1 wire to 3 wire O2 Sensor

Nad_Yvalhosert said:

Not sure when or why GM changed but I've always thought the ECM got better readings (combination of both banks) from the Y, than from only one side...

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Maybe so, only IF one or more cylinders on the right bank are misbehaving. IMHO one O2 sensor for the entire engine doesn't give you enough data for AFR control and troubleshooting, hence the improvement made in 96, huh?

Nad_Yvalhosert said:

The exhaust manifold has the flat section where the bung would be drilled and threaded. But its solid and original.
The OE y-pipe has the bung, right at the Y on the passenger side, and the 1 -wire pigtail comes right out the the harness & shield that holds the wires to the starter.

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That is weird, I knew 95 was a transitional year but, I didn't know that was part of it. I'm curious, anyone else have a 95 who can chime in on their O2 sensor's location?

PlayingWithTBI said:

You don't need to cut the connector with this setup.

www.amazon.com/ACDelco-AFS74-Original-Equipment-Heated/dp/B000C9VTRC/ref=sr_1_3?dchild=1&keywords=acdelco+afs74&qid=1634063397&sr=8-3

www.amazon.com/Michigan-Motorsports-Heated-Harness-Adapter/dp/B0141VHZ6U/ref=sr_1_1?dchild=1&keywords=michigan+motorsports+22300&qid=1634063344&sr=8-1

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Thanks for that. Wish I'd seen it a year ago. I had an extra 4-wire O2 sensor, so I ordered a matching 4-wire pigtail. It'll end up OK, but more work that what you've linked-to.

PlayingWithTBI said:

IMHO one O2 sensor for the entire engine doesn't give you enough data for AFR control and troubleshooting, hence the improvement made in 96, huh?

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Not so bad as you might think. You're sampling two cylinders running on the right-side injector, and two cylinders running on the left-side injector.

So, yeah, you've got no idea what's happening on the other bank if there's a problem, but the basic fueling should be OK.

Hey, having misfire detection would also be nice...but that also didn't show up until OBD II.

Where do you suggest connecting the power for the O2 heater? Obviously, it needs to be "Hot" when the key is turned to "Run" Hot in "Crank" is probably a bonus. But it needs to be a dead circuit in "Accessory" and "Off".

Here's the pigtail that fits my 4-wire O2 sensor. The wire colors are different from what the sensor uses, but it's easy to figure out what does what by looking at the position in the connector
body.
www.amazon.com/gp/product/B074F3VWJP/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I tied the two ground wires together, heater ground and sensor ground--crimped and soldered to a black 12-gauge extension wire, sealed with black adhesive-lined heat shrink tubing, and added a ring terminal on the end. It's on the thermostat housing stud with some of the other ground wires.

Added a one-wire Weatherpack connector to the purple signal wire, plugs into the stock harness just like the pigtail you linked-to above.

I'm not thrilled with the idea of soldering into the power wire for the HEI, but unless I get a better idea that's where it's going. The red wire got a 16-gauge extension also in red, crimped, soldered, and sealed with red heat-shrink tubing that has hot-melt adhesive on the inside. Then I attached a fuseholder (ATC), and that'll get attached to whatever power source I select.

Drove it about 15 miles; even without the heater powered, I got valid readings once the exhaust heated the sensor. It was sometimes but not always falling out of closed-loop at traffic lights.

95 k2500 one wire sensor just ahead of cat, 95 end of obd1. 96 and onward OBD2, emissions set a new tougher standard. Pre and after cat sensors. Pre for O2 signal for pcm. Post for cat health monitoring. Heated sensor faster response, emissions control, rather than waiting for it to come up to operating temp.

Schurkey said:

Where do you suggest connecting the power for the O2 heater? Obviously, it needs to be "Hot" when the key is turned to "Run" Hot in "Crank" is probably a bonus. But it needs to be a dead circuit in "Accessory" and "Off".

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Can someone answer this.
My 1999 5.7 Vortec's O2 sensor heaters are fed from the same fuse that serves the MAF sensor and EVAP. With ignition on but without engine running - will that circuit time-out? Or stay hot until the key is turned back?

PlayingWithTBI said:

You don't need to cut the connector with this setup.

www.amazon.com/ACDelco-AFS74-Original-Equipment-Heated/dp/B000C9VTRC/ref=sr_1_3?dchild=1&keywords=acdelco+afs74&qid=1634063397&sr=8-3

www.amazon.com/Michigan-Motorsports-Heated-Harness-Adapter/dp/B0141VHZ6U/ref=sr_1_1?dchild=1&keywords=michigan+motorsports+22300&qid=1634063344&sr=8-1

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I'm running the same setup on mine. I tapped the power from the pink/black stripe wire from the fuel pump fuse. I started out with it driver's side manifold and my wideband in the y-pipe. That works fine as long you're running TBI. Didn't work well at all with MPFI. I had to move the NB down to the y-pipe also.

Pinger said:

Can someone answer this.
My 1999 5.7 Vortec's O2 sensor heaters are fed from the same fuse that serves the MAF sensor and EVAP. With ignition on but without engine running - will that circuit time-out? Or stay hot until the key is turned back?

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The "circuit"--meaning the fuse--will almost certainly stay live as long as the key is turned to "Run" or "Crank".

I believe that the computer controls the ground on the heater in the O2 sensor. So the computer could turn the heater on and off as required--which means the heater likely wouldn't be operational with the engine not running. The service manual might have more insight.

This also means that I'm a little concerned about the heater life in the O2 sensor I just installed. That heater will be active as long as the engine runs, not turned on and off based on sensor temperature. But what do I know?

arrg said:

I tapped the power from the pink/black stripe wire from the fuel pump fuse.

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I ended up connecting to the HEI power wire. Never occurred to me to use the fuel pump circuit.

I don't think either of us will have a problem; I have the sense that the heater doesn't draw much power.

They can draw 10 amps.

Using a relay would take the load off whatever circuit you tapped into.

Schurkey said:

I believe that the computer controls the ground on the heater in the O2 sensor. So the computer could turn the heater on and off as required--which means the heater likely wouldn't be operational with the engine not running.

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Just to clarify, the early ECMs didn't control the heated O2 - there weren't any, originally just a 1 wire O2. I'm running mine off the ignition switch (fused of course) but, a relay fused and fed from the battery, excited by the fuel pump would work fine. I'm also running my WBO2 from the same switch - 2 years and no issues, so far

Frank Enstein said:

They can draw 10 amps.

Using a relay would take the load off whatever circuit you tapped into.

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Holy crap. I put a 5 amp fuse in the fuseholder for my O2 heater; I better check to see if it popped.

Michigan Motorsports pigtail wire harness uses THIN wire for that. Which is why I figured they wouldn't draw much power. I think it's 16 gauge at most, more-likely 18 gauge.