relay JEEP YJ 1995 Service And Workshop Manual

DIAGRAM INDEXÐ2.5L ENGINE
Component Page
Automatic Shut Down Relay.................8W-30-8
Camshaft Position Sensor..................8W-30-10
Crankshaft Position Sensor.................8W-30-11
Data Link Connector......................8W-30-12
Distributor Ignition Coil....................8W-30-12
Engine Coolant Temperature Sensor............8W-30-11
Fuel Injector #1.........................8W-30-9
Fuel Injector #2.........................8W-30-9
Fuel Injector #3.........................8W-30-9
Fuel Injector #4.........................8W-30-9
Fuel Pump Relay........................8W-30-20
Fuel Tank Gauge Level Sending Unit...........8W-30-20
Fuse 2 (PDC)........................8W-30-8, 20
Fuse 6 (PDC)........................8W-30-8, 20
Fuse 11 (PDC).........................8W-30-12
Fuse 14 (PDC)..........................8W-30-8
Heated Oxygen Sensor.....................8W-30-7
Idle Air Control Motor.....................8W-30-7
Ignition Switch.......................8W-30-8, 20
Instrument Cluster....................8W-30-12, 20
Intake Air Temperature Sensor...............8W-30-11
MAP Sensor...........................8W-30-10
Powertrain Control Module........8W-30-7 thru 12, 19, 20
Power Steering Pressure Switch...............8W-30-7
Throttle Position Sensor...................8W-30-10
Vehicle Speed Sensor.....................8W-30-12
DIAGRAM INDEXÐ4.0L ENGINE
Component Page
Automatic Shut Down Relay.................8W-30-14
Camshaft Position Sensor..................8W-30-16
Crankshaft Position Sensor.................8W-30-16
Data Link Connector......................8W-30-18
Distributor Ignition Coil....................8W-30-18
Engine Coolant Temperature Sensor............8W-30-17
Extended Idle Switch.....................8W-30-19
Extended Idle Switch Lamp.................8W-30-19
Fuel Injector #1.........................8W-30-15
Fuel Injector #2.........................8W-30-15
Fuel Injector #3.........................8W-30-15
Fuel Injector #4.........................8W-30-15
Fuel Injector #5.........................8W-30-15
Fuel Injector #6.........................8W-30-15
Fuel Pump Relay........................8W-30-20
Fuel Tank Gauge Level Sending Unit...........8W-30-20
Fuse 2 (PDC).......................8W-30-14, 20
Fuse 3 (Fuse Block)......................8W-30-19
Fuse 5 (PDC)..........................8W-30-19
Fuse 6 (PDC).....................8W-30-14, 19, 20
Fuse 14 (PDC).........................8W-30-14
Fuse 15 (Fuse Block).....................8W-30-19
Fuse 19 (Fuse Block).....................8W-30-19
Headlamp Switch........................8W-30-19
Heated Oxygen Sensor....................8W-30-13
Idle Air Control Motor.....................8W-30-13
Ignition Switch....................8W-30-14, 19, 20
Instrument Cluster.......................8W-30-18
Intake Air Temperature Sensor...............8W-30-17
MAP Sensor...........................8W-30-16
Powertrain Control Module............8W-30-13 thru 20
Throttle Position Sensor...................8W-30-16
Vehicle Speed Sensor.....................8W-30-18
8W - 30 - 6 8W-30 FUEL/IGNITIONÐXJ VEHICLESJ

TRANSMISSION CONTROLS
UPSHIFT LAMP
On vehicles equipped with a manual transmission,
the PCM grounds the up-shift lamp on circuit K54.
Circuit K54 connects to cavity 54 of the PCM.
FOUR-WHEEL DRIVE (4WD) SWITCH
When the 4WD switch closes, circuit Z1 provides
ground for the 4WD indicator lamp in the instrument
cluster. Circuit F87 connects to the instrument clus-
ter and supplies battery voltage to the 4WD indicator
lamp. Circuit 107 connects the indicator lamp to the
4WD switch. Circuit 106 connects the lamp to the in-
strument cluster and circuit F87.
