jeepguy553

Possible O2?
I found this tonight playing around on the Summit web catalog...looking for ways to blow my tax return. I thought it might work as a WB...
I am probably an idiot and don't know what I am talking about.

justme

I believe this is your standard heated narrow band.

brennanw

This is a 4 wire sensor. Two wires are for hot and ground and the third is for signal. But what is the 4th wire used for?

HaulnA$$

2 wires are for the heater (polarity not important) and 2 wires are for the signal, i.e. signal and signal ground. This setup is supposed to reduce signal noise to the ECM.

brennanw

Ah, ok. Thanks. Now when you say "signal ground" does that mean that the 4th wire can be run straight to ground? Or does it ground through the ECM?

HaulnA$$

Generally the O2 sensor signal ground is connected to ECM ground to reduce the chance of noise from entering the ECM. The shorter amd more direct the return current path for any signal, the less likely noise can be introduced, generally speaking.

brennanw

Ok, so I take it that this means the ECM must be specifically designed to run a 4 wire? The ECM is internally switching this wire to ground? Or could this be tapped into the ground wire running from the ECM to the body?

jeepguy553

Man, I opened up a can of worms, didn't I? Cool! This is great stuff guys!
Speaking of a 3-wire heated O2...how would I go about wiring one up with a TBI 8746 or 7747 ECM...or should I forget it and get a WB right off the bat?

brennanw

I'm using a 3 wire heated O2 on a 7747. It's a bosch 3-wire sensor for an '89 Ford Thunderbird (BOSCH #13942). The wiring for the three wire is very easy. The two white wires (heater wires) are for power and ground (doesn't matter which). The black wire is the O2 signal for the ECM.

JP84Z430HP

There is one of the grounds on the ecm that is designated as the O2 ground. You would want to run this wire to your O2's sensor ground wire. On the 1227747 that you're running brennan, it would be pin "D6", and it's a tan colored wire.

jeepguy553

Same one on an 8746...HMMMMM...got me thinking...can you see the smoke coming from my ears?

brennanw

Ah, Ok. Thanks! I looked it up in my wiring diagram and found the wire you're talking about. Pin D6 runs from the ECM to ground. So, from the looks of this I can just tap into this wire.

jeepguy553

Uhhh...no. I think you need to pull that wire from ground and connect it straight to the new O2 ground wire. That way, you eliminate the "noise" from the circuit like HaulnA$$ was saying.

brennanw

Ok, got it now. I'm a newb so I'm expected to say stupid things, right? It's a poor excuse but it's the only one I have.

jeepguy553

I'm still a noob too...don't feel bad. I say stupid stuff. When I first logged on this board, I didn't know the majority of the terminology and I took a few razzings...