power supply circuits in the event of a module failure.
The VPDM is located in the vehicle electronics bay,
behind the passenger-side dash panel. See
Fig. 11.5.
Depending on a vehicle’s specifications, the fuses
and relays installed and their locations can vary.
Each VPDM cover is illustrated with an image of the
fuse and relay layout for that vehicle. See
Fig. 11.7
for an example of VPDM cover map of fuses and
relays.
Both the VPDM and the sSAM are grounded at the
cab-side front wall. See
Fig. 11.5.
On vehicles equipped with a cab load disconnect
switch (CLDS), the BCA houses a contacting device
that can open to shut off power to high current loads.
The cab load disconnect switch (CLDS) is an op-
tional switch that can be used to open (turn OFF) or
close (turn ON) circuits between the battery and the
battery cable access box (BCA). It is described more
fully later in this chapter.
Cab Electrical and Electronic
Components
Pass-Through Bulkhead Connector
The pass-through bulkhead connector is where the
interior dash harness connects to the exterior chassis
harness. This provides a disconnect point for har-
ness service, testing, and replacement. It is located
on the driver-side front wall of the truck. See
Fig. 11.5.
Single Signal Detect and Actuation
Module (sSAM)
The single signal detect and actuation module
(sSAM) is the primary module in the electrical sys-
tem, combining chassis power distribution, cab power
distribution, and modular switch functions into a
single ECU. The sSAM does not contain fuses or
relays.
The sSAM reads input information from sensors,
switches, and databus messages, and drives output
and controller area network (CAN) messages. The
sSAM is located near the center of the cab behind
the lower dash panel. See
Fig. 11.5
Electronics Bay
The electronics bay contains the electronic control
units that control different vehicle features. It is lo-
cated on the passenger-side of the cab behind the
dash panel. See
Fig. 11.5 for its location in the cab
and
Fig. 11.8 for the location of ECUs in the bay.
f54731308/14/2020
Fig. 11.6, Example Fuse Labeling on BCA Cover
f54731208/14/2020
Fig. 11.7, VPDM Inside Cover Map of Fuses and Relays
Electrical System
11.4
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