Engine light on mercury mountaineer code PO 174 PO 171 how do i fix it......

Question edited for clarity.
Question moved to model category.

The check engine light alerts you that you have a problem that needs attention and then you connect a code reader scan tool and it gives you numbers. Those number tell the problem and how to fix. They are called DTCs (Diagnostic Trouble Codes). Garages will normally read the codes for you for free in the hope of getting the work. Or you can get a cheap code reader yourself.

I have the FIXD scanner which sends the information to an app on my smartphone.

https://www.google.com/search?q=fixd+scanner&

DTC Codes

https://www.google.com/search?q=2005+Mercury+Mountaineer+DTC+codes

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Fault codes are there for a reason. Fuel injection engines were designed in the 80's to reduce pollution and protect the ozone layer. a malfunctioning fuel injection engine will cause pollution. Replace all bad sensors. Your engine should reset itself. in turn will run better, efficient and improved performance.

Is the check engine light on? Mountaineers are bad about developing vacuum leaks which will lean the engine out and cause it to stumble at idle while in gear. Check for p0171 and p0174 codes.

fuel pump is possible. Have you fixed this yet?

should have told you when checked?

Have the codes scanned for your engine computer to see what subsystem is causing the engine light to go on. One can do this for free at many parts stores.

No, just go to Autozone, they will pull codes for free.

My husband had the same problem with his 02 Mountaineer about 6 months ago. I read somewhere that if you take WD40 & spray the door locks it should stop. We tried it & so far it's worked. Good luck!

the gas cap is the most common if u can reset code do so and if code comes back then need to check-- the fuel lines -purge valve and vent -also the canister--- for cracked disconnected damaged lines

Go to the local parts store, have them check the codes (they will do this for free usually). It will tell you what sensor needs to be checked/replaced. Once the part is replaced, it will clear on its own. They can also reset the code, but it will come back if the trouble persists.