Check engine light came on found the code and a lean condition was found by the computer

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)

https://repairpal.com > obd-ii-code-p0174
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)

https://www.yourmechanic.com > Articles
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

https://obd2pros.com > dtc-codes > p0151
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 ...

https://www.samarins.com > diagnose > p0171
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 ...

The check engine light is on to tell you the computer has found a problem that will affect performance, gas mileage, or emissions.
Such as the code 171 you asked about.
Code 171 is for the fuel mixture on bank one being too lean. The O2 sensor is telling the computer the fuel mixture is too lean and the computer can not make it rich enough.

gtford64,

P0171 indicates the computer has detected a "lean engine condition". Sorry to say you couldn't have gotten a worse code. By that I mean there are sooo many things that can cause a P0171
However I'll just run down a few of the more common causes:

1 - Look for any obvious vacuum leaks around the engine area. Vacuum leaks will definetley
cause a lean condition which will trigger a check engine light and code P0171
Especially check around the PCV system and where the EGR valve mounts to the intake.



2 - Check your oxygen sensor wiring to make sure it is not chaffed and shorted. This will force a
lean condition and set P0171. O2 sensors are located on your exhaust system pipes and
manifold.





3 - A constant or intermittent engine miss will trigger this code. Check for fouled or shorted
spark plugs or weak spark plug wires.

4 - Low fuel pressure will also trigger P0171. Check your fuel pressure if thats possibe. If it's low,
check to make sure your fuel filter is not restricted. Otherwise, you may have a weak fuel
pump!



Try these tips first.If not successful, we'll take it 1 step further. Good luck!


.

It means that the computer is getting a lean reading from the oxygen sensor. That can be caused by a vacuum leak letting in too much unmetered air, or it can be caused by a clogged fuel injector or low fuel pressure. The computer tries to compensate by adding more fuel. It can add up to around 25% more fuel. If that doesn't solve the lean condition, it sets a code for "too lean". Your job is to look for vacuum leaks because that's the most common cause. Also, check for any deterioration or cracking in the air duct that runs from the air filter box to the throttle body. ANYWHERE that air can get into the engine that hasn't first been measured by the MAF sensor will cause a lean condition.

Something odd about what you posted. An engine that is running lean shouldn't be using a lot of fuel. Lean is when there isn't enough fuel going into the engine. Two other sensors that regulate fuel flow are the map sensor and throttle position sensor. Temp sensor generally would cause a rich condition but I'd test that too. Be sure to check for vacuum leaks at the manifold and lines as well as fittings... A vacuum leak will give the O2 sensor a lean reading...seeing that, the computer will try to compensate by adding fuel. Clearing codes can change the way it's running but as soon as the computer runs through it's internal diagnostics it will turn the light back on if there is a problem.

Hi, a Ford P0171 is a LEAN code for cylinder bank 1, and P0174 is a LEAN code for cylinder bank 2. These codes commonly occur on many Ford vehicles, and are set when the powertrain control module (PCM) sees the air/fuel mixture is running too lean (too much air, not enough fuel).
When the Check Engine Light comes on, either one of these codes, or both, may be found when a code reader or scan tool is plugged into the vehicle diagnostic connector. IF the vehicle is driven long enough, typically both codes will be set.
A P0171 lean code for bank 1 is the cylinder bank on the RIGHT (passenger) side of the engine on Ford vehicles with a V6 or V8 engine and rear-wheel drive.


A lean fuel condition may exist if the engine is sucking in too much air and/or the fuel system is not delivering enough fuel. If bad enough, a lean fuel condition may cause lean misfire, a rough idle, hesitation or stumble when accelerating, and/or poor engine performance.
Unmetered air can enter the engine through a vacuum leak, a dirty airflow sensor that is not reading airflow accurately, an EGR valve is not closing and is leaking exhaust into the intake manifold, an EGR valve that is allowing too much flow (because the EGR differential pressure sensor that monitors EGR flow is faulty and is under-reporting EGR flow).
If the problem is not enough fuel, the underling cause may be a weak fuel pump, restricted fuel filter, leaky fuel pressure regulator or dirty fuel injectors.

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.
Thanks.

It means your O2 sensor has detected a lean condition, solutions to the problem can be found at this link http://www.obd-codes.com/p0171

Check for vacuum leaks. ie, vacuum lines them selves, the rubber tube that runs from the air filter to the throttle body. If it has a plastic intake manifold, possibly the rubber port seal gaskets between it and the engine. Lean codes are set when the PCM isn't monitoring all the air coming into the engine (vac leak) or low fuel pressure.

P0171 code is described as: lean condition bank 1, oxy sensor 1. If your vehicle is a 4 cylinder, which I believe it is.. you have got a lean air/fuel mixture being found by the ecm(computer).This can be caused by several things. The first of which is a possible vacuum leak at or near the intake manifold. This can also be caused by a MAF(Mass Air Flow) sensor problem or even by something as simple as a clogged fuel filter. This lean condition could also be the cause of the P0420 :described as a catalyst efficiency problem. It would be best to have the vehicle taken to a reputable repair facility that is capable of engine performance diagnostics and have them run tests for these codes. The gasket you mention is most likely a valve cover gasket not the head gasket and would not cause these codes. Although you should have this leak fixed before it becomes a problem.

Hope this helps..