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Subject: "connecting rear o2 to the front o2 output"

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rs-pssst	Jan-28-05 08:55 AM
Member since Nov 13th 2004 158 posts,

#85330, "connecting rear o2 to the front o2 output"

I am trying to get buy my shot rear o2 sensor and not have the CEL codes for the rear oxygen sensor. I had an idea to connect the output of the front o2 sensor to the rear o2 sensor input on the ECU. Would this fool the ECU into thinking the rear is actually there and functioning properly? Or by doing that, is it going to make it think that the cat isn't there and spit out a code anyways?

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Replies to this topic

RE: connecting rear o2 to the front o2 output, cougar694u, Jan-28-05 09:05 AM, #1

RE: connecting rear o2 to the front o2 output, rs-pssst, Jan-28-05 09:13 AM, #2

RE: connecting rear o2 to the front o2 output, 97whitESi, Jan-28-05 10:50 AM, #3

RE: connecting rear o2 to the front o2 output, rs-pssst, Jan-28-05 02:15 PM, #4

RE: connecting rear o2 to the front o2 output, 96eclipse2nr, Jan-28-05 05:03 PM, #5

RE: connecting rear o2 to the front o2 output, rs-pssst, Jan-29-05 05:16 PM, #6

RE: connecting rear o2 to the front o2 output, Blizare, Jan-29-05 09:10 PM, #7

RE: connecting rear o2 to the front o2 output, Administrator

Administrator

CODE4, Jan-30-05 06:50 AM, #8

RE: connecting rear o2 to the front o2 output, 96eclipse2nr, Jan-30-05 12:33 PM, #9

RE: connecting rear o2 to the front o2 output, 97whitESi, Jan-30-05 06:36 AM, #10

RE: connecting rear o2 to the front o2 output, Team

Team

ner947, Jan-30-05 09:42 AM, #11

RE: connecting rear o2 to the front o2 output, Global Ruler Of All Things

Global Ruler Of All Things

DarkOne, Jan-30-05 10:01 AM, #12

RE: connecting rear o2 to the front o2 output, rs-pssst, Jan-30-05 06:42 PM, #13

RE: connecting rear o2 to the front o2 output, WickedESi, Jan-30-05 07:01 PM, #14

RE: connecting rear o2 to the front o2 output, mcgyvr, Jan-31-05 02:16 AM, #15

RE: connecting rear o2 to the front o2 output, 97grnRS, Feb-02-05 10:15 AM, #16

RE: connecting rear o2 to the front o2 output, Global Ruler Of All Things

Global Ruler Of All Things

DarkOne, Feb-02-05 10:54 AM, #17

RE: connecting rear o2 to the front o2 output, 97grnRS, Feb-02-05 01:13 PM, #18

RE: connecting rear o2 to the front o2 output, WickedESi, Jun-28-05 07:52 AM, #19

RE: connecting rear o2 to the front o2 output, Keith2172, Feb-02-05 11:51 AM, #20

RE: connecting rear o2 to the front o2 output, MCubed45, Feb-02-05 01:54 PM, #21

RE: connecting rear o2 to the front o2 output, Keith2172, Feb-03-05 04:28 AM, #22

RE: connecting rear o2 to the front o2 output, Team

Team

ner947, Feb-02-05 05:55 PM, #23

RE: connecting rear o2 to the front o2 output, Administrator

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CODE4, Feb-03-05 03:08 AM, #24

RE: connecting rear o2 to the front o2 output, mcgyvr, Jun-29-05 01:28 AM, #25

RE: connecting rear o2 to the front o2 output, 96eclipse2nr, Jun-29-05 02:07 PM, #26

RE: connecting rear o2 to the front o2 output, mcgyvr, Jun-29-05 04:06 PM, #27

RE: connecting rear o2 to the front o2 output, WickedESi, Jun-29-05 04:19 PM, #28

RE: connecting rear o2 to the front o2 output, WickedESi, Jul-02-05 10:42 PM, #29

RE: connecting rear o2 to the front o2 output, rs-pssst, Jul-03-05 01:58 AM, #30

RE: connecting rear o2 to the front o2 output, buenrostrox, Sep-06-06 08:37 AM, #31

RE: connecting rear o2 to the front o2 output, valdeelrico, Sep-16-11 12:46 PM, #32

RE: connecting rear o2 to the front o2 output, Administrator

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CODE4, Sep-16-11 02:12 PM, #33

cougar694u	Jan-28-05 09:05 AM
Donating 2GNT member 3381 posts,

#85331, "RE: connecting rear o2 to the front o2 output"
In response to Reply # 0

Originally posted by rs-pssst
Or by doing that, is it going to make it think that the cat isn't there and spit out a code anyways?

