With a Ford P0171 code, the first step is to get it properly diagnosed to figure out what is causing the engine to run lean. Commonly associated with error codes: P0174.Vacuum leaks – PCV hoses, vacuum hoses, intake manifold gasket.When these adjustments become too large, the Ford P0171 code is triggered. To keep the engine running properly, the powertrain control module (PCM) tries to compensate for the lean condition by injecting more fuel to the mixture in an effort to maintain the proper 14.7:1 ratio.

The lean condition can be caused by a vacuum leak, which introduces more air into the air-fuel mixture, or by a weak fuel system, which does not input enough fuel into the air-fuel mixture. Too much fuel and/or too little air results in the engine running rich setting a P0172 trouble code, while too little fuel and/or too much air results in the engine running lean resulting in a check engine light for the Ford P0171 code. Many people will replace the air-fuel sensor or oxygen sensor as soon as they get a bad reading, but the root cause can also be a dirty or faulty mass airflow sensor or vacuum leak, thus causing the O2 or MAF sensor to read differently to compensate.Ĭombustion engines run most efficiently when they maintain an air-fuel mixture ratio of 14.7 parts air to 1 part fuel. Diagnosis: It is important to complete the entire diagnostic process when diagnosing the Ford P0171 code.Repair Urgency: Get this code fixed as soon as possible to avoid damage to spark plugs, pistons, and catalytic converters.

Issue Severity: MODERATE– Extended driving with this code can cause internal engine damage.

P0171 definition : Bank 1 has too much air or not enough fuel.

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