TRANSMISSION CONTROL MODULEÐ4.0L
ENGINE ONLY
Vehicles equipped with the 4.0L engine have elec-
tronically controlled solenoids in the automatic trans-
mission valve body.
The Transmission Control Module (TCM) receives
inputs from the Throttle Position Sensor (TPS) on
circuit K22 and the stop lamp switch on circuit K29.
Circuit K4 connects to the TCM to provide ground for
the TPS signal. The TCM receives the transmission
output speed sensor signal on circuit T505. Circuit
A14 from fuse 2 in the Power Distribution Center
supplies battery voltage to the TCM. Circuit Z12 pro-
vides ground for the TCM.
The TCM powers the S1 solenoid on circuit T510,
the S2 solenoid on circuit T509, and the S3 solenoid
on circuit T508. Circuit Z12 provides ground for the
S1, S2, and S3 solenoids.
TORQUE CONVERTER CLUTCH (TCC) SOLENOID
AND RELAYÐ2.5L ENGINE ONLY
The TCC solenoid is only used on 2.5L engines
with the three-speed automatic transmissions. The
Powertrain Control Module (PCM) operates the TCC
solenoid by energizing the TCC relay.
Circuit T17 from fuse 12 in the Power Distribution
Center (PDC) supplies voltage to the coil and contact
sides of the TCC relay. When the PCM provides a
ground path on circuit K54 for the coil side of the re-
lay, the relay contacts close.
When the relay contacts close, they connect circuit
T17 with circuit T22. Circuit T22 supplies battery
voltage to the case grounded TCC solenoid. Circuit
K54 connects to PCM cavity 54.
HELPFUL INFORMATION
²In the RUN or START position, the ignition switch
connects circuit A1 from fuse 6 in the PDC to circuit
A21.
DIAGRAM INDEX
Component Page
4-WD Indicator Lamp......................8W-31-4
4-WD Indicator Switch.....................8W-31-4
Back-Up Lamp Switch.....................8W-31-3
Fuse 2 (PDC)...........................8W-31-4
Fuse 6 (PDC).........................8W-31-2, 3
Fuse 11 (PDC)..........................8W-31-3
Fuse 12 (PDC)..........................8W-31-2
Ignition Switch........................8W-31-2, 3
Powertrain Control Module..................8W-31-2
Park/Neutral Position Switch.................8W-31-3
TCC Relay.............................8W-31-2
TCC Solenoid...........................8W-31-2
Transmission Control Module.................8W-31-2
J8W-31 TRANSMISSION CONTROLSÐXJ VEHICLES 8W - 31 - 1

ANTI-LOCK BRAKES
INDEX
page page
ABS Power Relay.......................... 1
ABS Pump Motor Relay..................... 1
ABS Warning Lamp........................ 2
Acceleration Switch......................... 1
Brake Switch Input......................... 2
Data Link Connector........................ 2Diagram Index............................ 3
General Information........................ 1
Hydraulic Control Unit....................... 2
Pump Motor Speed Sensor................... 2
Wheel Speed Sensors...................... 1
GENERAL INFORMATION
Three fuses supply power for the Anti-Lock Brake
System (ABS); fuses 8 and 10 in the Power Distribu-
tion Center (PDC) and fuse 7 in the fuse block. Fuses
8 and 10 in the PDC are connected directly to battery
voltage and are HOT all times. Fuse 7 in the fuse
block is HOT when the ignition switch is the RUN
Position.
In the RUN position, the ignition switch connects
circuit A1 from fuse 6 in the PDC with circuit A38.
Circuit A38 connects to a bus bar in the fuse block.
The bus bar feeds circuit B236 through fuse 7. Fuse 7
is a 2 amp fuse.
Circuit B236 connects to the coil side of the ABS
power relay and cavity 53 of the ABS control module.
