JEEP YJ 1995 Service And Repair Manual

CHARGING SYSTEM
CHARGING SYSTEM
The charging system is an integral part of the bat-
tery and starting systems. Because all these systems
work in conjunction, diagnose and test them together.
Circuit A11 connects to the generator output termi-
nal and splices to fuse 1 and fuse 8 in the Power Dis-
tribution Center (PDC). Circuit A0 connects the
battery to the PDC.
Circuit Z0 provides ground for the generator. Cir-
cuit Z0 attaches to the right rear of the engine.
When the ignition switch is in either the START or
RUN positions, it connects circuit A1 from fuse 6 in
the PDC to circuit A21. Circuit A21 splices to supply
current to the coil side of the automatic shut down
(ASD) relay. The powertrain control module (PCM)
provides ground for the relay on circuit K51. Circuit
K51 connects to cavity 51 of the PCM.
When the PCM grounds the ASD relay, contacts in-
side the relay close and connect circuit A18 from fuse
14 in the PDC to circuit A142. Circuit A142 splices to
the generator field terminal.
The PCM has an internal voltage regulator that
controls generator output. The PCM controls the gen-
erator field on circuit K20. Circuit K20 connects to
PCM cavity 20.
When the engine operates and there is current in
the generator field, the generator produces a B+ volt-
age. The generator supplies B+ voltage to the battery
through the A11 and A0 circuits.
HELPFUL INFORMATION
²If the vehicle is equipped with a 2.5L engine, cir-
cuit Z0 also connects to the battery.
²Circuit A14 from fuse 2 in the PDC supplies volt-
age to the fuse block for fuse 14.
²The ignition switch also connects circuit A1 with
circuits A41, A38, and A48.
²Circuit A21 also splices to power fuse 17 in the
fuse block.
²Circuit A21 also powers the coil side of the fuel
pump relay.
²The ASD relay supplies battery voltage for the fuel
injectors, ignition coil, and the heated oxygen sensor.
The fuel pump relay powers the fuel pump module.
²Circuit K51 also provides ground for the coil side
of the fuel pump relay.
DIAGRAM INDEX
Component Page
Battery (2.5L)...........................8W-20-2
Battery (4.0L)...........................8W-20-3
PDC Fuse 1 (2.5L).......................8W-20-2
PDC Fuse 1 (4.0L).......................8W-20-3
PDC Fuse 9 (2.5L).......................8W-20-2
PDC Fuse 9 (4.0L).......................8W-20-3
Generator (2.5L).........................8W-20-2
Generator (4.0L).........................8W-20-3
Powertrain Control Module (2.5L)..............8W-20-2
Powertrain Control Module (4.0L)..............8W-20-3
J8W-20 CHARGING SYSTEMÐXJ VEHICLES 8W - 20 - 1

STARTING SYSTEM
INDEX
page page
Diagram Index............................ 1Starting System........................... 1
STARTING SYSTEM
AUTOMATIC TRANSMISSIONS
Circuit A0 from the battery is double crimped at
the positive battery post. One branch of circuit A0
(battery positive cable) connects to the engine starter
motor. The other A0 branch supplies voltage to the
bus bar in the power distribution center (PDC).
Fuse 7 in the PDC supplies battery voltage to the
contact side of the engine starter motor relay on cir-
cuit A4. When the coil side of the engine starter mo-
tor relay energizes, the contacts close and connect
circuit A4 to circuit T40. Circuit T40 supplies battery
voltage to the starter motor solenoid.
The ignition switch supplies battery voltage to the
coil side of the starter motor relay on circuit A41
when the key is moved to the START position and
the PARK/NEUTRAL position switch is closed.
Ground for the coil side of the starter motor relay is
supplied by the case grounded PARK/NEUTRAL po-
sition switch. Circuit T41 connects the coil side of the
relay to the PARK/NEUTRAL position switch.
