Saturn vue 2002 aed v6 not passing inspection test

Question edited for clarity.
Question moved to model category.

As a general rule, with a laterally positioned V6 , Bank 1 is always closest to the firewall Bank 2 is closest to the headlights.

Sensor 1 is ALWAYS the one in the Exhaust Manifold, and Sensor 2 is ALWAYS the one AFTER the Catalytic converter.

confirmed here

02 sensor "bank 1 sensor 1" - Saturn Vue

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The diagnostic trouble code (DTC) P0420 "Catalyst System Efficiency Below Threshold" is one possible outcome following the Catalytic Converter Monitor (test). This monitor is one of the last tests to be performed by the powertrain control module (PCM) because other failures in the system could compromise this test's result. Catalyst efficiency is tested by observing the oxygen sensor signals both before and after the catalyst. Before the catalyst, the signal should appear as a sine wave as it switches back and forth between rich (0.9 volts) and lean (0.1 volts). After the catalyst, the signal should be flat-lined on the rich side (about 0.7 volts). This is because a healthy catalyst will store oxygen and therefore remove the "lean" portion of the signal/waveform. If the signal after the catalyst still appears as a sine wave, the PCM concludes that the catalyst can no longer store oxygen and should therefore be replaced. In your specific scenario where a downstream (post-cat) O2 sensor was just replaced, I would theorize that this sensor had failed and was flat-lined. Then when it was replaced two things happened: 1.) the oxygen sensor began to work properly which allowed the oxygen sensor monitor (test) to complete, and 2.) the catalyst monitor then ran and used the new (accurate) sensor data to determine that the catalyst efficiency was below threshold. You can read more here: https://www.yourmechanic.com/article/p0420-obd-ii-trouble-code-catalyst-system-efficiency-below-threshold-bank-1-by-jamahl-walker

Bank 1 is generally the cylinder bank closest to the firewall. Bank 2 is the one closest to the radiator.
Sensor 1 is the one in the exhaust manifold.

If the OBD code says it is running lean, you find it is covered in black soot when you remove it. With the new one in, you may get a running lean code as it is burning the soot out. Reset the code, it is a false positive. Happened to me last week.

https://www.google.com/search?q=sensor+1+bank+2+on+a+2008+saturn+vue+3.5l+v6+location

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it would be because its a V6 so has two banks set at 60 degrees too each other follow this u-tube link as gives an excellent view of why
Timing Marks Saturn Vue 3 0 Litre V6

code p0128 indicates a mechanical fault ( could be the thermostat stuck open)
code p0174 -system too lean -bank2 ===causes --intake /exhaust leak--fuel pressure/pump--injectors--AIR system--hose connection/s
code po171 refers to system too lean bank 1 same as po174 with the HO2S sensor being the culprit. As to all being related . only by way of the o2 sensors
code p0442 is not connected to the first 3 as it is in a different section of the fuel system

DTC P0171 - System Too Lean (Bank 1)
Basically this means that an oxygen sensor in bank 1 detected a lean condition (too much oxygen in the exhaust). On V6/V8/V10 engines, Bank 1 is the side of the engine that has cylinder #1.

Note: This DTC is very similar to P0174, and in fact your vehicle may show both codes at the same time.

According woth your previous tasks, inspect all vacuum and PCV hoses, replace if necessary.

there are 2 sensors in the system
one is a heated oxygen sensor (HO2S) in the exhaust manifold / pipe before the cat converter that reports the exhaust gas composition to the ECM so that fuel/ air ratios can be adjusted
if that one is faulty it is most likely the reason for running lean or rich
the second sensor is the oxygen sensor (O2) which is after the cat converter and reads the results of the cat converter cleaning the exhaust
you may have to replace both the sensors to get a clearance or replace the cat converter as well as the HO2S unit

If your engine light is coming on, then there is a code somewhere in the computer,it may be a pending code.Its possible your computer is bad. Have your computer tested.

I had exactly the same problem .Mine was corrected with replacing the O2 sensors .The sensors cost less than $30 each but cost about 20 mins labor per sensor .So if you got an honest mechanic the total cost will be around $130 .

Your vehicle’s computer system has self-testing capability. When the computer senses that there is a problem with some of the components it stores the correspondent trouble code(s) in its memory and lights up the "Check Engine" or "Service Engine Soon" light to tell you that there is a problem and you will need to have the car diagnosed and repaired.