Exactly.

maybe resistor mod the wires for the second o2 while it's hooked up to the front o2 maybe emoji

It may cause the car to think it's lean if you do that, but I really don't know.

~Luke
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2007 GSXR 750
1999 OZ - SOLD - 15.26 NA - 14.71 on 75 shot

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rs-pssst	Jan-28-05 09:13 AM
Member since Nov 13th 2004 158 posts,

#85332, "RE: connecting rear o2 to the front o2 output"
In response to Reply # 1

yea, i think i'm gonna just try to see what happens. my car is running way to rich (10.0afr) and i think its cause of the rear o2 being shot. does anyone have any voltages logged for the rear o2 sensor?

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97whitESi	Jan-28-05 10:50 AM
Member since Mar 17th 2004 1334 posts,

#85334, "RE: connecting rear o2 to the front o2 output"
In response to Reply # 2

Originally posted by rs-pssst
yea, i think i'm gonna just try to see what happens. my car is running way to rich (10.0afr) and i think its cause of the rear o2 being shot. does anyone have any voltages logged for the rear o2 sensor?

the rear o2 doesnt have any authority on pulsewidth ?

2005 Legacy GT Ltd, Garnet Red Pearl
speak softly and spool a big turbo

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rs-pssst	Jan-28-05 02:15 PM
Member since Nov 13th 2004 158 posts,

#85354, "RE: connecting rear o2 to the front o2 output"
In response to Reply # 3

I thought it was discussed that if there is a check engine code displayed for the rear o2 sensor, that the computer will go into a "safe mode" and run rich or mess with timing?

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96eclipse2nr	Jan-28-05 05:03 PM
Donating 2GNT member 3605 posts,

#85363, "RE: connecting rear o2 to the front o2 output"
In response to Reply # 4

it was discussed that a nonexistant/faulty rear o2 sensor will pull timing, but not have any bearing on your a/f ratio nor will it cause the computer to go into "limp" mode. if you dont want the cel, do the resistor mod. and if your running a turbo like your name suggests, how about tuning with your fuel system...thats why your running rich

-----------------------------------------
2011 Nissan Xterra Pro-4x

2007 Kawasaki Ninja 650R

1996 Mitsubishi Eclipse RS-NX 75 shot, AEM CAI, P&P t/b and intake mani-SOLD

1964 Buick Electra 225-all original, all power options, 325hp, 445ft/lbs tq

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rs-pssst	Jan-29-05 05:16 PM
Member since Nov 13th 2004 158 posts,

#85388, "RE: connecting rear o2 to the front o2 output"
In response to Reply # 5

causing the computer to pull timing is a problem -is it solved with the resistor mod? I am runnng turbo (18 psi daily driver) which is why i am worried about timing.

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Blizare	Jan-29-05 09:10 PM
Donating 2GNT member 7595 posts,

#85392, "RE: connecting rear o2 to the front o2 output"
In response to Reply # 6

Originally posted by rs-pssst
(18 psi daily driver) which is why i am worried about timing.

cough* megasquirt cough*

I eat emo kids for breakfast

1995 Eagle Talon (SOLD)
72' SuperBeetle
72' Standard Beetle
56' Deluxe Beetle

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CODE4	Jan-30-05 06:50 AM
Member since Nov 23rd 2003 2552 posts,

#85400, "RE: connecting rear o2 to the front o2 output"
In response to Reply # 5

Originally posted by 96eclipse2nr
it was discussed that a nonexistant/faulty rear o2 sensor will pull timing, but not have any bearing on your a/f ratio nor will it cause the computer to go into "limp" mode.

Where was this discussed? I am unable to find any data backing that. In my professional auto service experience, OBDII systems use the rear O2 input only for checking the catalyst.

