2002 Ford F150 Check Engine Light with Codes P0401, P0171, and P0174 - Causes and Repair Costs
I recently purchased a used 2002 Ford F150 less than a month ago, and the check engine light has come on. The vehicle is displaying three diagnostic trouble codes: P0401, P0171, and P0174. I'm looking for information on what these codes mean, what repairs are needed, and an estimate of the associated costs to fix the issues.
The issue in my case was a broken L-shaped vacuum hose located on the engine side, near the left front (closest to the windshield) under the air intake ram. This component is known to fail over time and can cause misfires and fuel trim issues leading to P0171/P0174 and P0401 codes. A replacement part costs around $6 at AutoZone and can be easily installed. There are several YouTube videos available that demonstrate the repair process step-by-step.