System Lean Bank 1 and 2 Codes?

KEIKERMAN

MEMBER
2001 FORD F-150
V8
4WD
AUTOMATIC
105,000 MILES

The service engine soon light lit on my 2001 f-150 w/5.4 V8. I checked the code and it came up as a P0171 and P0174 (System Lean Bank 1 and 2 respectively). It also appears the when it warms up the RPMs tend to fluctuate. Thought it might be because the injectors need to be cleaned so I put a fuel additive in to get rid of any build up in the injectors and it appeared to improve the problem. The RPMs still fluctuate but not as bad. The truck does have a K&N Filter and Intake on it and have heard that sometimes it could cause the mass air flow sensor to get dirty and that this could be a cause of the problem. Is this possible, and could it be as simple as cleaning the Mass Air Flow Sensor?

1 Reply

MHPAUTOS

MECHANIC
31,938 POSTS

The P0171 and P0174 codes indicate a "System Lean Bank 1" and "System Lean Bank 2" condition, respectively, on your 2001 Ford F-150 with a 5.4 V8 engine. These codes usually point to a problem with the air/fuel mixture being too lean, meaning there is not enough fuel compared to the amount of air entering the engine. Here are a few potential causes and steps you can take to address the issue:

Check for Vacuum Leaks: Vacuum leaks can introduce extra air into the engine, leading to a lean condition. Inspect the intake manifold, vacuum hoses, and gaskets for any signs of leaks, such as cracks or loose connections. You can also use a smoke test to help identify potential vacuum leaks.

Clean or Replace the Mass Air Flow (MAF) Sensor: The K&N filter and intake system you mentioned can sometimes cause the MAF sensor to become dirty or contaminated. A dirty MAF sensor can affect the air/fuel mixture readings and trigger lean codes. Remove the MAF sensor and clean it using a MAF sensor cleaner. Be sure to follow the manufacturer's instructions. If cleaning doesn't resolve the issue, consider replacing the MAF sensor.

Inspect the Fuel System: While you mentioned adding a fuel additive to clean the injectors, it's also worth inspecting the fuel system for any other potential issues. Check the fuel filter to ensure it is not clogged and restricting fuel flow. You may also want to have the fuel pressure tested to ensure it is within the manufacturer's specifications.

Check the Oxygen (O2) Sensors: Faulty O2 sensors can sometimes provide inaccurate readings, leading to a lean condition. If the sensors are old or have high mileage, they may need to be replaced. Consider replacing both upstream (before the catalytic converter) and downstream (after the catalytic converter) O2 sensors for optimal performance.

This guide

https://www.2carpros.com/articles/repair-lean-mixture-codes-p0171-or-p0174-on-some-manufacturers can help as well

Please go over these guides and get back to us.