Doing the resistor mod on the rear oxygen sensor, if done correctly, is not installing a resistor by itself. There is a capacitor in there as well. If watching the signal from an oxygen sensor there is a fluctuating signal as the computer continually pulls and adds fuel. The computer compares the fluctuating signal of the rear to the front. If they are identical then it knows the catalyst is not doing its job. With the catalyst performing as it should, the rear signal lags behind the front as the chemical reactions take place in the honeycomb inside the catalyst. Replacing the rear sensor with a resistor and capacitor creates a false fluctuating signal as the capacitor charges and discharges.

http://zero-signal.org/o2/O2bypass.html.htm

---

2012 2500HD LML

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96eclipse2nr	Jan-30-05 12:33 PM
Donating 2GNT member 3605 posts,

#85405, "RE: connecting rear o2 to the front o2 output"
In response to Reply # 8

Originally posted by CODE4

Originally posted by 96eclipse2nr it was discussed that a nonexistant/faulty rear o2 sensor will pull timing, but not have any bearing on your a/f ratio nor will it cause the computer to go into "limp" mode.

Where was this discussed? I am unable to find any data backing that. In my professional auto service experience, OBDII systems use the rear O2 input only for checking the catalyst. Doing the resistor mod on the rear oxygen sensor, if done correctly, is not installing a resistor by itself. There is a capacitor in there as well. If watching the signal from an oxygen sensor there is a fluctuating signal as the computer continually pulls and adds fuel. The computer compares the fluctuating signal of the rear to the front. If they are identical then it knows the catalyst is not doing its job. With the catalyst performing as it should, the rear signal lags behind the front as the chemical reactions take place in the honeycomb inside the catalyst. Replacing the rear sensor with a resistor and capacitor creates a false fluctuating signal as the capacitor charges and discharges. http://zero-signal.org/o2/O2bypass.html.htm

http://forums.2gnt.com/dcboard.php?az=show_topic&forum=8&topic_id=81632&mesg_id=81632&listing_type=search

Originally posted by Collentethe rear 02 will do something when it sences the cat has taken a shit. It will pull timing, This has been dyno proven by hrc. But it wont really hurt fuel performance. That is all taken care of by the upstream 02.

-----------------------------------------
2011 Nissan Xterra Pro-4x

2007 Kawasaki Ninja 650R

1996 Mitsubishi Eclipse RS-NX 75 shot, AEM CAI, P&P t/b and intake mani-SOLD

1964 Buick Electra 225-all original, all power options, 325hp, 445ft/lbs tq

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97whitESi	Jan-30-05 06:36 AM
Member since Mar 17th 2004 1334 posts,

#85399, "RE: connecting rear o2 to the front o2 output"
In response to Reply # 0

Originally posted by rs-pssst
I am trying to get buy my shot rear o2 sensor and not have the CEL codes for the rear oxygen sensor. I had an idea to connect the output of the front o2 sensor to the rear o2 sensor input on the ECU. Would this fool the ECU into thinking the rear is actually there and functioning properly? Or by doing that, is it going to make it think that the cat isn't there and spit out a code anyways?

no, that would tell it exactly what its throwing a cel for,

in our cars, the downstream o2 trips a cel if the rear o2 is >.7x the front (MTX) or >.9x the front (ATX)

2005 Legacy GT Ltd, Garnet Red Pearl
speak softly and spool a big turbo

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ner947	Jan-30-05 09:42 AM
Donating 2GNT member 3168 posts,

#85401, "RE: connecting rear o2 to the front o2 output"
In response to Reply # 0

I had an interesting discussion at the Shootout with Bill and a bunch of other people about just this. The rear oxygen sensor DOES have an effect on peformance. It's there mainly to test the efficiency of the catalytic converter, but we all came to the conclusion that the ECU probably treats an oxygen sensor failure as a global error, regardless of which oxygen sensor is stuck putting out one voltage level.

The rear sensor's voltage should always be lower than the front one. This means the catalytic converter is working. The ECU will also check to make sure that both sensors are changing value, and that they are not stuck at one voltage. Therefore, if the rear oxygen sensor is stuck at one value (you have an exhaust cutout before the sensor or it's broken or disconnected) the ECU will treat it as if the front oxygen sensor has failed - it will fall back an open loop fuel map and will retard the timing.

