: These letters can indicate specific characteristics of the engine, such as the cylinder head design (DOHC - Double Overhead Camshaft, SOHC - Single Overhead Camshaft), the number of valves, and fuel system type (fuel injection, carburetor, etc.). The exact meaning can vary, but in general, it points to the engine's configuration.

Locate the stepper motor (often a small black unit with a yellow or white plastic arm/gear).

: Moisture or poor pin tension at the actuator's plug disrupts the reference voltage signal.