When the starter motor relay energizes and the
contacts close, circuit T40 supplies battery voltage to
the starter motor solenoid. Circuit A0 from the bat-
tery supplies voltage to the starter motor when the
solenoid energizes.
MANUAL TRANSMISSIONS
Circuit A0 from the battery is double crimped at
the positive battery post. One branch of circuit A0
(battery positive cable) connects to the battery
starter motor. The other A0 branch supplies voltage
to the buss bar in the power distribution center
(PDC).
Fuse 7 in the PDC supplies battery voltage to the
contact side of the engine starter motor relay on cir-
cuit A4. When the coil side of the engine starter mo-
tor relay energizes, the contacts close and connect
circuit A4 to circuit T40. Circuit T40 supplies battery
voltage to the starter motor solenoid.The ignition switch supplies battery voltage to the
coil side of the starter motor relay on circuit A41
when the key is moved to the START position. Cir-
cuit Z12 provides ground for the coil side of the relay.
When the starter motor relay energizes and the
contacts close, circuit T40 supplies battery voltage to
the starter motor solenoid. Circuit A0 from the bat-
tery supplies voltage to the starter motor when the
solenoid energizes.
HELPFUL INFORMATION
²The Park/Neutral switch closes when the trans-
mission is in either the PARK or NEUTRAL posi-
tions.
²Circuit T41 also connects to cavity 30 of the pow-
ertrain control module (PCM). This input tells the
PCM the operator is starting the vehicle.
²Circuit A4 is double crimped at the contact side of
the starter motor relay. The A4 branch leaving the
relay powers fuse 13 in the PDC.
DIAGRAM INDEX
Component Page
Battery (2.5L)...........................8W-21-2
Battery (4.0L)...........................8W-21-3
Engine Starter Motor (2.5L)..................8W-21-2
Engine Starter Motor (4.0L)..................8W-21-3
Engine Starter Motor Relay (2.5L)..............8W-21-2
Engine Starter Motor Relay (4.0L)..............8W-21-3
Ignition Switch (2.5L)......................8W-21-2
Ignition Switch (4.0L)......................8W-21-3
PDC Fuse 6 (2.5L).......................8W-21-2
PDC Fuse 6 (4.0L).......................8W-21-3
PDC Fuse 7 (2.5L).......................8W-21-2
PDC Fuse 7 (4.0L).......................8W-21-3
Powertrain Control Module (2.5L)..............8W-21-2
Powertrain Control Module (4.0L)..............8W-21-3
Park/Neutral Position Switch (2.5L).............8W-21-2
Park/Neutral Position Switch (4.0L).............8W-21-3
J8W-21 STARTING SYSTEMÐXJ VEHICLES 8W - 21 - 1

FUEL/IGNITION
INDEX
page page
Automatic Shut Down (ASD) Relay............. 1
Battery Feed.............................. 1
Brake Switch Input......................... 5
Camshaft Position Sensor.................... 3
CCDBus ................................ 5
Crankshaft Position Sensor................... 3
Data Link Connector........................ 5
Diagram Index Ð2.5L Engine.................. 6
Diagram Index Ð4.0L Engine.................. 6
Engine Coolant Temperature Sensor............ 3
Extended Idle Switch....................... 5
Fuel Injectors............................. 1
Fuel Pump Module......................... 2
Fuel Pump Relay.......................... 2
Heated Oxygen Sensor...................... 3Idle Air Control (IAC) Motor................... 2
Ignition Coil.............................. 2
Ignition Switch............................ 1
Intake Air Temperature Sensor................ 4
Malfunction Indicator Lamp (MIL)............... 5
Manifold Absolute Pressure Sensor............. 4
Park/Neutral Position Switch.................. 4
Power (Device) Ground...................... 5
Power Steering Pressure Switch............... 5
Tachometer Signal......................... 5
Throttle Position Sensor..................... 4
Torque Converter Clutch (TCC) Solenoid and
Relay................................. 4
Upshift Lamp............................. 5
Vehicle Speed Sensor....................... 2
IGNITION SWITCH
Circuit A1 from fuse 11 in the power distribution
center (PDC), supplies battery voltage to the ignition
switch. Depending upon position, the ignition switch
powers circuits A21, A38, A41, or A48.
