P0174

[George Owens]

Good afternoon to all. I have an 08 Tahoe with the 5.3 engine. Today my check engine light came on and I notice it was a little bit rough especially at idle it was fine yesterday this kind of came out of nowhere. I connected my scan tool and got the code P0174 I also took some pictures of the live data. I changed the upstream O2 sensor when I first got the car about a year and a half ago, I clean the MAF and the code is still there, I didn’t hear any vacuum leaks and all The hoses seem tight, any idea what this could be? Here are the live data pictures I took.

 

[swathdiver]

Bank 2 is a mess. Now with your TPS showing 22%, is that at idle? P0174 is a lean code for Bank 2. Your upstream O2 sensors should be cycling between 40 mV to 900 MV and STFTs and LTFTs 10% or less with 0% being optimum.

The Mass Airflow Sensor should be reading between 2-6 g/s at idle. Yours is showing different scale so you'll have to convert and see if its within that spec. What is the MAP sensor showing?

Fuel Pressure looks fine.

Vacuum leaks, exhaust leaks, faulty injector(s) and O2 sensors can cause this. Check all vacuum lines and air intake between filter and throttle body. Look up how to test intake gaskets for leaks using your scan tool.

Run a graph of your O2 sensors, all 4.

 

[George Owens]

Bank 2 is a mess. Now with your TPS showing 22%, is that at idle? P0174 is a lean code for Bank 2. Your upstream O2 sensors should be cycling between 40 mV to 900 MV and STFTs and LTFTs 10% or less with 0% being optimum.

The Mass Airflow Sensor should be reading between 2-6 g/s at idle. Yours is showing different scale so you'll have to convert and see if its within that spec. What is the MAP sensor showing?

Fuel Pressure looks fine.

Vacuum leaks, exhaust leaks, faulty injector(s) and O2 sensors can cause this. Check all vacuum lines and air intake between filter and throttle body. Look up how to test intake gaskets for leaks using your scan tool.

Run a graph of your O2 sensors, all 4.

The tps always read 20 something as long as I had it, I’ve read that if it was P0174 and another code I forgot then it could be the intake gasket, and I don’t know if the tool actually graphs, I just got it but I’ll try

 

[swathdiver]

The tps always read 20 something as long as I had it, I’ve read that if it was P0174 and another code I forgot then it could be the intake gasket, and I don’t know if the tool actually graphs, I just got it but I’ll try

I just recognized your avatar and realized it's been a while since we chatted. How've you been? Did you have this Tahoe back then?

That tool in the pictures says it will graph. So you have a P300, P0174 and a third, what is it?

 

[George Owens]

I just recognized your avatar and realized it's been a while since we chatted. How've you been? Did you have this Tahoe back then?

That tool in the pictures says it will graph. So you have a P300, P0174 and a third, what is it?

It was P0174 I’m sure p0300 has something to do with that and the other is saved P0174 and yes I’ve had this Tahoe for like a year and a half, I got it for Father’s Day last year

 

[swathdiver]

It was P0174 I’m sure p0300 has something to do with that and the other is saved P0174 and yes I’ve had this Tahoe for like a year and a half, I got it for Father’s Day last year

That's awesome. Yes, I figure that P300 is related. Now the quest is to see if it's a particular cylinder or those intake gaskets. Do you have a little blue propane cylinder with those little torches? You can let out some gas (unlit!) around the intake and watch a graph of the O2 sensors. If they react to it, you know it's time for gaskets. If not, have to look elsewhere.

 

[George Owens]

That's awesome. Yes, I figure that P300 is related. Now the quest is to see if it's a particular cylinder or those intake gaskets. Do you have a little blue propane cylinder with those little torches? You can let out some gas (unlit!) around the intake and watch a graph of the O2 sensors. If they react to it, you know it's time for gaskets. If not, have to look elsewhere.

You definitely lost me when

That's awesome. Yes, I figure that P300 is related. Now the quest is to see if it's a particular cylinder or those intake gaskets. Do you have a little blue propane cylinder with those little torches? You can let out some gas (unlit!) around the intake and watch a graph of the O2 sensors. If they react to it, you know it's time for gaskets. If not, have to look elsewhere.

You definitely lost me when you started mentioning propane cylinders and a little torches LOL but here is what the MAP looks like

 

[George Owens]

And if I did the conversion table right I am getting around 6.1 somethings GS for the MAF

 

[swathdiver]

You definitely lost me when you started mentioning propane cylinders and a little torches LOL but here is what the MAP looks like...

Those numbers look fine too.

You've seen or used these before right?

 

[George Owens]

OK and I think I see the problem I took a picture of all four sensors notice bank to censor one which I believe is the upstream I see that there is no power going to it ?

Those numbers look fine too.

You've seen or used these before right?

View attachment 213169

I have never even seen it before LOL but I took pictures of all 4 sensors notice how Bank 2 sensor 1 shows no power