Circuit Z1 provides ground for the ABS control mod-
ule. Circuit Z1 connects to cavities 1 and 19 of the
ABS control module.
Refer to group 5, Brakes for operational descrip-
tions of ABS system components.
WHEEL SPEED SENSORS
The all wheel anti-lock system uses four wheel
speed sensors; one for each wheel. Each sensor con-
verts wheel speed into an electrical signal that it
transmits to the ABS control module. A pair of
twisted wires connect to each sensor to provide sig-
nals to the ABS control module.
Circuits B6 and B7 provide signals to ABS control
module from right front wheel speed sensor. Circuit
B6 which provides the LOW signal connects to cavity
29 of the ABS control module. Circuit B7 connects to
cavity 47 of the module and provides the HIGH sig-
nal.
Circuits B8 and B9 provide signals to ABS control
module from left front wheel speed sensor. Circuit B8,
which provides the LOW signal, connects to cavity 30
of the ABS control module. Circuit B9 connects to
cavity 48 of the module and provides the HIGH sig-
nal.
Circuits B1 and B2 provide signals to ABS control
module from right rear wheel speed sensor. Circuit
B1 which provides the LOW signal connects to cavity45 of the ABS control module. Circuit B2 connects to
cavity 27 of the module and provides the HIGH sig-
nal.
Circuits B4 and B3 provide signals to ABS control
module from left rear wheel speed sensor. Circuit B3,
which provides the LOW signal, connects to cavity 28
of the ABS control module. Circuit B4 connects to
cavity 46 of the module and provides the HIGH sig-
nal.
ACCELERATION SWITCH
During four-wheel drive operation, the acceleration
(G) switch provides deceleration data to the ABS con-
trol module. Refer to Group 5, Brakes for additional
information.
Circuits B515, B516, and B517 connect the accel-
eration sensor to the ABS control module. Circuits
B515 and B516 provide switch states while circuit
B517 provides ground. At the ABS control module
circuit B515 connects to cavity 25, circuit B516 con-
nects to cavity 43 and circuit B517 connects to cavity
26.
ABS POWER RELAY
The ABS power relay is located in the power distri-
bution center (PDC). When the ABS module grounds
the ABS power relay on circuit B207, the relay
switches to connect circuit A20 from PDC fuse 10 to
circuit B235. Circuit B236 from fuse 7 in the fuse
block splices to feed the coil side of the ABS power
relay. Circuit B207 connects to cavity 34 of the ABS
control module.
Circuit B235 is double crimped at the ABS power
relay. One branch of circuit B235 supplies power to
the coil side of the ABS pump motor relay. The other
branch of circuit B235 splices to cavities 3 and 33 of
the ABS control module and to the hydraulic control
unit.
ABS PUMP MOTOR RELAY
The ABS pump motor relay in the power distribu-
tion center (PDC) supplies voltage to the ABS pump
motor. When the ABS power relay energizes, circuit
B235 supplies battery voltage to the coil side of the
J8W-32 ANTI-LOCK BRAKESÐXJ VEHICLES 8W - 32 - 1

ABS pump motor relay. The ABS control module pro-
vides ground for the relay on circuit B116. Circuit
B116 connects to cavity 15 of the ABS control mod-
ule.
When the ABS pump motor energizes, it connects
circuit A10 from PDC fuse 8 to circuit B233. Circuit
B233 supplies battery voltage to the pump motor.
Circuit Z12 provides ground for the pump motor.
PUMP MOTOR SPEED SENSOR
The input from the pump motor speed sensor tells
the ABS control module that the pump is operating.
Circuits B219 and B220 from the control module con-
nect to the speed sensor.
BRAKE SWITCH INPUT
Circuit L50 from the stop lamp provides the brake
switch input to the ABS control module. When the
brake pedal is depressed, the stop lamp switch closes
to supply battery voltage from circuit L9 to circuit
L50. Circuit L50 connects to cavity 32 of the ABS
control module. Circuit L9 originates at fuse 4 in the
Power Distribution Center (PDC).