START POSITION
In the START position, the ignition switch connects
circuit A1 to circuit A41. Circuit A41 connects to the
coil side of the starter motor relay.
Additionally in the START position, the case
grounded ignition switch provides ground for the
brake lamp switch and the warning lamps in the
instrument cluster.
START OR RUN POSITION
In the START or RUN position, the ignition switch
connects circuit A1 to circuit A21. Circuit A21 splices
to power fuse 17 in the fuse block and the coil side of
the Automatic Shut Down (ASD) relay and the fuel
pump relay.
RUN (ONLY) POSITION
When the ignition switch is in the RUN position, it
connects circuit A1 to circuit A38. Circuit A22 splices
to power fuses 1 and 7 in the fuse block.
²Fuse 1 powers the rear wiper system on circuit
V15.
²Fuse 7 feeds the Anti-Lock Brake System (ABS) on
circuit 236.
ACCESSORY OR RUN POSITIONS
In the ACCESSORY or RUN positions, the ignition
switch connects circuit A1 to circuit A48. Circuit A48
connects to a bus bar in the fuse block that feeds
fuses 2, 5, and 8.
AUTOMATIC SHUT DOWN (ASD) RELAY
When the ignition switch is in either the START or
RUN positions, it connects circuit A1 from fuse 6 in
the Power Distribution Center (PDC) to circuit A21.
Circuit A21 supplies battery voltage to the coil side of
the Automatic Shut Down (ASD) relay. The Power-
train Control Module (PCM) provides ground for the
relay on circuit K51. Circuit K51 connects to cavity 51
of the PCM.
When the PCM grounds the ASD relay, contacts
inside the relay close and connect circuit A18 from
fuse 14 in the PDC to circuit A142. Circuit A142
splices to the generator field terminal, fuel injectors,
and ignition coil. Circuit A142 also connects to cavity
57 of the PCM.
HELPFUL INFORMATION
²Along with supplying voltage to the coil side of the
ASD relay, circuit A21 also supplies voltage to the coil
side of the fuel pump relay.
BATTERY FEED
Circuit A14 from fuse 2 in the Power Distribution
Center (PDC) supplies battery voltage to cavity 3 of
the powertrain control module.
HELPFUL INFORMATION
Circuit A14 also supplies power to the contact sides
of the fuel pump relay and fuse F2 in the PDC. Fuse
F2 powers circuit A18 which supplies voltage to the
contact side of the automatic shut down relay.
FUEL INJECTORS
When the Automatic Shut Down (ASD) relay con-
tacts close, they connect circuits A14 and A142. Cir-
J8W-30 FUEL/IGNITIONÐXJ VEHICLES 8W - 30 - 1

cuit A142 supplies voltage to the fuel injectors. Each
injector has a separate ground circuit controlled by
the PCM.
Circuit K11 provides ground for injector number
one. The K11 circuit connects to cavity 16 of the
PCM.
Circuit K12 provides ground for injector number
two. The K12 circuit connects to cavity 15 of the
PCM.
Circuit K13 provides ground for injector number
three. The K13 circuit connects to cavity 14 of the
PCM.
Circuit K14 provides ground for injector number
four. The K14 circuit connects to cavity 13 of the
PCM.
On the 4.0L engine, circuit K15 provides ground for
injector number five. The K15 circuit connects to cav-
ity 38 of the PCM.
Also on the 4.0L engine, circuit K16 provides
ground for injector number six. The K16 circuit con-
nects to cavity 58 of the PCM.
HELPFUL INFORMATION
²Circuit A142 splices to supply voltage to the fuel
injectors, ignition coil, PCM, generator.
