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I'm going to add a air/fuel gage and I picked up a Bosch 13942 sensor. Can someone tell me how to determine which wire is for what? It's a 3 wire(heated)unit and it has one black wire and 2 white wires. I'm guessing the black is a ground but one white wire has to be 12V power and the other goes to the gage.

Thanks!
 

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The two white wires are your heater...doesn't matter which is + or - it is just a resistive element. The black wire is your signal wire. Signal ground is through the sensor case. You aren't running any type of ceramic coated headers are you?

Also of note...don't solder your wire connections to the sensor, this is one (and just about only) place to use crimp on connectors. The sensor needs an atmospheric oxygen reference and is designed to allow a small amount of oxygen to permeate down the wires to the sensor. Soldering can melt the insulation and/or fill up the minute passages with solder or flux.
 

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Originally posted by Corey872:
The two white wires are your heater...doesn't matter which is + or - it is just a resistive element. The black wire is your signal wire. Signal ground is through the sensor case. You aren't running any type of ceramic coated headers are you?

Also of note...don't solder your wire connections to the sensor, this is one (and just about only) place to use crimp on connectors. The sensor needs an atmospheric oxygen reference and is designed to allow a small amount of oxygen to permeate down the wires to the sensor. Soldering can melt the insulation and/or fill up the minute passages with solder or flux.
Yes, I am running coated headers. Is that a problem? I'm not going to weld the threaded bung into the headers but in the collector. That's why I got a heated sensor. From what I understand the heated sensor doesn't have to be so close to the exhaust port.

I was planning on using Posi-Lock connectors or make a weather pac connector.
 

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I think you're fine with the location...sorry I wasn't being too clear with my explination on the ceramic. If you have ceramic headers with built-in bungs, sometimes the ceramic is enough to cause intermittent ground problems with the sensor. In that case a 4-wire sensor works great because it has an additional wire for sensor ground to insure proper connection. If you are welding into the pipe, you should be OK with the ground going through additional hardware back to the chassis.


With the connectors, you just don't want to use anything that will goop up the connection...silicone, solder, flux, etc...air has to be able to permeate down the insulation. There is a great deal of info on O2's at

http://www.parttrackers.com/library/1/24/27/


Specifically about the insulation...

"A mention of the waterproof feature that's present on numerous recent versions is appropriate here. All it means is that the reference air isn't picked up through a vent right at the sensor itself where water and other contaminants are plentiful. Instead, there's a sealed sleeve of insulation that runs up into the harness, or even all the way to the PCM, before it opens to the atmosphere. Since only a tiny amount of reference air is needed, enough will flow between the gaps in the stranded wires inside the insulation. You can get into trouble if you solder these cables because it wouldn't take much flux, solder, or melted plastic to block those essential gaps. "
 

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I had to change from 1-wire to 4-wire because of the headers so I just went to a junkyard and got the mating connector for the O2 sensor. Then, when you buy the O2 you have the connector and it's easy to install.

On a side note, Don't expect the O2 to work right at idle or low throttle. It may but then again it may not. I'm fairly certain mine still tends to read a little richer than it really is. The 1-wire was causing me big problems because it would go full-rich as it cooled while idling or coasting/driving slowly. Then, I'd really have to put some heat into it to get it back. Just going to 1500-2000rpm or so driving in town didn't do it. It took higher rpms for a bit of time to get it back. This causes some really stupid self learning by the computer.

Peter
 
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