Hello again, still having problems with the 171 code fault.
Originally when the scanner was used both 171 & 174 codes were observed. The infamous pcv elbow was changed first, although the old one was not leaking. Both exhausts manifolds were very bad and were replaced along with the EGR pipe. Since then with the truck connected to a large but slow reading computer, we observed that only the 171 code is now present. Important to note that o2 sensor for bank 2 at times would flat line and then recover. Also the voltage to the MAF at idle was noted as low as .3V to .8V.
My question is if the o2 sensor is only intermittently operating would it trigger the check engine lite. Also would a faulty/dirty MAF also do the same thing?

 

All these function need to work full time.
A no signal condition from the Ox Sensor is a fault.
It will affect the fuel tables.
The short term fuel tables uses the sensor signals in real time to adjust running fuel injection levels.
The signal is used by the long term tables to keep the fuel system variable for overall load changes.
The mass air signal also adds to the fuel level calculation because it represents the amount of air at any given time that needs the correct amount of fuel to maintain air to fuel ratios.
After all, air is what runs the engine. The small amount of fuel injected only consumes the air to cause the resultant exhaust gas to expand.
No Ox signal normally causes the system to use a fixed rich point for fuel and should generate a code just from that fault if in any length of time.
All most sounds like there is a wire harness issue.
Good luck.

 

POINT OF ORDER
The code scheme is Pnnnn, where the first n is almost always 0 or 1, occasionally 2, the second n defines the sub-component of the vehicle, and the last two n positions are the specific trouble spot.

P0300 is a generic code, Any vehicle that displays this code has trouble with the same subsystem on the car, in this case the Ignition System. P0300 means RANDOM MULTIPLE MISFIRES, P0301 is, MISFIRE CYLINDER 1, a 4-cylinder cannot display P0305 because that is a MISFIRE CYLINDER 5. P07nn is a transmission error. P01nn is an emission issue, such as a MAF error or Fuel Mixture/Ratio problem. P0171 is always FUEL RATIO LEAN BANK 1. The reason for Lean can change from one make to another, or even from one model to another, but in all cases the code always means the fuel mixture is lean.

P1nnn is a code that is unique to the automaker that the code appears on. Let's say that you have a BMW that makes a P1188/P1189, and a Ford that also makes P1188/P1189 codes, but the meaning of the code for BMW and for Ford does not have to be the same, as with the P0nnn codes that are generic. If you have a P1nnn code, then you have to find it for the car you are working on so you go in the right direction with your repair efforts.

P2nnn is an expanded set of generic codes. They are still pretty rare as not many automakers have implemented them yet. This code sequence is intended for future capacity that is just now starting to show up.

When listing your codes in the OBD II format, you should give them as P0nnn, P1nnn, and so on.

 

https://www.obd-codes.com/p0171