HYDRAULIC CONTROL UNIT
When the ABS power relay energizes, two branches
of circuit B235 splice to supply voltage to the isola-
tion and dump solenoids in the hydraulic control
unit. The hydraulic control unit contains three sepa-
rate isolation solenoids and three separate dump so-
lenoids. The ABS control module activates the decay
and isolation solenoids by providing separate ground
paths for each.
The ABS module provides a ground path for the
rear isolation solenoid on circuit B251. Circuit B251
connects to cavity 54 of the ABS control module.
For the right front isolation solenoid, the ABS mod-
ule provides a ground path on circuit B249. Circuit
B249 connects to cavity 38 of the ABS control mod-
ule.
On circuit B245, the ABS module provides ground
for the left front isolation solenoid. Circuit B245 con-
nects to cavity 20 of the ABS control module.
The ABS module provides a ground path for the
rear decay solenoid on circuit B254. Circuit B254
connects to cavity 36 of the ABS control module.For the right front decay solenoid, the ABS module
provides a ground path on circuit B248. Circuit B248
connects to cavity 21 of the ABS control module.
On circuit B243, the ABS module provides ground
for the left decay solenoid. Circuit B243 connects to
cavity 2 of the ABS control module.
ABS WARNING LAMP
Circuit F87 provides power for the ABS warning
lamp at the instrument cluster. Ground for the ABS
warning lamp is provided by either the ABS control
module or by the ABS power relay when the relay is
not energized. The ABS control module illuminates
the lamp by providing ground on circuit B205.
Circuit B205 splices to connect to circuit B235
through a diode. When the ABS power relay is not
energized, it connects circuit B235 to circuit Z12. The
ground path for the warning lamp is through the di-
ode to circuit B235, through the ABS power relay to
ground on circuit Z12.
The diode between circuit B205 and B235 prevents
voltage from flowing to the ABS control module when
the ABS power relay switches to supply power on cir-
cuit B235.
DATA LINK CONNECTOR
Circuit D1 from cavity 23 of the ABS control mod-
ule receives data from the DRB scan tool through the
data link connector. The ABS control module trans-
mits data to the scan tool through the connector on
circuit D2. Circuit D2 originates at cavity 42 of the
ABS control module.
Through the data link connector, circuit Z12 pro-
vides ground for the DRB scan tool.
Circuit A4 from fuse 10 in the Power Distribution
Center (PDC) supplies power to fuse 5 in the PDC.
Fuse 5 powers circuit F39 which supplies battery
voltage to the scan tool through the diagnostic con-
nector.
HELPFUL INFORMATION
²Check fuses 10 and 5 in the PDC.
²If the vehicle is equipped with an automatic trans-
mission, circuits D1 and D2 are double crimped at
the data link connector and connect to the Power-
train Control Module (PCM).
8W - 32 - 2 8W-32 ANTI-LOCK BRAKESÐXJ VEHICLESJ

DIAGRAM INDEX
Component Page
ABS Control Module..................8W-32-4 thru 8
ABS Hydraulic Unit.......................8W-32-6
ABS Power Relay........................8W-32-4
ABS Pump Motor........................8W-32-5
ABS Pump Motor Relay....................8W-32-4
Data Link Connector......................8W-32-8
Diode................................8W-32-6
Fuse 6 (PDC)...........................8W-32-5
Fuse 7 (Fuse Block).......................8W-32-5
Fuse 7 (PDC)...........................8W-32-8
Fuse 8 (PDC)...........................8W-32-5
Fuse 10 (PDC)..........................8W-32-4
Fuse 13 (PDC)..........................8W-32-8
G-Sensor..............................8W-32-8
Ignition Switch..........................8W-32-5
Powertrain Control Module..................8W-32-8
Telltale Connector (Instrument Cluster)...........8W-32-6
Transmission Control Module.................8W-32-8
Wheel Speed Sensors......................8W-32-7
J8W-32 ANTI-LOCK BRAKESÐXJ VEHICLES 8W - 32 - 3

VEHICLE SPEED CONTROL
VEHICLE SPEED CONTROL
The vehicle speed control system is operated by the
Powertrain Control Module (PCM). Circuit F12 from
fuse 11 in the Power Distribution Center (PDC) sup-
plies battery voltage to the vehicle speed control ON/
OFF switch. Circuit A21 supplies voltage to fuse 11
when the ignition switch is in the START or RUN po-
sitions. In the START or RUN position the ignition
switch connects circuit A21 with circuit A1. Fuse 6 in
the PDC protects circuit A1.