I was a little drunk when we had that conversation at the shootout. Anyone care to elaborate?

2016 WRX STi Limited (current)
2001 A4 1.8tqms (donated)
1991 GVR4 #1933 (sold)
old.dsmregistry.com/detail.php?carid=218 (dismantled)

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DarkOne	Jan-30-05 10:01 AM
Donating 2GNT member 14955 posts,

#85402, "RE: connecting rear o2 to the front o2 output"
In response to Reply # 11

Originally posted by ner947
I was a little drunk when we had that conversation at the shootout. Anyone care to elaborate?

I was too, but that's the gist of it. An O2 failure is an O2 failure, regardless of front or rear, and both will cause the same problems.. Open loop, pulled timing, loss of power and performance.

Y'all might get a kick out of this, but i figured out why my car never threw a no-cat CEL... i pulled the rear O2 out, and it was a solid cone of carbon... Nice.

______________________________
If a sentence found online has 35% misspellings or greater and includes at least two racially charged expletives, chances are it is a YouTube comment.

'95 Eclipse TurboGS (garage deco)
'95 TSi AWD (restoring a survivor)
'97 Talon ESi-T (poor impulse control)
'99 Eclipse RS-T (daily beater)
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rs-pssst	Jan-30-05 06:42 PM
Member since Nov 13th 2004 158 posts,

#85416, "RE: connecting rear o2 to the front o2 output"
In response to Reply # 12

So if the rear o2 is supposed to be reading lower voltages than the front and fluctuating... then couldn't the ouput of the front o2 sensor be hooked into the input of the rear o2 but with a resistor in between to lower the voltage?

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WickedESi	Jan-30-05 07:01 PM
Donating 2GNT member 3090 posts,

#85417, "RE: connecting rear o2 to the front o2 output"
In response to Reply # 12
Jan-30-05 07:03 PM by WickedESi

Originally posted by DarkOne

Originally posted by ner947 I was a little drunk when we had that conversation at the shootout. Anyone care to elaborate?

I was too, but that's the gist of it. An O2 failure is an O2 failure, regardless of front or rear, and both will cause the same problems.. Open loop, pulled timing, loss of power and performance. Y'all might get a kick out of this, but i figured out why my car never threw a no-cat CEL... i pulled the rear O2 out, and it was a solid cone of carbon... Nice.

If you're not getting a CEL will it still pull timing?

Joel Baldridge, ASE Certified Master Technician, Audi Certified Expert Technician

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mcgyvr	Jan-31-05 02:16 AM
Old School 2GNTer 3121 posts,

#85420, "RE: connecting rear o2 to the front o2 output"
In response to Reply # 14

casper electronics makes an o2 simulator, $40 bucks or so and problem solved.
The resistor trick usually works on most vehicals though, but the capser device works without a problem

1998 dodge avenger 4 cyl AT
Mods are:
Not enough

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97grnRS	Feb-02-05 10:15 AM
Member since Jul 24th 2004 564 posts,

#85513, "RE: connecting rear o2 to the front o2 output"
In response to Reply # 14

with that o2 sensor link that was given it talks about using a 12 ohm resistor in between the heater wire and another wire. is this needed? couldnt the heater wire just be cut and taped off?? the only necessary thing should be the capacitor and the resistor between the power and signal wire right? that should fool the ecu? the grnd and heater can just be left cut off right?

91 civic hatch, homemade turbo+ LS motor = 12 sec street car.

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DarkOne	Feb-02-05 10:54 AM
Donating 2GNT member 14955 posts,

#85514, "RE: connecting rear o2 to the front o2 output"
In response to Reply # 16

NO. The ECU checks the heater circuit too.

______________________________
If a sentence found online has 35% misspellings or greater and includes at least two racially charged expletives, chances are it is a YouTube comment.

'95 Eclipse TurboGS (garage deco)
'95 TSi AWD (restoring a survivor)
'97 Talon ESi-T (poor impulse control)
'99 Eclipse RS-T (daily beater)
'13 Evo X (mostly stock)
'17 Sienna (Middle Aged Dad Mobile)

Factory Service Manuals: http://nawdu.de/files/

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97grnRS	Feb-02-05 01:13 PM
Member since Jul 24th 2004 564 posts,

#85516, "RE: connecting rear o2 to the front o2 output"
In response to Reply # 17

ok well is that link color specific to our cars or is it general ? cause my o2 wires are not that color. i got a black . two white and a grey

91 civic hatch, homemade turbo+ LS motor = 12 sec street car.