²For information about fuel injector operation, refer
to Group 14.
IGNITION COIL
When the Automatic Shut Down (ASD) relay con-
tacts close, they connect circuits A14 and A142. Cir-
cuit A142 supplies voltage to the fuel injectors.
Circuit A142 splices to supply voltage to the ignition
coil. The PCM controls the ground path for the igni-
tion coil on circuit K19. Circuit K19 connects to cav-
ity 19 of the PCM.
HELPFUL INFORMATION
Circuit A142 splices to supply voltage to the fuel
injectors, ignition coil, PCM, and generator.
FUEL PUMP RELAY
When the ignition switch is in either the START or
RUN positions, it connects circuit A1 from fuse 6 in
the Power Distribution Center (PDC) to circuit A21.
Circuit A21 supplies battery voltage to the coil side of
the fuel pump relay. The Powertrain Control Module
(PCM) provides ground for the relay on circuit K51.
Circuit K51 connects to cavity 51 of the PCM.
When the PCM grounds the fuel pump relay, con-
tacts inside the relay close and connect circuit A14
from fuse 2 in the PDC to circuit A141. Circuit A141
supplies voltage to the fuel pump motor (part of the
in-tank fuel pump module).
HELPFUL INFORMATION
²Circuit A14 also splices to supply battery voltage
to cavity 3 of the PCM.²Circuit A141 also supplies battery voltage to the
heated oxygen sensor.
FUEL PUMP MODULE
FUEL PUMP MOTOR
When the fuel pump relay contacts close, the relay
supplies voltage to the fuel pump motor. Circuit A141
from the relay supplies voltage to circuit A241. Cir-
cuit A241 connects to circuit F9 in the fuel pump
module harness. Circuit F9 connects to the fuel pump
motor.
Circuit 99 in the fuel pump module harness con-
nects to circuit Z1. Circuit Z1 provides ground for the
fuel pump motor.
FUEL LEVEL SENSOR
The fuel level sensor is a variable resistor. Circuit
G4 connects the fuel level sensor to the fuel gauge in
the instrument cluster. Circuit F87 from fuse 17 in
the fuse block supplies voltage to the fuel gauge. The
fuel level sensor draws voltage from circuit F87
through the fuel gauge on circuit G4. Circuit G4 con-
nects to circuit 57 in the fuel pump module harness.
Circuit 57 connects to the fuel level sensor.
Circuit 99 in the fuel pump module harness con-
nects to circuit Z1. Circuit Z1 provides the ground
path for the fuel level sensor. The grounding point for
circuit Z1 is the left side of the cowl panel.
HELPFUL INFORMATION
As current flows through the coils in the fuel
gauge, it creates a magnetic field. One of the coils in
the gauge receives fixed current. The other coil is
connected to the level sensor. The magnetic field con-
trols the position of the fuel gauge pointer.
The fuel level sensor contains a variable resistor.
As the position of the float arm on the fuel level sen-
sor changes, the resistor changes the current flow
through second coil in the fuel gauge. A change in
current flow alters the magnetic field in the fuel
gauge, which changes the pointer position.
IDLE AIR CONTROL (IAC) MOTOR
The Powertrain Control Module (PCM) operates
the idle air control motor through 4 circuits - K39,
K40, K59, and K60. Each circuit connects to separate
cavities in the PCM connector.
²Circuit K39 connects to cavity 39 of the PCM
²Circuit K40 connects to cavity 40 of the PCM
²Circuit K59 connects to cavity 59 of the PCM
²Circuit K60 connects to cavity 60 of the PCM
VEHICLE SPEED SENSOR
Circuit K7 supplies 8 volts from the Powertrain
Control Module (PCM) to the vehicle speed sensor.
The K7 circuit connects to cavity 7 of the PCM.
8W - 30 - 2 8W-30 FUEL/IGNITIONÐXJ VEHICLESJ