Xtool E2S User Manual page 23

Actuation test (Bi-directional control)
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Actuation test, also known as bidirectional control, is a generic term used to describe sending
and receiving information between one device and another. This function is used mainly to
judge whether these actuating components of the engine are working properly.
The vehicle engineers responsible for designing computer control systems programmed them
so a scan tool could request information or command a module to perform specific tests and
functions. Some manufacturers refer to bidirectional controls as functional tests, actuator
tests, inspection tests, system tests or the like. Reinitialization and reprogramming also can
be included in the list of bidirectional controls.
This function allows the device to send information to and receive information from, vehicle
control modules. For example, in the case of OBD II generic information Mode 1 (which
relates to data parameters), the scan tool user initiates a request for information from the
powertrain control module (PCM), and the PCM responds by sending the information back to
the scan tool for display. Most enhanced scan tools also can actuate relays, injectors and coils,
perform system tests, etc. Users could check the individual part to see what is working
properly by actuation test.