Power and Ground Distribution: Description and Operation
Fig 1 Power Distribution Center:
POWER DISTRIBUTION SYSTEM DESCRIPTION
The power distribution system for this vehicle is designed to provide safe, reliable, and centralized distribution of the electrical current required to operate all of the many standard and optional factory installed electrical and electronic powertrain, chassis, safety, comfort and convenience systems.
At the same time, these systems were designed to provide convenient to access centralized locations for conducting diagnosis of faulty circuits, and for sourcing the additional current requirements of many aftermarket vehicle accessory and convenience items.
These power distribution systems also incorporate various types of circuit control and protection features, including:
- Blade-type fuses
- Cartridge fuses
- Automatic resetting circuit breakers
- Relays
- Flashers
- Circuit splice blocks.
The power distribution system for this vehicle consists of the following components:
- Power Distribution Center (PDC)
- Junction Block (JB)
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, use and operation of all of the power distribution system components.
POWER DISTRIBUTION CENTER DESCRIPTION
All of the electrical current distributed throughout this vehicle is directed through the standard equipment Power Distribution Center (PDC).
The molded plastic PDC housing is located in the left front corner of the engine compartment, just behind the battery. The PDC housing has a molded plastic cover that includes two integral latches, one on each side. The PDC cover is easily removed for service access and has a convenient adhesive-backed fuse and relay layout label affixed to the inside surface of the cover to ensure proper component identification.
The PDC housing is secured in the engine compartment on the outboard side with two screws to the left front inner fender shield, and with a screw on the inboard side to the left front inner wheel house.
The PDC cover is unlatched and removed to access the battery/generator cable input and output connection studs. The PDC is integral to the headlamp and dash wire harness, which exits from the inboard end of the PDC housing.
All of the current from the battery/generator cable connections enters the PDC through a 140 ampere generator cartridge fuse that is secured with screws just inside the inboard end of the PDC housing.
The PDC houses up to twelve maxi-fuse cartridges, which replace all in-line fusible links. The PDC also houses up to thirteen blade-type fuses (two standard-type and eleven mini-type), up to seventeen International Standards Organization (ISO) relays (five standard-type and twelve micro-type), two joint connectors (one eighteen-way and one twenty-eight-way), a forty-three-way engine wire harness in-line connector and a fuse puller. Internal connection of all of the PDC circuits is accomplished by an intricate combination of hard wiring and bus bars.
The cartridge fuses, blade-type fuses and relays are available for service replacement. The PDC unit cannot be repaired and is only serviced as a unit with the headlamp and dash wire harness. If the internal circuits or the PDC housing are faulty or damaged, the headlamp and dash wire harness unit must be replaced.
GENERATOR CARTRIDGE FUSE DESCRIPTION
A 140 ampere generator cartridge fuse is secured with two screws to the input and output bus bars within the Power Distribution Center. This cartridge fuse helps to protect the vehicle electrical system from damage that could be caused by overcharging and/or excessive electrical system current due to a faulty generator or faulty charging system circuits.
If a generator cartridge fuse fails, be certain to inspect and test the vehicle charging system before replacing the cartridge fuse and returning the vehicle to service. Refer to Charging System Testing for the proper procedures.
The generator cartridge fuse is available for service replacement. This cartridge fuse cannot be repaired and, if faulty or damaged, must be replaced.
Fig 2 Junction Block:
JUNCTION BLOCK DESCRIPTION
An electrical Junction Block (JB) is concealed behind the left outboard end of the instrument panel cover. The molded plastic JB housing has integral mounting brackets that are secured with two screws to the left instrument panel end bracket. The left end of the instrument panel cover has a snap-fit fuse access panel that can be removed for service of the junction block fuses. A fuse puller and spare fuse holders are located on the back of the fuse access cover, as well as an adhesive-backed fuse layout label to ensure proper fuse identification.
The JB combines the functions previously provided by a separate fuseblock module and relay center, serves to simplify and centralize numerous electrical components, and 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.
All of the circuits entering and leaving the JB do so through up to nine wire harness connectors, which are connected to the JB through integral connector receptacles molded into the JB housing. The JB houses up to nineteen blade-type fuses (two standard-type and seventeen mini-type), up to two blade type automatic resetting circuit breakers, the electronic combination turn signal and hazard warning flasher, and one International Standards Organization (ISO) micro-relay. Internal connection of all of the JB circuits is accomplished by an intricate combination of hard wiring and bus bars.
The fuses, circuit breakers, relays and flasher are available for service replacement. The JB unit cannot be repaired and is only serviced as an assembly. If any internal circuit or if the JB housing is faulty or damaged, the entire JB unit must be replaced.