P0174 Ford Explorer: Understanding and Fixing the System Too Lean Trouble Code


Today, I want to discuss a common issue that causes P0171, P0174 Bank 1 & 2 lean codes in Ford Explorers with the 4.0-liter SOHC engine.

In a previous video, I showed how a split PCV tube was causing abnormal fuel trims due to oil saturation. This time, we’ll look at another frequent issue that triggers lean codes in these vehicles.

The intake seals in these Ford Explorers can sometimes cause problems, particularly in cold weather. However, after checking the mileage and discovering that the vehicle had recently undergone an oil change, I immediately suspected the culprit.

During the oil change service, the air filter is typically inspected. However, the tube for the ventilation in the PCV system, which is prone to slipping out, often gets overlooked. This oversight can lead to unmetered air entering the engine, causing it to receive more air than it expects, thus triggering the lean codes.

When there is a leak in the intake tube or a vacuum leak in the intake vacuum hose after the mass airflow sensor, the engine’s air measurements become inaccurate, resulting in the lean codes.

By reconnecting the tube, we can observe the PCM’s reaction. Disconnecting the tube affects short-term fuel trims, O2 sensors, and the bass baro. Reconnecting the tube prompts it to readjust, correcting the fuel trims and restoring the vehicle’s performance to normal.

Resetting the PCM allows the vehicle to learn and update its settings, ensuring proper air and fuel calculations. This simple fix can resolve drivability concerns and check engine light issues related to lean codes in Ford Explorers with the 4.0-liter engine.


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