The vehicle speed control ON/OFF switch supplies
voltage to the SET/COAST and RESUME/ACCEL
switches. Both switches send signals to the PCM
(which supplies the ground path for the switches).
The PCM controls the vent and vacuum functions
of the speed control servo on circuits V35 and V36.
Depending on the signal it receives from the vehicle
speed control switches, the PCM either applies vac-
uum to, or vents vacuum from, the servo. Circuit V36
from cavity 33 of the PCM sends the vacuum signal
to the servo. Circuit V35 from cavity 53 sends the
vent signal.
Circuit V32 signals to the PCM that the speed con-
trol switch is in the ON position. The V32 circuit con-
nects to cavity 49 of the PCM. Circuit V32 also
connects to the stop lamp switch.
In the CLOSED position, the stop lamp switch con-
nects circuit V32 with circuit V30 to power the speed
control servo. Circuit Z1 provides ground for the
speed control servo.
Circuit V31 provides the SET/COAST signal to cav-
ity 48 of the PCM. Circuit V33 sends the RESUME/
ACCEL signal to cavity 50 of the PCM.
Circuit K29 connects to cavity 29 of the PCM and
to ground through the stop lamp switch. The stop
lamp switch OPENS when the operator depresses the
brake pedal. The PCM disables speed control when
the stop lamp switch opens. From the stop lamp
switch, circuit Z1 provides ground for circuit K29.
HELPFUL INFORMATION
²Circuit K29 also connects to the ABS control mod-
ule on vehicles with all wheel anti-lock brakes.
²On vehicles with the 4.0L Engine and Automatic
Transmission, Circuit K29 connects to the Transmis-
sion Control Module (TCM).
DIAGRAM INDEX
Component Page
ABS Control Module..................8W-32-4 thru 8
ABS Hydraulic Unit.......................8W-32-6
ABS Power Relay........................8W-32-4
ABS Pump Motor........................8W-32-5
ABS Pump Motor Relay....................8W-32-4
Data Link Connector......................8W-32-8
Diode................................8W-32-6
Fuse 6 (PDC)...........................8W-32-5
Fuse 7 (Fuse Block).......................8W-32-5
Fuse 7 (PDC)...........................8W-32-8
Fuse 8 (PDC)...........................8W-32-5
Fuse 10 (PDC)..........................8W-32-4
Fuse 13 (PDC)..........................8W-32-8
G-Sensor..............................8W-32-8
Ignition Switch..........................8W-32-5
Powertrain Control Module..................8W-32-8
Telltale Connector (Instrument Cluster)...........8W-32-6
Transmission Control Module.................8W-32-8
Wheel Speed Sensors......................8W-32-7
J8W-33 VEHICLE SPEED CONTROLÐXJ VEHICLES 8W - 33 - 1

OIL PRESSURE GAUGE
The case grounded oil pressure sensor is a variable
resistor that connects to circuit G6. Circuit G6 con-
nects to the oil pressure gauge.
Circuit F87 connects to the instrument cluster con-
nector and supplies battery voltage to oil pressure
gauge. The gauge uses two coils. Current passing
through the coils creates a magnetic field. Position of
the gauge needle is controlled by the amount of cur-
rent passing through the coils to ground at the sen-
sor.
OIL PRESSURE WARNING LAMP
The case grounded oil pressure switch connects to
circuit G6. Circuit G6 connects to the oil pressure
warning lamp. Circuit F87 connects to the instru-
ment cluster connector and supplies battery voltage
to oil pressure lamp.
