Jeep Cherokee (XJ): Description and operation
DESCRIPTION This group covers the various standard and
optional power distribution components used on this
model. The power distribution system for this vehicle
consists of the following components: The power distribution system also incorporates
various types of circuit control and protection features,
including: Following are general descriptions of the major
components in the power distribution system. See the
owner's manual in the vehicle glove box for more
information on the features and use of all of the
power distribution system components. Refer to the
index in this service manual for the location of complete
circuit diagrams for the various power distribution
system components.
NOTE: This group covers both Left-Hand Drive
(LHD) and Right-Hand Drive (RHD) versions of this
model. Whenever required and feasible, the RHD
versions of affected vehicle components have been
constructed as mirror-image of the LHD versions.
While most of the illustrations used in this group
represent only the LHD version, the diagnostic and
service procedures outlined can generally be
applied to either version. Exceptions to this rule
have been clearly identified as LHD or RHD, if a
special illustration or procedure is required. OPERATION The power distribution system for this vehicle is
designed to provide safe, reliable, and centralized distribution
points for the electrical current required to
operate all of the many standard and optional factory-
installed electrical and electronic powertrain,
chassis, safety, security, comfort and convenience systems.
At the same time, the power distribution system
was designed to provide ready access to these
electrical distribution points for the vehicle technician
to use when conducting diagnosis and repair of
faulty circuits. The power distribution system can
also prove useful for the sourcing of additional electrical
circuits that may be required to provide the
electrical current needed to operate many accessories
that the vehicle owner may choose to have installed
in the aftermarket. DESCRIPTION
1 - LEFT FENDER All of the electrical current distributed throughout
this vehicle is directed through the standard equipment
Power Distribution Center (PDC) (Fig. 1). The
molded plastic PDC housing is located on the right
side of the engine compartment, just behind the battery.
The PDC houses up to fourteen blade-type maxi
fuses, which replace all in-line fusible links. The PDC
also houses up to twelve blade-type mini fuses, and
up to eight International Standards Organization
(ISO) relays (four standard-type and four micro-type).
The PDC housing is secured to a stamped sheet
metal bracket in the engine compartment by mounting
slots and tabs that are integral to the PDC housing.
The PDC mounting bracket is secured with two
screws to the right front inner fender shield above
the right front wheel house. The PDC housing has a
molded plastic cover that includes two integral hinge
tabs on the inboard side, and an integral latch on the
outboard side. The PDC cover is easily opened or
removed for service access and has a convenient fuse
and relay layout map integral to the inside surface of
the cover to ensure proper component identification.
A separate molded plastic B(+) terminal stud cover is
secured by two integral tabs and a latch to one end
of the PDC housing.
The PDC cover, the PDC housing lower cover, the
PDC B(+) terminal stud cover, the PDC relay wedges
and the PDC relay cassettes are available for service
replacement. The PDC main housing unit, the fuse
wedges, the fuse cassette and the bus bars cannot be
repaired and are only serviced as a unit with the
headlamp and dash wire harness. If the PDC main
housing unit, fuse wedges, fuse cassette or the bus
bars are faulty or damaged, the headlamp and dash
wire harness unit must be replaced. OPERATION All of the current from the battery and the generator
output enters the PDC through two cables and
eyelets that are secured with a nut to the PDC B(+)
terminal stud located on one end of the PDC housing.
The PDC B(+) terminal stud cover is unlatched and
removed to access the battery and generator output
connection B(+) terminal stud. The PDC cover is
unlatched and opened or removed to access the fuses
or relays. Internal connection of all of the PDC circuits
is accomplished by an intricate combination of
hard wiring and bus bars. Refer to Power Distribution
in the index of this service manual for the location
of complete PDC circuit diagrams. DESCRIPTION
1 - POWER DISTRIBUTION CENTER All vehicles are equipped with an Ignition-Off
Draw (IOD) fuse (Fig. 2) that is removed from its
cavity in the Power Distribution Center (PDC) when
the vehicle is shipped from the factory. Dealer personnel are to remove the IOD
fuse from the storage
location and install it into PDC fuse cavity 16 as part
of the preparation procedures performed just prior to
new vehicle delivery.
The PDC has a molded plastic cover that can be
removed to provide service access to all of the fuses
and relays in the PDC. An integral latch and hinge
tabs are molded into the PDC cover for easy removal.
A fuse layout map is integral to the underside of the
PDC cover to ensure proper fuse and relay identification.
