2003 Yukon issues - SOLVED

[Fless]

Apparently auto-sensor does not like the word "p3gging" with an E... Let me revise previous post to use the term "pinning the fuel trim at maximum"...

You should have the ability to edit your initial post.

 

[ic455]

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)

 

[ic455]

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

 

[ic455]

Here's a YouTube link to the video

 

[ic455]

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

 

[Fless]

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.

 

[Fless]

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.

 

[ic455]

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.

 

[ic455]

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

Exactly! The lack of any codes related to fuel is what has had me stumped.

 

[Fless]

Well, once the fuel trims hit 25, plus or minus, it'll trigger the check engine light. So there's that.