O2 Sensor voltage

[shawnme]

bros,
as far as i understand, O2 sensors should produce a voltage between 0-1V
so i went ahead with the diy project for the AF ratio ...and somehow..
when i tried to measure the voltage with the multimeter, regardless of the measurement point directly from the o2 sensor in the engine bay or the o2 sensor line from the ecu, it still gives me a reading of 2.8X volts and when i tried to rev a few times, it does show movement up to 3.1X volts.
so i thought maybe the sensor is not warmed up yet...so i waited for 20 minutes in idle mode...yet i still get the same reading..
so i'm wondering...what's the cause of this??...is this normal for my mivec gen 1 ???
i took measurements from 2 points just in case i got the wrong wire from ecu...and since i also measured directly from the o2 sensor itself, i dont think i got the wrong wire after all...
can someone enlighten....thanks ahead.
shawn

 

[ecupro]

I am not sure, but can give some knowledge.
You are right, normal o2 sensor will produce voltage from 0 to 1.0v or 1000mV.
This is narrow band sensor.
For A/F 14.4, voltage will be 680mV or 0.68V
On Rich Side, voltage will be from 780mv or 0.78v
Arrr....one thing, do not use analog meter, this will loading the sensor output.
So, please use digital meter.
In your case, i thing it is a wide band sensor.It will produce from 0 to 5.0V
For A/F 14.4, voltage will be 2.5V. It is ok.
On Rich Side, voltage will be from 2.2V to ZERO.
If the sensor only have one or two wire, this kind of sensor did not built in HEATER element, do it will take as least 3 minutes to head it up( Chemical reaction ).
If the sensor have 3 to 4 wire, Heater element is build in.So, only take less then a minute, you will get reading.
By the way, LED A/F meter or Digital meter you are making ?

 

[shawnme]

I am not sure, but can give some knowledge.
You are right, normal o2 sensor will produce voltage from 0 to 1.0v or 1000mV.
This is narrow band sensor.
For A/F 14.4, voltage will be 680mV or 0.68V
On Rich Side, voltage will be from 780mv or 0.78v
Arrr....one thing, do not use analog meter, this will loading the sensor output.
So, please use digital meter.
In your case, i thing it is a wide band sensor.It will produce from 0 to 5.0V
For A/F 14.4, voltage will be 2.5V. It is ok.
On Rich Side, voltage will be from 2.2V to ZERO.
If the sensor only have one or two wire, this kind of sensor did not built in HEATER element, do it will take as least 3 minutes to head it up( Chemical reaction ).
If the sensor have 3 to 4 wire, Heater element is build in.So, only take less then a minute, you will get reading.
By the way, LED A/F meter or Digital meter you are making ?

i used digital meter for my readings...and it's a wide band??!!!!...then how am i gonna get my AFr
coz i've never changed anything...it's still the same mivec halfcut i got...only that it's in my car now...

and indeed, it has only 2 wires....i measured each of them....one of them is ignition 12V+ and the other is the 2.8+ volts wire..

i'm making the LED AF meter thingy...just to know for kicks my AF ratio...haha...

shawn

 

[ecupro]

Hem.....
What i know is two wire sensor with one white and one blue.
I think the blue for ground and white for signal.
It is narrow band o2 sensor.
Long time, my engine come with one wire o2 sensor. Now, i change to Mitsubishi, two wires( blue and white, almost standard on all Mitsubishi, my engine is 4G61T )

 

[sekut_kring]

Little info

I got this from my collection....hope this will give your a little help.


In order to read the O2 sensor, most computers send out a certain voltage to the output terminal of the sensor. This is typically around 450 millivolts. Since we know that the sensor sends low voltage (under 300mv) when a lean condition is present and a high voltage (over 600mv) when a rich condition is present, the computer can count the number of times the sensor crosses the 450mv mark. Cross-counts are the number of times an O2 sensor crosses 450mv. A scanner can "look" at this for you.

Even though you can't see the number of cross-counts without a scanner, you can use a digital voltmeter to watch the open/closed loop system operate. Just connect your meter as attachment, while the O2 sensor is still connected, and start-up the car.

Caution: Do not ground the output wire of the sensor. This can damage the sensor and your readings will be erroneous.

When the car starts (cold), you should see approximately .450 Volt (450mv) on the O2 output wire. This reading often varies slightly. The system is now in open loop.

After a few minutes (less if the engine is warm or the O2 Sensor is heated), this reading should begin to fluctuate. You will see changing numbers ranging from near 0 volt to near 1 Volt. If these readings occur, everything is ok. The O2 sensor's output should vary relatively quickly. A lazy sensor, would show up here and the readings will vary slowly. If the readings don't start to vary (stay in open loop), you now are aware of it and can begin to look for the reason.

 

[ecupro]

By the way, why 12V on that wire?
Is it stock wire?

 

[shawnme]

bros,

i followed the advice of bro sekut_kring and finally i got it to work...

however, it's weird that my AF meter jumps up and down like disco lights...

is it due to the open/close loop of the ecu???

but i've seen my friend's car and it does not jump up and down like that...

at idle, he gets 1 led

during pick up..usually rich

and during cruising, 13.4-14.7 (around there - i forgot)

which i find it logical...

how come mine doesnt work this way??

shawn

 

[ecupro]

Bro, is it on the same car model ?
For Mitsubishi (my car when using stock ecu), during cruising for a while ( rpm around 2000 to 2500, town area ), the led will go from left to right, then, right to left. This is call close loop system. While crusing, the ecu will check on the o2 sensor. When on rich side, o2 will generate more votalge, in this case, you led display will go from left to right ( lean to rich ), the ecu will re-calculate the fuel( close loop system) and so the fuel will reduce, in this case, you led display will got from right to left ( rich to lean ), and the whole process will be repeat until you accelate your car.

