[Gmecm] One wire oxygen sensor to four wire

[Jay Vessels]

Hi there!

I've used 3-wire sensors (AFS-74) to replace 1-wire before; the 4-wire 
has a sensor ground as well as a heater ground.  I see no reason why an 
AC 4-wire NB sensor won't work in place of a 1 or 3 wire one.

The heater on a NB isn't ECM-controlled.  You could devise all sorts of 
schemes to drive the heater, but powering it any time the key is in On n 
or Run is sufficient (Start as well, if you like, though it's not likely 
to matter much).  If you want to minimize the heater "on" time when the 
engine is not running, you could power it via relay triggered by the 
fuel pump circuit.

A wideband sensor, now that's a completely different beast...

Jay Vessels
1982 Chevrolet S-10 Sport, 2.8V6 TBI
1984 Chevrolet S-10 Blazer Sport, 2.8V6 (TBI pending)

Jon Dods wrote:
> 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...
> _______________________________________________