2003 Yukon issues - SOLVED

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ic455

ic455

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Y'all are awesome, I will get the exact readings shortly, seems like everything hits the fan at once. The brands on parts I've replaced are mostly chinese‍♂️ but swapping things with my 04 yields the same results(on the stuff I've swapped, which hasn't been everything...yet)
 
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ic455

ic455

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I have some videos of my scanner but I can't upload mp4 I guess. Suffice to say I've discovered that the trims go positive LT and ST on bank one only. So positive that the graph line nearly disappears at the top. If I unplug any one injector on bank 1 it smooths out. So it appears I'm over fueling bank 1 after warm up. It appears to be random the amount of time it takes, this time was engine running about 26 minutes.
See vids below
 
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ic455

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Here's the O2 data that goes with the fuel trim data.
 

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Looks to me like your upstream O2 sensor on Bank 1 (driver's side, closest to engine) isn't switching, it's sticking around the lowest part of (what should be) its range of 100-900 mV. As a test you could swap the two front sensors to see if the issue follows to the other side, otherwise you may want to replace them; best to do them in pairs if possible. Recommend OE sensors.
 

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Looks to me like your upstream O2 sensor on Bank 1 (driver's side, closest to engine) isn't switching, it's sticking around the lowest part of (what should be) its range of 100-900 mV. As a test you could swap the two front sensors to see if the issue follows to the other side, otherwise you may want to replace them; best to do them in pairs if possible. Recommend OE sensors.

This is based on no engine codes that relate to the fuel system, like an O2 heater code.
 
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ic455

ic455

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Looks to me like your upstream O2 sensor on Bank 1 (driver's side, closest to engine) isn't switching, it's sticking around the lowest part of (what should be) its range of 100-900 mV. As a test you could swap the two front sensors to see if the issue follows to the other side, otherwise you may want to replace them; best to do them in pairs if possible. Recommend OE sensors.
Man, that's what I was thinking, too! I'm going to try replacing the B1 upstream and see where that gets me first, and go from there.
 

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