[Gmecm] One wire oxygen sensor to four wire

[David Allen]

  Here is some Real-World experience.  Converting from a 1-wire (non-heated 
with sensor signal grounded through the exhaust manifold) to a 4-wire 
(heated with isolated sensor ground) works very well if you are having 
grounding or heat issues.
  My car has 1228746 ECM, which had a 1-wire sensor in the manifold in its 
original car.  My car doesn't have a hole in the manifold for a sensor so I 
welded in a bung in the exhaust pipe where te 2 manifolds wye together. Like 
this; the grounding conditions and thermal environment weren't very well 
suited to the 1-wire sensor.  Using a 4-wire unit keeps the sensor online 
even at idle, and the isolated ground cleans up the signal.
  The signal wire follows the original path to the ECM.  The Signal Ground 
wire, is grounded at the lug where all the ECM sensor grounds are bolted.
  The heater is controlled with the fuel pump circuit (only active when 
engine running).  One wire is grounded to the engine block, the other is 
powered (through its own fuse) from the fuel pump relay.
  AutoZone part # 15702 Bosch 4-wire sensor is what I used. It's a standard 
switching-type (narrow-band) sensor which produces a signal identical to the 
1-wire sensors.
  Hope this helps!
David



----- Original Message ----- 
From: "Jon Dods" <jdods at bigpond.net.au>
To: <gmecm at diy-efi.org>
Sent: Tuesday, June 05, 2007 6:42 PM
Subject: Re: [Gmecm] One wire oxygen sensor to four wire


> I've been patiently waiting for a reply top this topic as I'm also looking 
> to change from a one wire to a 4 wire sensor.
>
> I was hoping for somebody with some real life experience in this area 
> might contribute some information however, in lieu of that, I will post 
> what I have learnt on this subject so far.
>
> Based on my research, I believe this would be ok provided the sensor was 
> replaced with the same general type.  Since the most commonly used sensor 
> is a zirconium dioxide sensor I'm going to assume that's the one used in 
> this instance.  These come in a number of varieties and sizes. Obviously, 
> you need to choose one, which is the correct size for your bung.  Beyond 
> that, my belief is that the only difference is the wattage and/or voltage 
> of the heating element.  This is where I get a little lost as I've read 
> that the heating element in some sensors must be current controlled by the 
> ECU while others can be just hooked up to 12V.   Perhaps someone with more 
> knowledge on this subject can clarify this..
>
> The zirconium dioxide sensor should produce an average of 450 mV (0.45V) 
> output if the engine is running at 14.7:1 air/fuel mixture and the sensor 
> is at operating temperature.  The key word there is average, as the output 
> should actually fluctuate from around 225mV to 675mV in cycles taking 
> about 1 second to complete a full cycle.
>
>
>
> Regards,
>
> Jon.
>
> ----- Original Message ----- 
> From: "Mike Hudson" <sonoma at shaw.ca>
> To: <gmecm at diy-efi.org>
> Sent: Sunday, June 03, 2007 8:27 AM
> Subject: [Gmecm] One wire oxygen sensor to four wire
>
>
> Hi
> My setup is a full TBI system from a 91Chevy G20 including TBI intake and 
> HD TBI cylinder heads sitting on a 83 350/5.7 block.
> A 3 wire oxygen sensor doesn't have a wire for sensor ground, it uses the 
> o2 sensor body for the ground return path.
>
> I welded in a bung for the o2 just below the connection between the 
> exhaust manifold and the exhaust pipe. The ground for the o2 sensor would 
> have to go through that connection which is not the cleanest ground path. 
> That's why I would like to go with the four wire.
>
> The 4 wire has one wire for: o2 ground, o2 signal, heater positive and 
> heater ground.
>
>
>
>
> I was thinking of using something like a AC ASF-75 or NTK 21006(Narrow 
> band)
>
> Will the output from the 4 wire o2 output the same voltage at the same AFR 
> as the 1 wire sensor (Narrow band) ???
>
> Does anyone know which year and model vehicle the ASF-75 was used on?
>
> Thanks...
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