How do you diagnose a check engine light on 2004 f350?

To diagnose a check engine light on a 2004 F350, start by using an OBD-II scanner to retrieve the trouble codes stored in the vehicle's computer. These codes provide insight into specific issues that may be triggering the light. After identifying the codes, inspect related components, such as sensors, wiring, and hoses, for any faults or malfunctions. Finally, clear the codes and test drive the vehicle to see if the light reappears, confirming whether the issue has been resolved.