Running rich?

[99BB3500]

You know for a fact that one is throwing a code, two others are acting goofy with almost no voltage variation, and you're suspecting all of them are old.

Does voltage fluctuate in an open loop also, or just in a closed loop?

 

[Schurkey]

It fluctuates meaningfully in closed loop. It may or may not fluctuate in open-loop; when the computer decides the O2 sensor voltage is reliable (which may involve a timer, and/or other condition-sensing logic)--it goes into closed loop.

 

[stutaeng]

I can't remember of the top of my head. But the system is typically running richer under open loop. That's how the ECU is programmed; the system is not supposed to be collecting data from the O2s during closed loop until it reaches operating temperature and goes into closed loop.

I would just go ahead and check for ground and 12V+ at the sensor to make sure you don't have a wiring problem. It's a free/easy check. Here's other checks you can do: https://easyautodiagnostics.com/gm/2.2L/how-to-test-the-oxygen-sensor-2

Or if you don't want to mess with them, just replace them. Rockauto has the best prices on those. Also, I think you still need to look into why your fuel pressure seems low. That may or may not be a problem.

 

[99BB3500]

The issue with the fuel is either the injectors or FPR. The filter and pump are new. I may change the line just to change it.

 

[Schurkey]

The issue with the fuel is either the injectors or FPR.

You don't know that. Low fuel pressure can be caused by about a dozen things, and you haven't ruled all of them out, yet.

In fact, you don't even know that the fuel pressure IS low, since I don't see you reporting pressure-test results AFTER you changed the pump and filter.

DO NOT trust the fuel trim numbers. Fuel trim is determined by the O2 sensor signal, and we know your O2 sensors are fooked.

 

[99BB3500]

I can't remember of the top of my head. But the system is typically running richer under open loop. That's how the ECU is programmed; the system is not supposed to be collecting data from the O2s during closed loop until it reaches operating temperature and goes into closed loop.

Open loop the STFT are close to 0. When it goes into closed loop is when they move down to -10

 

[99BB3500]

So voltage fluctuates in a closed loop between .400 and .535 volts

edited because I was in wrong area of the scanner

 

[99BB3500]

Voltage went up when I was on the gas

 

[PlayingWithTBI]

I agree with @Schurkey. Looking at your log, I think your O2 sensors are getting lazy.

 

[stutaeng]

If one bank O2 is acting funny but the other looks normal, an easy check is to swap them and see if the problem switches to the other bank.

What does the other side look like?