When the oil pressure switch close, battery voltage
flows through the warning lamp to ground through
the switch, illuminating the lamp.
TACHOMETER
The tachometer module in the instrument cluster
operates the tachometer. The Powertrain Control
Module (PCM) supplies the signal for the tachometer
on circuit G21. Circuit G21 connects to cavity 43 of
the PCM.
SPEEDOMETER
The speedometer and odometer receive a signal
from the vehicle speed sensor on circuit G7. Circuit
G7 also connects to the Powertrain Control Module
(PCM) at cavity 47.
ABS WARNING LAMP
Circuit F87 provides power for the ABS warning
lamp at the instrument cluster. Ground for the ABS
warning lamp is provided by either the ABS control
module or by the ABS power relay when the relay is
not energized. The ABS control module illuminates
the lamp by providing ground on circuit B205.
Circuit B205 splices to connect to circuit B235
through a diode. When the ABS power relay is not
energized, it connects circuit B235 to circuit Z12. The
ground path for the warning lamp is through the di-
ode to circuit B235, through the ABS power relay to
ground on circuit Z12.
The diode between circuit B205 and B235 prevents
voltage from flowing to the ABS control module when
the ABS power relay switches to supply power on cir-
cuit B235.
MALFUNCTION INDICATOR LAMP (MIL)
The PCM provides ground for the instrument clus-
ter malfunction indicator lamp on circuit G3. Circuit
G3 connects to cavity 32 of the PCM. Circuit F87provides voltage for the lamp. The MIL displays the
message CHECK ENGINE when illuminated.
For information regarding diagnostic trouble code
access using the MIL lamp, refer to Group 14, Fuel
Systems.
LOW WASHER FLUID WARNING LAMP
Circuit G29 connects the low washer fluid switch to
the warning lamp in the instrument cluster. Circuit
F12 supplies battery voltage to the switch.
When the low washer fluid switch closes, it con-
nects circuits G29 and F12. Battery voltage from cir-
cuit F12 powers the low washer fluid lamp. Circuit
Z1 at the instrument cluster provides ground to illu-
minate the warning lamp.
SEAT BELT INDICATOR WARNING LAMP
The seat belt indicator warning lamp is activated
by the chime/buzzer on circuit G11. Circuit G11 sup-
plies power to instrument cluster for the lamp. Cir-
cuit Z1 provides ground for the lamp at the cluster.
The chime/buzzer module powers circuit G11 after
it receives an input on circuit G10 indicating the seat
belt switch is open.
HIGH-BEAM INDICATOR LAMP
Circuit L3 supplies power for the high-beam indi-
cator lamp. The ground path for the lamp is through
circuit Z1. If the vehicle has Daytime Running
Lamps (DRL), the DRL module powers circuit L3
through circuit G465. On vehicles not equipped with
DRL, the headlamp switch powers circuit L3.
Circuit Z1 provides ground for the indicator lamp
at the cluster.
TURN SIGNAL INDICATOR LAMPS
Circuits L61 and L60 power for the turn signal in-
dicator lamps. Circuit L61 powers the left indicator
lamp. Circuit L60 powers the right indicator lamp.
Circuit Z1 provides ground for the lamps.
BRAKE WARNING LAMP
Circuit F87 supplies power to the park brake lamp.
Ground for the park brake lamp is supplied through
the case grounded park brake switch or brake warn-
ing switch on circuit G9. Circuit G9 Connects to cir-
cuit B203. Circuit B203 connects to the brake
warning lamp at the instrument cluster.
MANUAL TRANSMISSION UP-SHIFT LAMP
Circuit F87 supplies power for the manual trans-
mission up-shift lamp. The lamp illuminates when
the Powertrain Control Module (PCM) provides
ground for the lamp on circuit K54. Circuit K54 con-
nects to cavity 54 of the PCM.
