9 replies to this topic

[FTodaro]

I am in the process of wiring up the rear O2 sensor in my 2000 build. I am not sure if it makes a difference, but its a California emissions car. there was no rear sensor, near the driver seat(it was under the hood) like on the federal version but the wiring harness was there.

 

So i was going to wire up the rear sensor off of this part of the harness but both the harness and the O2 sensor had female connectors, and the wires are different colors.

 

 

My question the O2 sensor i have has for wires one white one blue and two black.

 

My plug on the harness has Black red, black white, red, and red yellow.

 

Two questions

 

1) if i wire this wrong could it damage the computer or will it just throw a code?

 

2) are the two black ground wires interchangeable, from looking at the two plugs and the location of the wires I am pretty sure i have the white and blue wired the same but the two black wires on the sensors are all black no way to tell the difference between the two.

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[ChrisA]

Why plug it in? It does nothing but give status updates regarding the Cat health which you aren't running.

[Brian129]

Why plug it in? It does nothing but give status updates regarding the Cat health which you aren't running.

So it doesn't throw a check engine light that would be always on.
Then how would you tell if a new code popped up and there was an issue that needed to be addressed.

[ChrisA]

So it doesn't throw a check engine light that would be always on.
Then how would you tell if a new code popped up and there was an issue that needed to be addressed.

 

The light doesn't stay on if it is not there.   The light comes on primarily for emissions equipment failures. Just about everything performance wise that it would come on for, like a misfire, you would feel. About the only emissions component in our system worth being concerned about (since you wouldn't feel an impact) would be the Tank Pressure Sensor & Check Valve. Shouldn't be too much of a concern unless your exhaust is routed or cracks in a manner that heats the fuel tank excessively. That said, these sensors are starting to fail on the 99+ and Mazda has discontinued the part[s], so it is difficult to find a replacement. Thus, we really ought to have a rules change to allow the removal of the emissions system, including EGR. Their functional purpose in a race car is nil and there is no performance gain from removal, so let people remove this failing clutter from the cars. 

[B(Kuch)Kucera45]

It will throw a CE light. The 02 measures the waive form through the cat,I know the cat isn't in but the ECM will see no waive form and set the CE light on. Remember it measures the waive form from the AF sensor to the 02 sensor with or without the cat.

Frank it could cook the ECM if you get the power and ground hooked up wrong,same thing if you cut the wires while the key is on,so be careful !

[ChrisA]

Guess I wasn't too clear... The light won't be on if the light is not there. Removed mine years ago.

[FTodaro]

It will throw a CE light. The 02 measures the waive form through the cat,I know the cat isn't in but the ECM will see no waive form and set the CE light on. Remember it measures the waive form from the AF sensor to the 02 sensor with or without the cat.

Frank it could cook the ECM if you get the power and ground hooked up wrong,same thing if you cut the wires while the key is on,so be careful !

I decided to just get the right 02 sensor with the male plug. the front plug in has a female connector and the rear a Male connector. I could not safely figure out the rewire as the color code of the wires was not matching up between the 2000 and the 99 that i had as a spare. So all is good for me.

 

I do make the effort to hook up the rear o2 sensor so that it will only throw a cel when it is showing a problem.

[NPiekarski]

Frank- Not sure if it will help. On my last 99-00 I built with the calif. emissions, I opened up the wiring loom that runs to the front of the motor (the one that runs on the top of the engine next to the intake runners by the cam cover) and pulled the front o2 sensor plug and wiring back. There is enough wiring and you can hook this main (primary) o2 plug up to the down pipe sensor. The second o2 I made a bracket and tucked it in the wiper cowl area to keep it grounded. Worked great, no cel's.

[FTodaro]

Frank- Not sure if it will help. On my last 99-00 I built with the calif. emissions, I opened up the wiring loom that runs to the front of the motor (the one that runs on the top of the engine next to the intake runners by the cam cover) and pulled the front o2 sensor plug and wiring back. There is enough wiring and you can hook this main (primary) o2 plug up to the down pipe sensor. The second o2 I made a bracket and tucked it in the wiper cowl area to keep it grounded. Worked great, no cel's.

Nice, the 2000 I am doing is also a California emissions, but it also had the rear harness hookup and I went off of that.

[NPiekarski]

Yes, mine had 3 o2 connectors as well, 1 on the front of the exh man, 1 on the bottom of the big coffee can cat, and one under the drivers seat. I used both underhood connections, just mearly relocated the front manifold O2 connector to the rear for the down pipe and tucked the 2nd one up in the cowl.