The IOD fuse is a 15 ampere mini blade-type
fuse and, when removed, it is stored in a plastic fuse
holder formation that is molded into the underside of
the PDC cover. OPERATION The term ignition-off draw identifies a normal condition
where power is being drained from the battery
with the ignition switch in the Off position. The IOD
fuse feeds the memory and sleep mode functions for
many of the electronic modules in the vehicle as well
as various other accessories that require battery current
when the ignition switch is in the Off position,
including the clock. The only reason the IOD fuse is
removed is to reduce the normal IOD of the vehicle
electrical system during new vehicle transportation
and pre-delivery storage to reduce battery depletion,
while still allowing vehicle operation so that the
vehicle can be loaded, unloaded and moved as needed
by both vehicle transportation company and dealer
personnel.
The IOD fuse is removed from PDC fuse cavity 16
when the vehicle is shipped from the assembly plant.
Dealer personnel must install the IOD fuse when the
vehicle is being prepared for delivery in order to
restore full electrical system operation. Once the
vehicle is prepared for delivery, the IOD function of
this fuse becomes transparent and the fuse that has
been assigned the IOD designation becomes only
another Fused B(+) circuit fuse. The IOD fuse serves
no useful purpose to the dealer technician in the service
or diagnosis of any vehicle system or condition,
other than the same purpose as that of any other
standard circuit protection device.
The IOD fuse can be used by the vehicle owner as
a convenient means of reducing battery depletion
when a vehicle is to be stored for periods not to
exceed about thirty days. However, it must be
remembered that removing the IOD fuse will not
eliminate IOD, but only reduce this normal condition.
If a vehicle will be stored for more than about thirty
days, the battery negative cable should be disconnected
to eliminate normal IOD; and, the battery
should be tested and recharged at regular intervals
during the vehicle storage period to prevent the battery
from becoming discharged or damaged. Refer to
Battery in the index of this service manual for the
location of additional service information covering
the battery. DESCRIPTION
1 - JUNCTION BLOCK An electrical Junction Block (JB) is concealed
behind the right cowl side inner trim panel in the
passenger compartment of the vehicle (Fig. 3). The
JB combines the functions previously provided by a
separate fuseblock module and relay center. The JB
serves to simplify and centralize numerous electrical
components, as well as to distribute electrical current
to many of the accessory systems in the vehicle. It
also eliminates the need for numerous splice connections
and serves in place of a bulkhead connector
between many of the engine compartment, instrument
panel, and body wire harnesses. The JB houses
up to twenty-seven blade-type fuses (three standardtype
and twenty-four mini-type), up to three bladetype
automatic resetting circuit breakers, and four
International Standards Organization (ISO) relays
(three standard-type and one micro-type).
The molded plastic JB housing has integral mounting
brackets that are secured with three nuts to
studs on the right cowl side inner panel below the
instrument panel. The right cowl side inner trim
panel is secured to a stud on the JB with a push nut.
A snap-fit fuse access panel can be removed for service
of the JB fuses and also conceals the push nut. A
finger recess is molded into the front of the fuse access panel for easy
removal, and a fuse puller and
spare fuse holders are located on the back of the fuse
access panel.
The JB unit cannot be repaired and is only serviced
as an assembly. If any internal circuit or the JB
housing is faulty or damaged, the entire JB unit
must be replaced. OPERATION All of the circuits entering and leaving the JB do
so through up to ten wire harness connectors, which
are connected to the JB through integral connector
receptacles molded into the JB housing. Internal connection
of all of the JB circuits is accomplished by an
intricate combination of hard wiring and bus bars.
Refer to Junction Block in the index of this service
manual for the location of complete JB circuit diagrams.Power distribution system
Power distribution center
Fig. 1 Power Distribution Center Location
2 - BATTERY
3 - POWER DISTRIBUTION CENTERIgnition-off draw fuse
Fig. 2 Ignition-Off Draw Fuse
2 - IGNITION-OFF DRAW FUSEJunction block
Fig. 3 Junction Block Location
2 - FUSE ACCESS PANEL
3 - RIGHT COWL SIDE INNER TRIM PANEL
Other materials:
Event Data Recorder (EDR)
This vehicle is equipped with an event data recorder
(EDR). The main purpose of an EDR is to record, in
certain crash or near crash-like situations, such as an air
bag deployment or hitting a road obstacle, data that will
assist in understanding how a vehicle's systems performed.
The EDR is d ...