8W - 40 - 2 8W-40 INSTRUMENT CLUSTERÐXJ VEHICLESJ

HORN/CIGAR LIGHTER
HORN
The horn system uses two switches and horn relay.
The horn switches are on the steering wheel.
Circuit A7 from fuse 3 in the Power Distribution
Center (PDC) feeds a fuse block bus bar that powers
circuit X4 through fuse 11. Circuit X4 is HOT at all
times and powers the coil and contact sides of the
horn relay.
When the case grounded horn switch is depressed,
circuit X3 provides ground for the coil side of the re-
lay and the contacts close. When the contacts close,
circuit X2 supplies voltage to the case grounded
horns.
HELPFUL INFORMATION
²The horn switches are grounded to the steering
wheel.
²Circuit X4 is double crimped at the coil side of the
horn relay.
²Check fuse 3 in the PDC and fuse 11 in the fuse
block.
CIGAR LIGHTER
In the ACCESSORY or RUN position, the ignition
switch supplies voltage to fuse 2 in the fuse block on
circuit A48. Fuse 2 feeds circuit F85 which connects
to the cigar lighter. When the lighter is depressed,
the contacts inside of the lighter element close and
voltage flows to ground on circuit Z1.
HELPFUL INFORMATION
²In the ACCESSORY or RUN position, the ignition
switch connects circuit A1 from fuse 6 in the PDC
with circuit A48.
²Circuit F85 also powers the radio and LCD relay.
DIAGRAM INDEX
Component Page
Cigar Lighter...........................8W-41-3
Fuse 3 (PDC)...........................8W-41-2
Fuse 6 (PDC)...........................8W-41-3
Fuse 11 (Fuse Block)......................8W-41-2
Fuse 2 (Fuse Block).......................8W-41-3
Horns................................8W-41-2
Horn Relay.............................8W-41-2
Horn Switch............................8W-41-2
Ignition Switch..........................8W-41-3
J8W-41 HORN/CIGAR LIGHTERÐXJ VEHICLES 8W - 41 - 1

AIR CONDITIONING/HEATER
CONTENTS
page page
A/C-HEATER SYSTEM...................... 1 HEATERSYSTEM......................... 1
GENERAL INFORMATION
This section of the wiring diagrams is divided into
two sub-sections; Heater, and A/C and Heater. When
referring to the circuit descriptions or wiring dia-
grams, ensure that you use the correct sub-section.
HEATER SYSTEM
BLOWER MOTOR
In the RUN or ACCESSORY position, the ignition
switch connects circuit A1 from fuse 6 in the Power
Distribution Center (PDC) to circuit A48. Circuit A48
supplies battery voltage to fuse 5 in the fuse block.
Fuse 5 supplies power to the heat mode switch on
circuit C7.
Circuit C43 from the heat mode switch splices to
supply voltage to the blower motor switch and the
blower motor resistor block. The blower motor switch
sets blower motor speed to HIGH, M1, M2, or LOW.
When the blower motor switch is in the LOW posi-
tion, circuit C43 from the heat mode supplies voltage
to the resistor block. Voltage does not pass through
the blower motor switch in the LOW position.In the M1 position, the blower motor switch sup-
plies voltage to the resistor block on circuit C4. From
circuit C4, voltage passes through three resistors in
the resistor block to the blower motor on circuit C1.
In the M2 position, the blower motor supplies volt-
age to the resistor block on circuit C6. From circuit
C6 voltage flows through two resistors to the blower
motor on circuit C1.
In the HIGH position, the blower motor switch con-
nects directly to the blower motor on circuit C1. Volt-
age does not pass through the resistor block.
Circuit Z1 provides ground for the blower motor.
A/C-HEATER SYSTEM
GENERAL INFORMATION
Several fuses supply power for the air conditioning/
heater system. In the START or RUN positions, the
ignition switch connects circuit A1 from fuse 6 in the
Power Distribution Center (PDC) to circuit A21. Cir-
cuit A21 powers a bus bar in the PDC that feeds cir-
cuit F12 through fuse 11. Circuit F12 feeds the
contact side of the A/C compressor clutch relay and
the coil side of the radiator fan relay (4.0L engine).
