2008 Ford Fusion P0016 Fault Code: Diagnosis and Repair Guide

I'm currently working on a 2008 Ford Fusion that has been fitted with a used engine. The vehicle runs reasonably well, but the check engine light remains on due to the persistent P0016 fault code. I've already replaced the crankshaft position sensor, but the issue persists. This model uses a timing chain, not a timing belt, and I'm unsure of the correct diagnosis or repair steps for this specific P0016 error. Any insights into how to resolve this would be greatly appreciated.