Okay so I have a 95 extended cab 22RE 4WD pickup and I live in Texas. My question is, is it possible to bypass that secondary (California emissions) O2 sensor or do I have to replace it since I replaced the exhaust and don't have an O2 sensor in it now, of course causing the check engine light to come on. Can I just splice some of the wires coming from the underside of the truck to the plug?

 

More will chime in here soon. But as far as I know, you should replace it. The ECU uses 2 sensors. One in front of the cat and one behind, that way it knows whats going on before and after the cat. I don't think bypassing it would be a good idea. The more information the ECU has, the better the decisions it can make. Thats the idea anyways, who knows if its true uh?

 

The second O2 sensor checks to see if the CAT is working. The second O2 sensor is supposed to show a very damped swing, because the CAT has used up the oxygen doing it's job. If the O2 readings of the two O2 sensors go up and down together, that means the CAT isn't doing anything, and you get a nice polite code.

If you were a whole smarter than I am, you might be able to figure out some circuit that could fool your ECU into thinking the second O2 sensor is really there (of course, that circuit would cost more than a real O2 sensor). So unless you get a different ECU, you're probably going to need that sensor.

 

Depends on Texas!!

What do you have as far as emission inspections??

Here in Pa if you have the California Emissions package it all has to be there .

The two cats as well as all the sensors.

If the CEL is on of course that needs to be addressed before your good to go.

like was said you can get something from Under Dog Racing to give the ECU the information the ecu needs to see.

but a lot cheaper to just install the proper sensor.

 

Back when I had a mustang, there was a company making o2 sensor "sims" that you used instead that would tell the ECM everything was in range.

Not legal, but they do exist

 

You can look here, doesnt look like they are taking orders anymore, from what I hear all of the simulators have been taken off the market.

http://www.o2simulator.com/?gclid=CK...FakZQgodTUQrVw

 

I just bought a 1990 4runner that has a random mis fire while idling but fine when driving. The cat is hollow and the ECU and TPS have been replaced multiple times with no results. Does anyone know what it might be? I have heard that it could be a gremlin in the wiring but is that true?

 

Dum

 

Your spinning your wheels trying to bypass it, I know their a couple$$. But replacing it is the way to go.

 

Search for answers and then start a new thread. Don't hijack some else's.

 

There are 2 ways to bypass the downstream O2 that I know of... 1st, obviously is the o2 eliminator kit, it costs more than the replacement o2, so whats the point?

2nd way , is a lil cheaper, got to a boneyard near you, and find a rig just like urs, but 94 or 93, without the downstream o2, and grab the ecu )$20-50) if u have an auto, the ecu needs to be from an auto as well, if urs is 5spd, then either will work. Bam... no more cel! My 94 in my sig, has the downstream o2, and is a 5spd, cat clogged up, so I gutted it, and had to do something about the cel, I happened to have an extra ecu for my 93 (also in my sig) which is an auto and has no downstream o2, popped that puppy in, and havent seen the cel since :-)

I would, as always recommend fixing it correctly, but if your short on cash or need a new cat as well, this can get ya by for a lil while