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Discussion Starter #21
Tank, what are the voltage readings on each of the 4 pins of your O2 bank 1 sensor 1 ? The O2 sensor heater circuit should have Battery voltage on pin D , and a controlled path to ground via the ECM on pin E , both must be tested with the engine running.
With all the rain and garbage weather I haven't been able to get to it.

Heres this for now though

Screenshot_20200515-224808_Torque (Lite)_1589598573810.jpg Screenshot_20200515-224816_Torque (Lite)_1589598561589.jpg Screenshot_20200515-224915_Torque (Lite)_1589598552481.jpg Screenshot_20200515-224915_Torque (Lite)_1589598552481.jpg Screenshot_20200515-224703_Torque (Lite)_1589598583239.jpg
 

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Discussion Starter #22 (Edited)
Replaced battery, got better.
Few days later would barely run.
Changed oil, filter gurgled when I pulled it out. Odd.
Oil looked decent smelled normal. Almost 6k miles, I added one quart around 3500 miles. Drained almost 5qts. So in almost 6k miles I burned around 1qt, happy with that.
Car is running without any issue, smooth quiet, not one hiccup. I'm sure it will return in a month or so, it seems as everytime I change the oil it runs excellent for the first 2k miles or so, then starts to degrade. I supposed I stick to my gut and change the oil every 3k miles.
In the meantime I ordered both o2 sensors, throttle body and camshaft position sensor. Just gonna replace it all, parts were $200
 

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I replaced the 100k mile O2 sensors in my 5.3 Tahoe and picked up 1.9 mpg.
No codes and they appeared to be fine, getting another 1.9 mpg on average and getting to 18 mpg is a big deal.
Now my O2 sensors get changed with the spark plugs that I normally do at 80k miles.
 

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Discussion Starter #24
I replaced the 100k mile O2 sensors in my 5.3 Tahoe and picked up 1.9 mpg.
No codes and they appeared to be fine, getting another 1.9 mpg on average and getting to 18 mpg is a big deal.
Now my O2 sensors get changed with the spark plugs that I normally do at 80k miles.
Just confused, that's why I'm just gonna replace em. 100k miles out of them is good enough. I get they monitor the engine, and if they read off it could be the cat, a different array of sensors, or the o2 sensors themselves. Really just seems to point nowhere hence why I'm replacing a few things. Fingers crossed this helps in one way or another. Supposed to deliver tomorrow so hopefully I get everything replaced by mid week
 

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My fuel mileage loss in my Tahoe confirms just because they are not reporting a issue doesn't mean they are OK.
Sensors could be functioning at the edge of the failure threshold trigger and appear OK.

Front sensor is the primary closed loop sensor controlling fuel mixture, to me if my mileage improved that much means my cats have been getting over fueled and over worked for a while now. A couple of $35 sensors way cheaper than a couple of CA spec. cats. .

Yes you can get crazy and look at / monitor the waveform of the sensors feedback but who has time to go through that for a cheap part that IMO is now a maintenance item.
 
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