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WickedESi	Jun-28-05 07:52 AM
Donating 2GNT member 3090 posts,

#91005, "RE: connecting rear o2 to the front o2 output"
In response to Reply # 12

Originally posted by DarkOne

Originally posted by ner947 I was a little drunk when we had that conversation at the shootout. Anyone care to elaborate?

I was too, but that's the gist of it. An O2 failure is an O2 failure, regardless of front or rear, and both will cause the same problems.. Open loop, pulled timing, loss of power and performance. Y'all might get a kick out of this, but i figured out why my car never threw a no-cat CEL... i pulled the rear O2 out, and it was a solid cone of carbon... Nice.

I have a rear o2 slow response code (the rear o2 sensor isn't hooked up at all), and it is not in open loop. The timing is not retarded at all either I don't think. So is this just a myth then? I'm about to go to radioshack to make a simulator just to get rid of the cell though. BTW, wouldn't it be a good thing for us turbo guys to retard the timing and stay in open loop because of the part throttle boosting problems?

Joel Baldridge, ASE Certified Master Technician, Audi Certified Expert Technician

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Keith2172	Feb-02-05 11:51 AM
Member since Jan 16th 2004 1281 posts,

#85515, "RE: connecting rear o2 to the front o2 output"
In response to Reply # 11

Originally posted by ner947
I had an interesting discussion at the Shootout with Bill and a bunch of other people about just this. The rear oxygen sensor DOES have an effect on peformance. It's there mainly to test the efficiency of the catalytic converter, but we all came to the conclusion that the ECU probably treats an oxygen sensor failure as a global error, regardless of which oxygen sensor is stuck putting out one voltage level. The rear sensor's voltage should always be lower than the front one. This means the catalytic converter is working. The ECU will also check to make sure that both sensors are changing value, and that they are not stuck at one voltage. Therefore, if the rear oxygen sensor is stuck at one value (you have an exhaust cutout before the sensor or it's broken or disconnected) the ECU will treat it as if the front oxygen sensor has failed - it will fall back an open loop fuel map and will retard the timing. I was a little drunk when we had that conversation at the shootout. Anyone care to elaborate?

so the solution to this is...

It appears to me that the resistor mod should still work so long as the resistor is sufficient. A resistor won't stop it from fluctuating will it? I was discussing it with one of my buddies and we were thinking the signal wire to a t-off, a 20% resistor to the harness and an 80% resistor to ground (grnd-80%-signal-20%-harness) it makes more sense on paper. Anyways, if you get what Im saying, tell me if Im right or wrong please.

Representing the Central Cali chapter of 2GNT!
(I think I'm the only member emoji )

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MCubed45	Feb-02-05 01:54 PM
Member since Sep 17th 2002 2706 posts,

#85519, "RE: connecting rear o2 to the front o2 output"
In response to Reply # 20
Feb-02-05 02:00 PM by MCubed45

doesn't the ecu read the voltage drop across the oxygen sensor? and the resistance of the sensor changes with the oxygen content? if so then i don't see how using just a resistor would possible give a fluctuating signal. the resistance and current are being held constant so why would the voltage drop change?

V=I*R

sorry if i'm way off on my understanding of how an 02 sensor works...

If the ECU needs to see a fluctuating signal then it makes a lot of sense to use the setup with the capacitor. Using just a resistor will not give you a changing voltage. I'm not sure if using just a resistor works on our cars or not, but if you're doing the mod, would it really be so hard to solder in a capacitor at the same time? emoji

-marc

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Keith2172	Feb-03-05 04:28 AM
Member since Jan 16th 2004 1281 posts,

#85531, "RE: connecting rear o2 to the front o2 output"
In response to Reply # 21
Feb-03-05 04:28 AM by Keith2172

Originally posted by MCubed45
... If the ECU needs to see a fluctuating signal then it makes a lot of sense to use the setup with the capacitor. Using just a resistor will not give you a changing voltage. I'm not sure if using just a resistor works on our cars or not, but if you're doing the mod, would it really be so hard to solder in a capacitor at the same time? emoji

My point is that a resistor won't change the fluctuation at all, it will still fluctuate. All the resistor does is drop the voltage a little. You want to duplicate what the Cat. does right? Well from an electrical standpoint, what does it do? It provides resistance, it lowers the amount of hydrocarbons (or whatever the O2 sensor see's) and provides more resistance. Am I way off here?

