1998 silverado codes p0171/p0174 what do they mean

Question edited for clarity. It is P-Zero 0, not P-oh O.
Please always include 'year make model' first 3 words, or it it is difficult to answer and some vehicles are slightly different or more precise and will show known issues.

P0174 - OBD-II Trouble Code Fuel System Too Lean (Bank 2)

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When a vehicle has the fault code P0174, it means that computer can no longer automatically adjust the mixture between air and fuel. Code P0174 applies to V ...

P0174 OBD-II Trouble Code: System Too Lean (Bank 2)

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Code P0174 indicates that there is a lean condition detected by the Engine Control Module (ECM). A lean condition will be created if there is too much air, and ...

P0151 Code - What Does It Mean & How To Fix It - OBD2PROS

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A P0151 code is caused by an ECM (Engine Control Module) receiving a signal indicating the O2 sensor for bank 2 sensor 1 has failed to increase the voltage ...

Code P0171 - System Too Lean: Symptoms, causes, common ...

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Jul 10, 2021 - The OBDII trouble code P0171 - System Too Lean (Bank 1) means that the engine air-fuel mixture is too lean, or there is too much air and too ...

P0300 - random misfire , P0171 & P0174 lean code's . All of this means you could have a bad vacuum leak ,low fuel pressure ,clogged fuel filter , Mass air flow sensor problem .
Ford 150 P0171 P0174 Trouble Codes vacuum leak water test
Low fuel pressure causing P0171 and P0174 trouble code

Did you verify the sensors were faulty before you replaced them ? Code 1345 means the signal from each sensor is not in sync with the other. That means one sensor signal is out of sync, or there is a problem with the timing chain.
Codes 171 and 174 deal with the issue of the fuel system being too lean on both banks or heads. You could have compression or fuel problems that would cause those codes.
A mechanic would use a scanner to monitor data from the sensors and try to figure out whats going on.

P0171 Means system is to lean on bank #1. P0174 Means system to lean on bank #2.

P0171 means: System too lean (Bank 1) P0174 means: System too lean (Bank 2). Sounds like your injectors are not getting enough fuel.

are the codes p0171 and p0174? p0171 system too lean (bank #1) p0174 system to low ( bank # 2) o2 sensors will go in pairs.

This is usually an oxygen sensor, replace the O2 sensor located above the catalytic converter before replacing the evaporator purge canister.

code P0171 P0174?? sorry these are not nissan codes but the code readers own codes so return to where the reading was done and ask them

P0171 System too Lean (Bank 1)
P0174 System too Lean (Bank 2)

If a car has a check engine light on and has P0171 and P0174 codes stored, the most likely cause is a vacuum leak. These codes are set by the car’s computer when it sees too much oxygen in the exhaust. Excessive oxygen readings in the exhaust will set lean codes. This does not mean that the oxygen sensors are defective. It is a common mistake for people to replace oxygen sensors when lean codes are present. Just because the code is related to oxygen sensor readings, it doesn’t mean that the oxygen sensors are bad. If both of these codes are stored this means that both banks of the engine have excessive oxygen in the exhaust. If the oxygen sensors are replaced it’s most likely that the same codes will reappear. It is very uncommon for two oxygen sensors to fail at the same time.

Therefore the most likely cause of P0171 and P0174 codes is a vacuum leak. The source of a vacuum leak can be one of many things. The most common cause of a vacuum leak is a leaky hose. Vacuum hoses over time can become dry and brittle. The rubber deteriorates and can leak causing a vacuum loss. Many times a leaky vacuum hose can be found by listening for a hissing sound. A large vacuum leak can even make the car run rough at idle. In some cases it will not idle without feathering the gas pedal.

Look on the passenger side of the intake at the rubber elbow attached to the big black plastic tube and then to the intake manifold. Make sure it is not sucking shut and maybe a small hole in the bottom of it.