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-   -   single wire o2 conversion to 3/4 (heated) (

getnpsi 10-29-2008 02:40 PM

single wire o2 conversion to 3/4 (heated)
This was discussed on one of the other boards i frequent. Has anyone added this to their 1980s/1990s obd cars and experienced a smoother running during warmup? I think with the colder weather setting in the faster we can get into closed loop the better. My only question, is if the o2 heater is running off 12v or another voltage i have to find (or make) elsewhere in the car? I know that with a single wire sensor, the sensor housing itself is the ground like a spark plug, and it has it's own signal to carry back to the ecu.

some_other_dave 10-29-2008 03:24 PM

The three-wire O2 sensor will have the signal wire, a power wire, and a ground wire. Hook up those wires to the appropriate things and it should work nicely.

I don't recall if the ground wire is only used to ground the heating element (likely IMHO) or if it also grounds the O2 circuit itself. I think you'd get more variation in the reading with the heating if the ground wire was shared by the sensor and the heater, so I'm guessing that the sensor would still ground through the threads into the exhaust pipe.

I am less sure, but I think a four-wire sensor has heater power, heater ground, signal wire, and sensor ground wire.


getnpsi 10-29-2008 03:31 PM

After doing a search, i found that on those more modern vehicles, the ecu does the grounding. Im not sure which 4 wire systems have that property and which do not so i think im better off scoring a 3 wire. It's cheaper at the store anyway. I think i have some 3 wires used at home. Im going to install one of those and if my car behaves the same or better then great. if not then at least i have the oem plug installed and can replace with ease.

Dust 10-29-2008 06:52 PM


trebuchet03 10-29-2008 07:02 PM


Originally Posted by getnpsi (Post 69930)
My only question, is if the o2 heater is running off 12v or another voltage i have to find (or make) elsewhere in the car?

From my previous experimentation and failures.... Yes, it's 12V ;)

Red 10-29-2008 07:42 PM

12v ftw

metalshark 11-19-2008 03:32 AM

I can pretty much guarantee that the more wire running from the o2 sensor the better. looking into wideband o2 sensors I have found that they are used for the ecu or ecm to be able to control the Air to fuel ratio that way efficiency is at its peak.

its all depending on how much your willing to work on it.

never ground to an exhaust pipe unless you want a small fire under the hood the exhaust pipes reach over 600 degrees Fahrenheit.

getnpsi 12-01-2008 08:18 PM

o2 sensor is really stuck in the manifold. i have an o2 sensor socket but its a cheapo brand and really starts to bend when i apply a lot of force. Im not going to remove the radiator just to get my impact in there. It's not THAT important :)

Coyote X 12-01-2008 09:23 PM

It depends on the ECU if it is going to help anything with warmup smoothness. But if you do engine off coasting the 1 wire sensors cool down quick and take a few minutes to warm back up even if the engine is at full temp while driving easy. I would suggest using a 4 wire sensor and running the ground back to the ecu to get a lot more accurate signal. On an OBD1 Metro as soon as the water is over 110 degrees I think, and the sensor is reading the car then starts using it.

4 Wire Oxygen Sensor–

lot more info on switching to a 4 wire sensor there.

getnpsi 12-01-2008 10:05 PM

Yes, for the engine off coasting is why i was addressing the add-on. where i live, we do not get under 40 degrees during the day ever so many of you probably wonder why I even bother with additional "warm-up" techniques, but if i have free parts lying around why not.

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