anyways... why keep reseting the ecu?

 

[ QUOTE
It doesn't. The VAFC has nothing to do with the primary O2 sensor. The ecu does not solely rely on the primary O2 sensor input in its decisions regarding fuel and ignition. It uses the MAP sensor, the ECT sensor, the IAT sensor, the TP sensor, and probably a few other things that I'm missing. The primary O2 sensor is just one input the ecu considers. The VAFC works by modifying the MAP sensor signal so as to fool the ecu into adding or subtracting fuel.
More specifically if the O2 sensor's job is to monitor A/F ratios and adjust accordingly to run the car efficiently, then how can the VAFC tell the engine it want's a specific A/F ratio?
QUOTE]

Dude, you forgot all about the TPS report


[Modified by 714, 1:20 AM 3/14/2003]

 

Bwahahahahahaha

 

Yeah, I'm replacing my primary O2 sensor today because I'm tired of resetting the code! Stupid freakin slow responding O2 sensor!!!

It's bad enough just getting the CEL, but since I have an SH, it automatically gives me the ATTS light too! Now I have pretty yellow lights on both sides of my gauges while I'm driving! Woo Hoo, It's balanced for my driving pleasure!

After spending a couple hundred bucks on a new sensor, I better not see this code again...wait a minute, I have a secondary that could go out too. Oh Joy! Thank you Lord...Thank you because I was worried about all that interest I was accumulating on my savings account and how it would affect my taxes! Praise to you for putting my mind at ease!

I'm sorry if I've offended any religious wackos, seriously. Please know that I myself am a Pedestrian in good standing at my local church, St. Handup- Our Blessed Lady of the Crosswalk.


[Modified by jji106, 3:58 AM 3/14/2003]

 

ok the computer is looking for a signal, which it uses to adjust POT. My guess is either it's not going to work, or not work long w/o the O2 in there. the O2 does measure A/F by monitoring the amount of oxygen in the exhaust (unlike quoted above where they said it didn't monitor A/F, because measuring hte Oxygen level is doing just that). The 2ndary just monitors the performance of the cat, which isn't really needed. That's my 2 cents anyhow.

 

No, it doesn't measure a/f. It produces a voltage based on the amount of O2 present in the exhaust stream. To say that it measures a/f infers that it detects both O2 and fuel, which it does not. Neither the O2 sensor nor the ecu know anything about a/f. The O2 sensor sends a voltage, the ecu receives it, and that is it. Nowhere in the process is this voltage converted to an a/f value.

 

I got aused O2 sensor form a junk yard yesterday I'm going to install it today and see if it still works. I made sure with the guy who sold it to me that I could return it if it doesn't work.

 

Yes, it measures the Oxygen, which it doesn't know. the CPU already knows the fuel. So by using hte Oxygen content rating in the exhaust that's left over from the combustion cycle, based on how much gas it used, it knows what hte A/F is, and how to adjust it to keep it running too lean or too rich, to keep emmisions good (and my guess is to keep things in check too). It does the same thing an A/F meter tagged off of the O2 sensor does. the amount of oxygen present lets it know if it's too lean or too rich.


[Modified by rjr162, 5:31 PM 3/14/2003]

 

All an a/f meter is doing is lighting up a colored light in a row of lights, and which light it lights up is based on the voltage output of the O2 sensor. All the ecu is doing is considering how much fuel to add or subtract based on that same voltage, and the ecu acts accordingly to keep the voltage at .5V. You interpret this as the ecu thinking it knows anything about what the a/f ratio is, which it does not.

 

it's not as simple as you are trying to make it out to be. It's just like an eletronic thermometer... the unit doesn't know the actual temp. It gets a voltage from a sensor that changes as the temp changes. the programming inside converts that to a temp based on a look up chart.... this is how hte ECU and O2 work.

 

That's exactly what I have said now, twice. You, however, were saying:
which is not true.


[Modified by sharkcohen, 10:58 PM 3/14/2003]

 

wow, you guys are going to town on this post.... he said he was going to replace the o2 sensor didnt he?

lets all celebrate because we told him what to do... and hes listening! this ones on the house.... next round is on you.

 

LOL, a toast for a useful thread

 

Ok so I got the used O2 sensor installed yesterday and no check engine light. But today I got the same code.
Here's exactly what I did yesterday.
-Jacked up my car, put jack stand under it.
-Took the negative cable off, and the 7.5 fuse out.
-Took out the old O2 sensor
-Screwed the new one in tightened it as best I could (there's wasn't a lot of room to work with.)
-Plugged the silly thing in, attached the wire to the clips.
-Removed the jack stands, lowered my car.
-Put the negatice cable and fuse back
-Started the car up, no check engine light, to make sure the ECU was reset properly I kept a constant RPM of 3000 until the cooling fan came on, then drove it around at differently speeds, and different throttle positions. AND no check engine light. GREAT.
-Drove the car to work yesterday and no check engine light
-Drove the car home from work and no check engine light.
SUNDAY
-Decided to go for a drive just to see if I solved the problem.
-AND guess what the check engine light came on once the engine got to temperature.
-Checked the code, and guess what CODE 61 again.
Seriously what in the world is going on. My only other guess could be, I have an exhaust leak between the exhaust manifold and the a-pipe, the O2 sensor isn't tight enough, an exhasut leak in between the a-pipe and the cat.
I question the exhaust leak because the manual states that exhaust leaks could also throw that code.

 

If you have a hole in the exaust before the O2 sensor, that will cause your problem. That would let oxygen into the exhaust giving a false lean reading from the O2.

 

It is possible that you have a leak between the primaries and the head or the primaries and the A pipe. You should double check to make sure that the lock nuts up at the head for the primaries are tightened to spec, and also double check the mounting hardware at the flange between the primaries and the A pipe. Those should always be double checked shortly after a header is installed and heated up a few times, anyway, as they can come loose.

 

Ok I checked all of the nuts, they are all tight I even tightened some of them some more. There is no exhaust sute on the a-pipe flang or on the cat flang. So I really don't think I have an exhaust leak. One of my buddies offered the idea that my O2 sensor problem could be the result of larger collector size.

 

I have a 2.5" collector on my Kami header. When I first installed the header, I was getting code 61 every few days. Then once a week. Now I don't get it at all. I never figured out why, and I haven't got it for a few months now.

 

Wait OBDIII??? holy cow!

well I get an intermittent CEL..it seems to appear ~500 miles after an oil change...i dont know what the code is cuz I dont know how to get the code...but now i do...and I think its cuz I have an exhaust leak...i was lookin under the car one day and it was cold out and I noticed the vapor from the exhaust was coming from the rear part of my high-flow cat where it bolts up to my evo cat-back....so it could be that..but then again it just came on today and I reset my ECU 2 weeks ago and it could be cuz of my TEINS that i just installed..but I doubt it..I have an SH..

also, is it true that you can get the CEL code when you turn the key to the auxiliary(where all the pretty lights are on on the dash but the engine is not on)position...my CEL flashed once...and I know thats probally not the way to check it but I looked at the CEL refernece and it was code 1-Primary Heated Oxygen Sensor...High/Low Signal??? i know this isnt the way to get the code..or is it?