4 wire O2 sensor

[CDeeZ]

Hey people,

It's been a while since I replaced my OE style 1 wire O2 sensor. I think it's probably time to replace it since they tend to get "lazy" with use.

Enter brainstorming session:
I'm thinking that I want to try a 4 wire O2 sensor this time for the benefits a heated O2 can yield.

I think that wiring it up should be a piece of cake. I'm thinking the wires should go like this: One wire for the signal to the ECM, one wire is the ground for that circuit to the ECM (just as a backup incase there are problems with the O2 grounding through the body of the sensor itself), and the last two wires are for the heater element circuit, one of which will go to a +12V switched power source, and the other is just another ground wire for the heater element circuit...

Do I have this right? Are there 2 grounds with a 4 wire? One for the ECM signal circuit and the other for the heater element circuit? Seems simple enough but someone please correct if necessary..

I'm planning on using ACDelco AFS75 as my new 4 wire O2 sensor..... At only 32 bucks it seems like a fair deal, plus it's actually ACDelco rather than some goofy brand noone has heard of.

[JeepsAndGuns]

You are correct, you will have the signal wire, then a ground for the sensor, then two for the heating element. 1 to power, the other to ground, doesnt matter witch one.

[RobertISaar]

100%.

amazon shows it for 32.29 with free shipping.... awesome.

[FSJ Guy]

You will love a heated O2 sensor!!! You'll be in closed loop in no time! Also, it won't get cold when driving in rain or through slushy snow.

[dyeager535]

Why the four wire vs. the three wire AFS-74?

I remember doing some reading on either thirdgen or diy-efi about the various O2 sensors that GM used, and as I recall, the AFS-74 was the "best" heated to use with the late 80's/90's stuff. Something to do with the way the sensor operates in regards to it's output voltage.

[EagleMark]

IIRC the three wire uses one wire to ground the power circut.

Four wire has a ground for power circut and ground for O2 sensor signal. Since the GM ECM already has a O2 signal circut tied into ground there is no need for four wire O2 sensor...

[RobertISaar]

know of a factory application for the 3 wire? i can confirm what it uses the 3 wires for then.

while the signal ground can be redundant, the ECM does use an individual ground circuit for reference.

[dyeager535]

here's one app:
Blazer 4x4 (Full size) 1994-1994 V8-350ci 5.7L F/I Vin K

Sorry for the formatting here.

1994 V8-350ci 5.7L F/I Vin K Four wire seems pretty cheap though, at $32 if that's an AC Delco part, it's probably substantially less than the AFS-74. Only used 94-95 according to delco

[RobertISaar]

colors might be different, but for a 94 blazer 5.7:

two white wires are used for the heater circuit, black wire is used for the O2 signal(goes to pin A10), and the ground reference is pin A12(if you were using a 4 wire, you would connect the O2 signal ground there).

[EagleMark]

Well we just bought a 3 wire for my sons 16197427 conversion I think he looked it up as 1995 Chevy truck 4l60E.

My LT1 is a four wire 1994 Chevy Camaro, Corvette, Caprice or Buick Roadmaster.

Just from memory of doing harness's I remember seeing a pin for O2 ground seperate from other sensors but tied to same ground wire in harness from factory.