 

[shawnme]

yes..i'm using stock ecu...everything is pretty much stock....

just that when i compare it to my friends 4G93 with evo ecu, it doesnt jump like that..it's pretty much stable and easy to read...

the difference in his car would be dyno with safc2 and a rechip done...

could it be the difference of the dyno?? coz it's pretth much jumping around most of the time...it's currently kind of pointless reaading anything out of the AF meter...as it makes no sense...hehe...

shawn

 

[ecupro]

Bro, try put one 0.1uf capacitor on the input circuit board. It may dumper a bit.
( one leg on input, one leg to the ground, parallel ok )
By the way, please goto the threads: Tunning with a EGT and have a look look.

 

[Cheong Mou Kei 4G9XT]

hmm...im using stock ECU but da reading oso stable wert

 

[shawnme]

i've read through the EGT topic...great info...however, i'll still leave the tuning to the dyno...coz i dont really trust my O2 sensor....

what i'm doing now is just for kicks...and a cheap way hoping that i could monitor my engine and fueling....not really hardcore into tuning and stuff...

its like some first point of reference for me if something is wrong with the engine...

i will try the 0.1 uf cap....

anyway, i'm still curious to how come everyone else's runs stable and mine still fluctuates in the waves...i wonder if it's because i skip one part of the project...i didnt use the 'voltage regulator' (LM340MP - 5.0) in the input ....

thanks ahead,
shawn..

 

[shawnme]

bro,

i somehow found a 0.33uf capacitor lying about so i plugged it in...somehow, i slowed down the motions a little...however, i still get fluctuating close loop signals...

i soldered the negative side to ground and the positive side to the O2 signal input...

does this mean that i have a get a 0.1uf capacitor to be exact to be able to stabilize the signal??

shawn

 

[ecupro]

bro, Not 7805 ( 5 v regulator ), Its a 7812 ( 12 v regulator ).
From your circuit, it seem there is no capacitor for the in comming battery voltage, try to but 470 uf, 25v.( In order to filter noise and dumpper a voltage a bit.
By the way, the input wire from o2 sensor must be shield ( if you tap from the stock ecu socket, i think it is ok )

I thing, ground or earthing the wire is very important on automobile.
Those who add in hi-fi system will know what i mean.

bro, have to try...try...try

 

[shawnme]

bro,

thanks for helping out this far...haha....i'm still trying....until i get it working...haha

well, i'll add another capacitor to the incoming 12V+ parellel to the ground..

dont really get what you mean by the voltage regulator though...anyway, i didnt use it....is it necessary???

by the way, i tap all my wires from the ecu...all ground, ignition and the o2 signal...

and i'm very curious...how do you know what capacitance to use??..how do you calculate???

thanks,
shawn...

 

[ecupro]

Well, when you engine running, the battery voltage will be > 12v.
We are talking on sensitive device.
Look at the electronic magazine.

 

[140dB]

shawn,

i made my own 02 sensor with the 3914 ic too.

my circuit is similar to yours, with the addition of a 39k resistor in series on the input. and the resistor between pins 6 and 7 is a pot so u can fine tune. on the supply side a 10 ohm resistor in series wif 12V, a 100uf cap for filtering and a 15v zener. i did not use any input cap.

my ecu is 4g13 mmc.

the leds do dance about for part throttle driving. floor it and see it go rich constantly.

this device helped me go fast on the higway without wasting too much fuel. i would floor it just before the point it kicks into open loop (usually 80-90% throtle). and if i accidently go open loop, i back off throtle till it goes back to closed loop (abt 70% throttle ).

hope this helps

 

[shawnme]

oh...thank you bros...

if you put it that way...then i guess it's working alright....just not as i've expected..hehe

when i floor it....or even just merely acc with >35% throttle , it already shows a stable rich condition...

so if i've not mistaken your words, close loop is the most efficient in fuel,,,am i right..

thanks,
shawn

 

[nukleus]

What i know is two wire sensor with one white and one blue.
I think the blue for ground and white for signal.
It is narrow band o2 sensor.

which one should i tap the sensor wire to my a/f ratio meter ?

the blue one or the white one? i already tap to the blue one but my meter only show lean to stoich only even with WOT never show rich...

i tap the wrong wire or my O2 sensor gone ?
can any one guied me...

 

[ecupro]

Ecupro,
I quote :
"What i know is two wire sensor with one white and one blue.
I think the blue for ground and white for signal.
It is narrow band o2 sensor."

Sorry, i made a mistake here...he...he..he
The Blue is a output signal and the White is ground.( Wira or EVO I~III , four wires, ie. with heater element )

nukleus,
You quote:
"which one should i tap the sensor wire to my a/f ratio meter ?

the blue one or the white one? i already tap to the blue one but my meter only show lean to stoich only even with WOT never show rich.."

Bro, from here, i think your engine is Mitsubishi.
Are you using the existing O2 and stock ecu ?
If yes, just follow the below diagram: (Pin 22.6, wire facing to you without disconnect ecu)

1 2 3 4 5 6 7 8 9 10 11
12 13 14 15.............22

ie. first row, column no.6

If Not, make sure you connect the heater element.

For more ref, please check on thread "Local ECU" on page 5 to 7

Good Luck.




i tap the wrong wire or my O2 sensor gone ?