Group 28 Design and Function
Optional Engine Speed Limit
Optional engine speed limit is the maximum speed at
which the engine can be operated with the vehicle at
zero road speed and the PTO mode engaged. Optional
engine speed limit parameters can be programmed with
the VCADS Pro tool.
Optional Vehicle Speed Limit
Optional vehicle speed limit allows for an optional switch
to limit vehicle speed. Typically, this switch is operated
on the vehicle by someone other than the driver, such as
a garbage collector who rides on the back of the vehicle.
Optional vehicle speed limit parameters can be pro-
grammed with the VCADS Pro tool.
Note: Basic vehicle speed limit is set by the EECU.
Shut-Down Request
Optional engine shut-down request is made via a remote
mounted switch (the ignition switch is the basic engine
shut-down request). After the VECU receives the shut-
down request, the request is sent to the EECU via the
J1939 Control Link. Shut-down request is enabled using
the VCADS Pro tool.
Note: The engine shut-down request function should not
be considered or used as an emergency shut-down.
Torque Limit
Torque limit 1 and 2 are used to limit drive line torque.
Torque limit parameters can be programmed with the
VCADS Pro tool.
Engine Fan Request
The VECU receives the request for engine fan operation
from either a manual switch or a high pressure A/C re-
frigerant switch. The VECU then transfers the request to
the EECU via the J1939 Control Link.
Brake/Clutch Status Switches
The VECU recognizes the position of the brake, clutch,
and parking brake. Various VECU functions (i.e. cruise
control or PTO) operate only when these switches are in
the proper position.
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