01 nissan sentra- check engine light on found codes-p0171 system to lean bank 1 p0172 system rich bank 1 exhaust smells like raw fuel vehicle does stall sometimes only at idle at stop lights

Sensors come in different qualities and pricings. Some cheap ones made in Mexico fail in a few days. Always buy OEM quality sensors.

Your code is incorrect fuel mixture, sensor says running lean so it is dumping extra fuel.

Fuel Trim System Lean Bank 1

The code is thrown when the oxygen sensors detect that there's not enough oxygen in the exhaust system. This is commonly referred to as a "lean" condition.
The vehicle's ECM will add more fuel to the mixture in order to bring the air fuel mixture where it needs to be for optimal combustion. It also throws the code P0171 to let you know that it has done this.


Here are the typical symptoms that something is wrong when you have code P0171.

• Mileage- may or may not suffer depending on how much the air fuel mixture has changed.
• Misfire- If the air fuel mixture has gotten too far from factory specs, this can cause the Sentra to misfire.
• Idle Issues- With the air/fuel mixture altered, the vehicle can idle erratically as the computer compensates to keep the engine running.

https://www.google.com/search?q=Nissan+Sentra+code+p0171

Ideally you need an auto electrician with a pro grade scan tool...

DTC P0171: Fuel Trim System Lean Bank 1
DTC P0172: Fuel Trim System Rich Bank 1
DTC P0174: Fuel Trim System Lean Bank 2
DTC P0175: Fuel Trim System Rich Bank 2

Circuit/System Description
The engine control module (ECM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. Fuel delivery is controlled differently during Open Loop and Closed Loop (CL). During Open Loop, the ECM determines fuel delivery based on sensor signals without heated oxygen sensor (HO2S) input. During CL, the ECM adds HO2S inputs and level of purge to calculate the short and long term fuel trim (FT) adjustments. If the HO2S indicates a lean condition, the fuel trim values will be above 0 percent. If the HO2S indicates a rich condition, the FT values will be below 0 percent. The short term FT values change rapidly in response to the HO2S voltage signals. The long term FT makes coarse adjustments in order to maintain an optimum air/fuel ratio. A block of memory cells contain information arranged in combinations of engine RPM and engine load for a full range of vehicle operating conditions. The long term FT diagnostic is based on an average of cells currently being used. The ECM selects the cells based on the engine speed and load. The FT diagnostic will conduct a test to determine if a rich failure actually exists or if excessive vapor from the evaporative emission (EVAP) canister is causing a rich condition.
If the ECM detects an excessively lean condition, DTC P0171, P0174 sets. If the ECM detects an excessively rich condition, DTC P0172, P0175 sets.


DTC P0017: Crankshaft Position (CKP) - Exhaust Camshaft Position (CMP) Correlation Bank 1

Circuit/System Description
The engine control module (ECM) uses the crankshaft position (CKP) sensor and the camshaft position (CMP) sensor pulses to monitor the correlation between the crankshaft and camshaft position. The crankshaft reluctor wheel consists of a 60-tooth pattern with 2 teeth missing for a reference gap. Each tooth is evenly spaced 6 degrees apart, except for the reference gap. The camshaft reluctor wheel has 4 teeth, 2 narrow and 2 wide. The 4 trailing edges of each tooth are evenly spaced 90 camshaft degrees apart. As the crankshaft rotates with the CMP actuator in the home or parked position, the ECM expects CMP sensor pulses to occur 36 crankshaft degrees before top dead center (BTDC) at cylinder number 1, and every 90 camshaft degrees thereafter.

P0172 LEXUS - System Too Rich Bank 1
Possible causes
Faulty front heated oxygen sensor
Ignition misfiring
Faulty fuel injectors
Exhaust gas leaks
Incorrect fuel pressure
Faulty Mass Air Flow (MAF) sensor
https://www.autocodes.com/p0172_lexus.html

P0171 ; Fuel Trim System Lean (Bank 1)
P0174; Fuel Trim too Lean (Bank 2)
fuel trim is system to modify injector pulse if system go lean it will go rich when the system is too much lean and is max.rich it code
look for 02 sensor bank 1 and 2 data
hope it helps

PO 171 Bank 1 too lean
PO 174 Bank 2 too lean
Why ?
The front O2 Sensors need to be replaced at
100,000 miles or sooner, if they have actually failed
They are reading too lean because the system is too
rich & the computer is driving the fuel trim or injector
pulse lean, thus the codes or failed sensors, yes both
Have to check fuel trim with a scan tool
Have to check fuel pressure
Have to check there are no leaking injectors
Have to check for Vacuum Leaks from the intake
all the way to the exhaust converter
Your working a rich condition keeping in mind the system
is driven lean
You look at fuel trim short & long,sort of a past history
of events
May want to look at converter temps also
The converters won't last long if you have or has
a rich condition from fuel or cylinder misfires
Now the spark plugs can't be over 3 years old
& no mifires,get that out of the way before working
the O2 issues

You have big problems here, I suggest you go to the provided links and read about these fault codes and then hire a good technician.
Ford P0171 P0174 Lean Codes

P0172 OBD II Trouble Code System Too Rich Bank 1 YourMechanic Advice

https://www.obd-codes.com/p0175


P0304 OBD II Trouble Code Cylinder 4 Misfire Detected YourMechanic Advice

P0171 System Too Lean Bank 1
P0172 System Too Rich Bank 1
P0173 Fuel Trim Bank 2
P0174 System Too Lean Bank 2

OK, that's a partial list of codes, the fuel delivery is controlled by the oxygen sensors, so it's possible that something in that area could be causing your problem.

However, it could also be clogged fuel injectors that can't deliver enough fuel to the cylinders compared to the air that is pulled into the engine.

Try some fuel injector cleaner for that poured into the gas tank.

How does it run?
Does it miss at all?

P0171 indicates a lean condition. The most common cause of this is a defective mass air flow sensor. Also check if any vacuum leaks.Replace MAf sensor,if cleaning the MAF does not help.
OBD II P0172 Fuel System Too Rich (Bank 1).P0172 - System Too Rich (Bank 1) Essentially this DTC means that an oxygen sensor in bank 1 detected a rich condition.
When the code says that the Fuel System is "too rich," it means that the computer has been subtracting more and more fuel, which is called Long Term Fuel Trim. Ideally, the Long Term Fuel Trim should be close to 1 to 2 percent. When a code P0172 is set, it means that the Fuel Trim is anywhere from -15 percent to as low as -30 percent compensated. When this happens, the computer knows that there is an improper condition in the control of the Fuel System.


Thanks.

p0172 is--system to rich ( bank 1). an oxygen sensor on bank 1, detected a rich condition ( to little oxygen in exhaust ) v6-v8 - v10 engines, bank 1 is the side of the engine that has # 1 cylinder. causes could be a vacuum leak in a hose, a dirty or bad maf sensor, or fuel pressure or delivery problems.

those codes are for lean engine condition look for vac leaks at the back of engine to the pcv valve could hear hissing noise with engine running also check egr valve to be stuck open also when was last fuel filter changed? hope this helps .