P0174 code trim issues

[zmann96]

I have a 2003 Yukon SLT 4 x 4 SLT 5.3L it's been coding for a long time and now I need an inspection. The lights been on and it's failed emissions. I have installed 4 new 02 sensors and it's coding quicker now after I clear with scanner than before. It's bank 2 that's the problem according to my scanner. I tried to see if my power brake was leaking air, I squeezed off the hose but the trims remained the same. I've checked for manifold leaks and had replaced the MAF and have cleaned it since. I noticed that the LT trim on bank 2 doesn't change it's at 25 really high. wondering if I got a bad sensor? I took a photo of the trims on my scanner at idle ( 600 RPM) and at 1500 RPM. anyone have some ideas?

 

[zmann96]

I have a 2003 Yukon SLT 4 x 4 SLT 5.3L it's been coding for a long time and now I need an inspection. The lights been on and it's failed emissions. I have installed 4 new 02 sensors and it's coding quicker now after I clear with scanner than before. It's bank 2 that's the problem according to my scanner. I tried to see if my power brake was leaking air, I squeezed off the hose but the trims remained the same. I've checked for manifold leaks and had replaced the MAF and have cleaned it since. I noticed that the LT trim on bank 2 doesn't change it's at 25 really high. wondering if I got a bad sensor? I took a photo of the trims on my scanner at idle ( 600 RPM) and at 1500 RPM. anyone have some ideas?

View attachment 250396 View attachment 250397

The top photo is at 1500 RPMs other is at Idle

 

[Fless]

That's a lean condition, probably a fairly large vacuum leak. Is the air intake tube tight and sealed? Anything else loose that would allow unmetered air in? Have you tried using some propane or carb cleaner around the intake gasket to see if the engine smooths out in certain areas?

Could also be other things, and I'll let others chime in.

 

[zmann96]

I've checked all connections but haven't done the propane. I'll try that Thank you for your input

 

[zmann96]

My concern is that bank 2 LT is registering 25 and doesn't change

 

[Fless]

That's the highest it will read. It's banging against the ceiling.

 

[Fless]

Here's one video on using the propane. There are plenty of others. He gets into the propane method around 3:00.

 

[afpj]

You mentioned bad sensor. I don't remember if the wire lengths are different between left and right but you might want to switch the sensors and see if the other bank starts reading lean. Can you graph the sensor voltages and see that they're performing properly? Another issue that could cause persistent high positive fuel trims at idle and higher rpm is a fuel issue iirc. Are your fuel injectors functioning properly on bank 2? You would expect faulty fuel injector function to make it run rough. Just throwing out ideas. Otherwise as stated above a massive air leak as possible, but only have it on bank 2 suggest the intake manifold section.

 

[zmann96]

You mentioned bad sensor. I don't remember if the wire lengths are different between left and right but you might want to switch the sensors and see if the other bank starts reading lean. Can you graph the sensor voltages and see that they're performing properly? Another issue that could cause persistent high positive fuel trims at idle and higher rpm is a fuel issue iirc. Are your fuel injectors functioning properly on bank 2? You would expect faulty fuel injector function to make it run rough. Just throwing out ideas. Otherwise as stated above a massive air leak as possible, but only have it on bank 2 suggest the intake manifold section.

Good Idea to switch sides. It has been only bank 2. My scanner won't graph. I'm guessing the injectors are fine, I replaced all of them. The engine runs really well and smooth. I'll check and do the propane test all around the manifold. Thanks for your input