passed obdii today with 45ohms (4 25watt resistors in series) between one heater wire and the other I started out near the tech manual lower limits, but the resistor got too hot so I put everything I had in series and built a little metal box to put them in and voila! no heat and no CEL

I still have a cat code pending, but pending means it doesn't affect your test(apparently, I wasn't sure this morning when I left the house).

 

1.

The first part is to eliminate the actual sensor part of the O2 sensor.
http://www.vfaq.com/proj-pics/o2bypass.gif


This is how our circuit will more or less be, note that we won't have the O2 sensor at all anymore. Here's our schematic:
http://www.vfaq.com/proj-pics/O2bypa1.gif

2. Take the 1Mohm (that's 1,000,000 ohms) and the 1µF (micro-farad) capacitor and solder the two together in parallel.
3. Remove the front seat from your car and detach the two O2 sensor harnesses from each other. You want to work on the harness side that is attached to the O2 sensor (it's easiest). Cut all 4 wires leaving about 2.5-3" of wire. You should now be able to remove the harness piece from the car.
4. Strip ¼-½" of insulation off of the blue and white wires. Solder your two components onto the blue and white wires.
5. Tape/heatshrink everything up and make sure that nothing is shorting against anything else.
6. Now we'll eliminate the heater element of the circuit. You'll need a resistor of ~12 Ohms. This heater element flows around 1 Amp of current so you'll need resistors that can dissipate at least 12 Watts of current. Don't scrimp here as under-rated resistors could set your car on fire.
7. Strip the two black wires, solder the resistor in between the two wires. Tape/heatshrink everything well.
8. Plug the harness back into the other ECU side of the harness and put your seat back in.
http://www.vfaq.com/mods/O2bypass.html

This was done on an eclipse, perhaps it would work? it looks very simple and from what ive seen we have those four wires haha this seems less dangerous

 

Ok, this sound interesting. I'm giong to try it today (if I find the parts in Radio Shack) i have only 2 questions.

1. Where exactly is the O2 plug (under what seat?)
2. I see that the 12 Ohms resistor need to dissipate 12 watts of current, what about the 1Momh one??? does it have to be specific or can it be anyone??

 

12 ohms will probably generate a lot of heat. the wattage rating merely tells you how much power the resistor can handle. the heat is dependent on the current, which is dependent on the resistance. more resistance is less heat.

I started with ~6ohms and immediately changed to the 20ohm, both were too hot. 45 made almost no heat, or none I can feel outside the box I made anyway. the 6 (maybe the 20, I don't remember trying after it started getting too hot to touch) was capable of melting electrical tape after a short time with the engine on.

I used 25 watts to be sure the resistors would not blow. same reason I didn't take hackish's suggestion on the 1kohm: I only had one rated to 1/2 watt.

 

this is only for the rear sensor, which is under the passenger seat and can be accessed just fine from under the car. the front one you have to get at from above, the plug won't pull through the hole (or it wouldn't on my car ) and it is behind the console kick panel on the passenger side.

the rating for the o2 sim "shouldn't" matter, there is very little current in a signal line. the high current in the heater line is necessary to create the heat.

 

I know is for the rear. If this work i will replace the rear one with the wideband I am about to buy. So, Dan you recomend I use a 45 Ohm resistor instead of the 12Ohm one?? BTW I havent forgotten you, I'll PM you later tonight.

 

I used four resistors in series to add up to 45ohms and "no heat" so I could leave the box on the floorboard and not worry about the carpet. it must be at least what is in the tech manual, but my understanding of this circuit is that the ceiling is infinite, as eventually the heater is supposed to go off (when it's not needed) I bought resistors starting at the minimum value and once it started getting so hot I decided to throw them all together. I checked just now to be sure, but the only code I have is the cat code.

the rear sensor test values for the heater resistance are 11 to 18 ohms at 68*F. 12ohms barely gets you over the test limit, which I assume is also the ECU error limit. better have a resistor with ~5% tolerance

I'd recommend buying something in the 40-60 range if you want to only one, but they are so cheap you should really buy a selection (say 15, 20, and 25 ohms) so you have options. it's one thing to know a solution works long term, but my box has only been on since Sunday so I am not certain it won't come back later on. the ECU tests different conditions over different periods of time for the CEL, so if your CEL goes off initially but comes back after a month you can add a little more resistance to the circuit. I would only assume it would test for the sensor getting hot enough to give accurate readings, and if the sensor is always "cold" (heater always "on") the ECU may eventually not like it.

np, not like I'm in a rush to pull the interior ttyl

 

btw, your high flow cat could screw up the readings on the wideband somewhat. read up a bit on how the cat changes the chemical composition of the gases, and what that does to the wideband readings.

 

I just got back and got a 50 Ohm 10 watt/10% tolerance resistor. I wont be cutting the factory O2 Plug because i have a ton of cable and different connectors. When i'm done ill post back, wish me luck.

 

:crossesfinger: @ 10watt :X

 

Ok, no time for it today. I spent all my evening installing a custom made ground kit and changing my dash lights. This project will have to wait till next week. Sorry guys.

About the 10 watt resistor it was the best I could find in Radio Shack, I was thinkind about using two of those in line but dont know if it will work like that, what do you think.

 

it doesn't increase the power rating, only the resistance.

 

i have a p0031 code which is sensor one heater circuit low, what exactly does that mean?

 

the heater on your upstream O2 sensor is probably on its way out?

I forget which code I have... but i know for sure my O2 sensor is shot... (the heater core only)