P0171 check engine light

Error Codes
1

So I was driving my 2016 Escape like usual, and suddenly the check engine light comes on. The car starts acting weird, like it wants to stall, and the light blinks on and off. It felt like it might cut off completely, so I was trying to find a safe spot to pull over.

But then, out of nowhere, the car starts driving fine again.

I went to AutoZone to check the code, and the readout said something about the Power Train System. Specifically, it mentioned “Bank 1 System is too lean for a predetermined length of time.”

Can someone explain what that actually means? And more importantly, how much do you think it’ll cost me to fix this?

2

I had the same issue! My car had terrible gas mileage, rough idling, and even stalled when I stopped. Here’s what eventually fixed it for me:

  • Changed the engine air filter.
  • Used a fuel system cleaner (I went with Techron) in the gas tank.
  • Cleaned the MAP and air intake sensors.
  • Checked for loose air box parts or vacuum leaks in the tubes.
  • Replaced the spark plugs.

And with turbo engines, always use 93-octane gas from top-tier brands. After doing all that, my 2014 Fusion 2.0T was back to normal. Ford’s turbo motors seem to have this issue often.

3

@Drake
Thanks for sharing all those tips! I’ll be seeing my mechanic first thing Monday morning to get it sorted. Appreciate your advice. :blush:

4

In my experience, it’s usually a vacuum leak on the intake side. Could be a cracked hose, gasket, or some other component. Here’s how I’d diagnose it:

  1. Use a smoke tester to check for leaks—this is the safest method.
  2. If you don’t have that, spray brake cleaner around the intake and hoses while the engine is running. If the idle changes, you’ve found your leak.

Just be super careful with the brake cleaner—don’t spray it near the exhaust manifold, and definitely wear a face shield. Trust me, I’ve seen people lose their eyebrows doing this.

5

@Shai
Appreciate the advice! I’ll leave this one to my mechanic. He said he has the tools to take care of it. Thanks for pointing me in the right direction!

6

That code could mean a lot of things, but the most common cause is unmetered air getting into the system—like a leak in the intake or vacuum hoses. Have it checked out soon before it gets worse.