P0171 - System Too Lean

[Th0r]

I'll check the header gasket. It is copper so there is a chance it would need retorqued, but I certainly don't hear anything. I'll plug the tailpipe and hook an air line into an O2 bung and to if I can hear any leaks.

The more I think about it the more I think the issue isn't with the O2. The fact that the slow response codes came back as soon as I unplugged the heaters tells me that the O2 is functioning fine. Once plugged back in it reads, drops the slow response codes and soon after sees a lean issue. I tested 2 difference sensors and they both acted the same way. We smoked the intake and there were no leaks. If I don't find any exhaust leaks I'll try a MAP sensor I guess.

[comanche]

Yep, check for exhaust leak first.

If nothing found, see if you can post a screenshot of your complete data screen.

We'd need to know all kinds of stuff...
O2 sensor info over time, idle
Map sensor voltage over time, idle
Coolant temp sensor voltage over time, idle
TPS

Etc

We can look for abnormalities.

Still.... it does sound like the O2 sensor is reading a false lean code.
Which the PCM would compensate for by adding fuel.
If there was a lot of false air, the PCM would add lots of fuel.

Do you have a chip? I thought the max short-term compensation for fuel trim in GM was +35%...... +49% just doesn't make sense for a stock GM vehicle.
MAF voltage over time, idle

[Th0r]

I torqued the header down, and was actually able to get a full turn on the wrench on two of the bolts at the drivers side.

No more codes! I really hate it when everything is a simple fix that I over looked, but love it when it costs me nothing to fix it haha.

[Vic28]

well good for you, hope that solved it.

[comanche]

What are your fuel trim numbers looking like now?

[Th0r]

I don't remember, but the tech that was helping me out said everything checked out when I brought it back in. I haven't borrowed a scanner to see for myself.

[comanche]

Cool. Sounds good.