Representing the Central Cali chapter of 2GNT!
(I think I'm the only member emoji )

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ner947	Feb-02-05 05:55 PM
Donating 2GNT member 3168 posts,

#85523, "RE: connecting rear o2 to the front o2 output"
In response to Reply # 20

Sure. Try a simple voltage divider. Just be careful of what size resistors you pick. Too low and it will pull too much current from the front oxygen sensor. Too high and there won't be enough there to drive the input of the ECU.

I'd start off with...

Front O2 EGO -> 5k? resistor -> rear sensor wire that goes to the ECU -> 5k? resistor to ground

Give that a shot. It will flow about .1 milliamps, tops, which is nothing. I mean, you're not gonna break anything. If you ground the oxygen sensor, the worst thing that can happen is that you will need a new one. If you short an ECU input to something, I doubt that would do much of anything either. Those inputs should be high impedence.

2016 WRX STi Limited (current)
2001 A4 1.8tqms (donated)
1991 GVR4 #1933 (sold)
old.dsmregistry.com/detail.php?carid=218 (dismantled)

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CODE4	Feb-03-05 03:08 AM
Member since Nov 23rd 2003 2552 posts,

#85526, "RE: connecting rear o2 to the front o2 output"
In response to Reply # 23

I got parts coming in today for my O2 sensor eliminator. Using high watt wirewound resistors for the heating element (about 30 watt capability to be safe) and a resistor and cap. for signal circuit. I am putting it in an enclosure as well for heatsinking. I will take a few pics and let you guys know how it works.

---

2012 2500HD LML

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mcgyvr	Jun-29-05 01:28 AM
Old School 2GNTer 3121 posts,

#91017, "RE: connecting rear o2 to the front o2 output"
In response to Reply # 24

just buy a new rear o2 sensor and stop fucking around.
no matter what you do with resistors some cars will still have the code come right back.

1998 dodge avenger 4 cyl AT
Mods are:
Not enough

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96eclipse2nr	Jun-29-05 02:07 PM
Donating 2GNT member 3605 posts,

#91027, "RE: connecting rear o2 to the front o2 output"
In response to Reply # 25

Originally posted by mcgyvr
just buy a new rear o2 sensor and stop fucking around. no matter what you do with resistors some cars will still have the code come right back.

yeah, but to those with test pipes and gutted cats, you cant just solve the CEL by replacing the sensor...if you wanna continue to run that setup, you gotta eleminate it. true, if you have a fully functioning catalyist system...and ur light is on...yeah, stop messin around and buy another one. but thats not a solution for people who actually CAUSE this problem by bypassing emissions equip.

-----------------------------------------
2011 Nissan Xterra Pro-4x

2007 Kawasaki Ninja 650R

1996 Mitsubishi Eclipse RS-NX 75 shot, AEM CAI, P&P t/b and intake mani-SOLD

1964 Buick Electra 225-all original, all power options, 325hp, 445ft/lbs tq

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mcgyvr	Jun-29-05 04:06 PM
Old School 2GNTer 3121 posts,

#91028, "RE: connecting rear o2 to the front o2 output"
In response to Reply # 26

yeah but your killing my air/trees emoji
seriously for the 1hp and the raspy sound your gaining its not worth it. IMO
keep emissions intact, just up the boost emoji

Seriously the casper o2 simulator is the way to go, solves the problem right away.

1998 dodge avenger 4 cyl AT
Mods are:
Not enough

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WickedESi	Jun-29-05 04:19 PM
Donating 2GNT member 3090 posts,

#91029, "RE: connecting rear o2 to the front o2 output"
In response to Reply # 26

Originally posted by 96eclipse2nr

Originally posted by mcgyvr just buy a new rear o2 sensor and stop fucking around. no matter what you do with resistors some cars will still have the code come right back.

yeah, but to those with test pipes and gutted cats, you cant just solve the CEL by replacing the sensor...if you wanna continue to run that setup, you gotta eleminate it. true, if you have a fully functioning catalyist system...and ur light is on...yeah, stop messin around and buy another one. but thats not a solution for people who actually CAUSE this problem by bypassing emissions equip.

