Vehicle Power Distribution
WARNING
Do not attempt to modify, add, splice, or remove
electrical wiring on this vehicle. Doing so could
damage the electrical system and result in a fire
that could cause serious personal injury or prop-
erty damage.
Power Distribution Modules
The main power distribution module (PDM) is located
under the hood on the driver-side splash shield. See
Fig. 3.1. The PDM contains the circuit breakers and
fuses required to protect the vehicle cab circuits. The
label on the inside of the PDM cover identifies typical
set of fuses.
The powertrain PDM (PTPDM) is mounted in the en-
gine compartment near the main PDM. See
Fig. 3.1.
It controls power to the engine, aftertreatment system
(ATS), transmission, and other powertrain-related
circuits.
The auxiliary PDM is located on the cab back wall,
behind the driver’s seat. See
Fig. 3.2. The auxiliary
PDM may contain the auxiliary powernet distribution
box, the body lighting PDM, and the trailer PDM, if
so equipped.
Main Powernet Distribution Box
The main powernet distribution box (PNDB) is
mounted on the cab frontwall next to the bulkhead
module. See
Fig. 3.1. It supplies power to the
PTPDM and main PDM, and powers other vehicle
functions, including the clock. The label on the PNDB
fuse cover identifies typical circuits.
An auxiliary PNDB may also be located on the cab
back wall, behind the driver’s seat.
Load Disconnect Switch
WARNING
Turning the load disconnect switch to the OFF
position does not disconnect the connection be-
tween the battery and the starter. To work on the
vehicle safely, the negative leads must be discon-
nected from the battery.
The optional load disconnect switch (
Fig. 3.3)is
used to avoid excessive draw on the battery when
the vehicle is parked for an extended period of time.
When the load disconnect switch is set to OFF, it sig-
nals the PNDB to disconnect battery power to pow-
ertrain and accessory loads.
The load disconnect switch is mounted in one of two
locations:
•
inside the cab on the left side of the driver’s
seat;
•
on/near the battery box;
IMPORTANT: The ignition should be turned OFF
before using the load disconnect switch.
11/24/2010 f545704
1
2
3
4
1. Bulkhead Module
2. Powernet Distribution Box (PNDB)
3. Main Power Distribution Module (PDM)
4. Powertrain PDM (PTPDM)
Fig. 3.1, Power Distribution Module Locations
Electrical System
3.1
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