My 2010 4.0 v6 will throw a P0171 code every few months. The first time it happened, I took it to a shop. They told me it was the fuel filter and replaced it. The code comes back every few months. I’ve noticed it only pops up if I hit the gas hard. I’m guessing that could be a clue? What sort of tests should I do? Check the fuel pressure? Any help is appreciated!

 

so how many miles on the motor? could be the O2 sensor or MAF sensor. MAF sensor is easy to clean. O2 sensors wear out at 100k or 10yrs.

 

The truck has about 215k kms or 133k miles. I’ve been thinking it could be the o2 sensor. Is there a way to verify the sensors are working without just replacing them and hoping for the best? I’ve already cleaned the MAF sensor.

 

its a good idea to change the O2 sensors now. i think the right side is pretty easy you can get to it from the wheelwell, remove the tire. driverside is a bit harder. i use ForScan and a ELM bluetooth or wifi OBD sender. then you can check all sensors and etc.

 

Thanks for the reply! My scanner is not that fancy haha. I was just ordering some new fog lights from rock auto and threw in some bosch upstream o2 sensors. Probably good maintenance anyway. I’ll see how that goes! My only other guess would be the fuel pump getting old. Though, I think I’d have trouble starting the truck if that was the case?

 

ELM OBD reader is like $8 on Ebay and some of the apps are free. but you get a lot of info and you can compare to good info.

 

Maybe change the order to Motorcraft sensors?

 

bosch is what Ron D recommended ?

 

I didn't know that. Had I known, I would've gone with his recommendation.

At 18 years, I researched and bought Denos O2 sensors.
They OEM for Volvo and their afternarket sensors have worked fine.

I feel my fuel mileage has taken a hit and am considering buying Motorcraft sensors.
With my limited driving, gas mileage might not tell the story.

 

My O2 sensors had nearly 200 thousand on them and 22 yrs of use. I replaced my O2 sensors with Bosch last June and they have worked flawlessly. Bosch sensors are top shelf in my estimation.

 

I finally got the o2 sensors in. It was a bit of a pain in the ***, one was a little stuck. Hopefully this keeps my code away 🙏🏻

 

Now take it out and hit the gas hard as you mentioned in the first post.
P0171 is a lean code, so check for a vacuum leak.

 

The code came back :( Not sure what the next move should be. I’m thinking either get a nicer obd2 code reader with fuel trim readings or do a smoke test. Thoughts?

 

ELM 327 Bluetooth or WiFi Transponder eBay or Amazon. then look for an app I use FORScan or car scanner. I use my iPad. Or phone. You’ll gat lots of data

 

Thanks! I’ll check that out. I’m also thinking about getting a fuel pressure gauge and doing a test. I’ve heard of rangers getting a lean code when the fuel pump is getting weak.

 

Haha, now the code is gone. I didn’t even clear it this time. I just drove a few kms and it disappeared. What a pesky code.

 

If anyone see this in their googling, I have not seen the codes since I last posted. I kind of forgot about it. Knock on wood, it seems like the o2 sensors did it. I think it came back once after the new sensors. My best guess is, it was the computer relearning and adjusting to the new ones 🤷

 

The code's been out for 4.5 months. You can reasonably conclude your intake hoses are sound too.

The PCV valve is connected to the intake via an L-shaped run made of 2 pieces of plastic pipe and 2 rubber elbows.
When you change your PCV valve, inspect this piping.
It can be a "future P0171".

 

I'll keep an eye on that! I've read about it a lot in my research.

 

FYI: The PCV valve "quarter turns" into the rear of the left (driver's side) valve cover.
The grommet is built into the cover.
You DO NOT want to stress it or otherwise risk breaking it as a new cover is impossible to find.