I don't have a rear o2 sensor laying around, nor the harness to plug one in into.

I made one of these eliminators yesterday, http://www.vfaq.com/mods/O2bypass.html, exactly as shown other than running a 10 ohm 10 watt, and 2x 1 ohm 10 watt resistors in series to get the 12 ohms capable of handling 12 watts (since they don't make any 12 ohm 12 watt resistors that I'm aware of). I'll splice it in in the morning.

Joel Baldridge, ASE Certified Master Technician, Audi Certified Expert Technician

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WickedESi	Jul-02-05 10:42 PM
Donating 2GNT member 3090 posts,

#91113, "RE: connecting rear o2 to the front o2 output"
In response to Reply # 28
Jul-02-05 10:43 PM by WickedESi

Well the do it yourself eliminator got rid of my error codes, and I didn't even eliminate the heater signal (I'm a '95 btw, so it may vary). I made the heater eliminator as stated above ^^^ but my resistors got so hot it melted the plastic bag I threw it in (didn't have large enough heat shrink for it yet). So if you do the resistor and capacitor and still get an error code for the heater then I would try 3x 36 ohm 10 watt resistors in parallel. I did the 10 ohm 10 watt and 2x 1 ohm 10 watt in series and the 10 ohm resistor was at max load (10 watts of heat absorbed by it) and would burn you if you touched it.

So in other words... I spent < $2 to get rid of the rear o2 sensor permanently. Happy ECU, no CELs...

I can't believe how much people are able to sell these eliminators for.

Joel Baldridge, ASE Certified Master Technician, Audi Certified Expert Technician

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rs-pssst	Jul-03-05 01:58 AM
Member since Nov 13th 2004 158 posts,

#91114, "RE: connecting rear o2 to the front o2 output"
In response to Reply # 29

It worked, if your rear O2 sensor is shot, then take the front O2 sensor and pipe it into the rear input on the ecu. Put a resistor inline of that connection to the ecu using the resistance outlined in the resistor mod.

I passed emissions doing it that way.

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buenrostrox	Sep-06-06 08:37 AM
Member since Apr 14th 2005 11 posts,

#100848, "RE: connecting rear o2 to the front o2 output"
In response to Reply # 30

FUCK!!!

I went to Casper's website to get the o2 Simulator and look!

https://www.casperselectronics.com/Merchant2/merchant.mvc

Read the top of the page. :'(

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valdeelrico	Sep-16-11 12:46 PM
Member since Mar 06th 2009 41 posts,

#135109, "RE: connecting rear o2 to the front o2 output"
In response to Reply # 11

Originally posted by ner947
I had an interesting discussion at the Shootout with Bill and a bunch of other people about just this. The rear oxygen sensor DOES have an effect on peformance. It's there mainly to test the efficiency of the catalytic converter, but we all came to the conclusion that the ECU probably treats an oxygen sensor failure as a global error, regardless of which oxygen sensor is stuck putting out one voltage level. The rear sensor's voltage should always be lower than the front one. This means the catalytic converter is working. The ECU will also check to make sure that both sensors are changing value, and that they are not stuck at one voltage. Therefore, if the rear oxygen sensor is stuck at one value (you have an exhaust cutout before the sensor or it's broken or disconnected) the ECU will treat it as if the front oxygen sensor has failed - it will fall back an open loop fuel map and will retard the timing. I was a little drunk when we had that conversation at the shootout. Anyone care to elaborate?

I have a bank one running rich code and my flex pipe on the exhaust is cracked letting fresh air in the exhaust before the catalyst. Guess I'll fix that first before I do anything else.

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CODE4	Sep-16-11 02:12 PM
Member since Nov 23rd 2003 2552 posts,

#135110, "RE: connecting rear o2 to the front o2 output"
In response to Reply # 32

Alright, read the damn post date, holmes.

---

2012 2500HD LML

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