The Actuator B control motor is the designated electric driver for the auxiliary or 'B' bank of a split system. Working alongside Actuator A, this motor manages the passenger side of dual climate controls, or the second cylinder bank on V6 and V8 engines. By dividing control, the engine computer can balance intake airflow or cabin temperatures independently.
On variable intake manifolds, the Actuator B motor adjusts the runner valves on the passenger-side head. If this motor fails, bank two will run poorly under heavy loads, causing a rough engine feel and a P2009 or P2015 code. Just like the 'A' motor, it uses a position sensor to report its state back to the computer.
When replacing Actuator B, you must verify that the linkage moves freely by hand first. If the intake runners are stuck with carbon buildup, installing a new motor will only lead to it burning out. Cleaning the carbon deposits out of the intake manifold ports is necessary to make the repair last.