In the RUN or ACCESSORY position, the ignition
switch connects circuit A1 from fuse 11 in the PDC to
circuit A48. Circuit A48 supplies battery voltage to
fuse 5 in the fuse block. Fuse 5 supplies power to the
A/C-Heater control switch on circuit C7.
Fuse 13 in the PDC supplies battery voltage to the
contact side of the radiator fan relay on circuit F141.
Circuit A14 from fuse 15 in the PDC powers PDC
fuse 4.
BLOWER MOTOR
In the RUN or ACCESSORY position, the ignition
switch connects circuit A1 from fuse 6 in the PDC to
circuit A48. Circuit A48 supplies battery voltage to
fuse 5 in the fuse block. Fuse 5 supplies power to the
A/C-Heater control switch on circuit C7.
Circuit C43 from the A/C-heater switch splices to
supply voltage to the blower motor switch and the
blower motor resistor block. The blower motor switch
sets blower motor speed to HIGH, M1, M2, or LOW.
When the blower motor switch is in the LOW posi-
tion, circuit C43 from the A/C-Heater switch supplies
voltage to the resistor block. Voltage does not pass
through the blower motor switch in the LOW position
In the M1 position, the blower motor switch sup-
plies voltage to the resistor block on circuit C4. From
circuit C4, voltage passes through three resistors in
the resistor block to the blower motor on circuit C1.
J8W-42 AIR CONDITIONING/HEATERÐXJ VEHICLES 8W - 42 - 1

In the M2 position, the blower motor supplies volt-
age to the resistor block on circuit C6. From circuit
C6 voltage flows through two resistors to the blower
motor on circuit C1.
In the HIGH position, the blower motor switch con-
nects directly to the blower motor on circuit C1. Volt-
age does not pass through the resistor block.
Circuit Z1 provides ground for the blower motor.
AIR CONDITIONING OPERATION
When the A/C-heater control switch is moved to an
A/C position or the defrost position, the Powertrain
Control Module (PCM) receives the A/C select signal
on circuit C90. Circuit C90 connects to cavity 28 of
the PCM.
Circuit also C90 splices to the low pressure switch
and to supply battery voltage to the coil side of the
A/C compressor clutch relay. If the low pressure
switch is closed, circuit C90 connects to circuit C21.
Circuit C21 supplies battery voltage to the A/C cy-
cling switch. Circuit C91 from the A/C cycling switch
provides the A/C request signal to the PCM. Circuit
C91 connects to cavity 27 of the PCM. Circuit Z1 pro-
vides ground for the A/C cycling switch.
After receiving the A/C request signal, the PCM
supplies ground for the A/C compressor clutch relay
on circuit C13. Circuit F12 from fuse 11 in the PDC
supplies battery voltage to the contact side of the A/C
compressor clutch relay. When the PCM grounds the
relay, the contacts close and connect circuit F12 to
circuit C3. Circuit C3 feeds the A/C compressor
clutch.
Also, after receiving the A/C request signal, the
PCM supplies ground for the coil side of the radiator
fan relay on circuit C27 (4.0L engine). Circuit C27
connects to cavity 31 of the PCM. Circuit F12 sup-
plies battery voltage to the coil side of the relay.
When the PCM grounds the coil side of the radia-
tor fan relay, the contacts close and connects circuit
F141 from fuse 4 in the PDC to circuit C25. Circuit
C25 feeds the radiator fan motor. Circuit Z1 provides
ground for the motor.
HELPFUL INFORMATION
Circuit A14 from PDC fuse 2 powers circuit F141
through fuse 15 in the PDC.
RADIATOR FAN RELAY AND MOTOR
In the START or RUN positions, the ignition
switch connects circuit A1 from fuse 6 in the Power
Distribution Center (PDC) to circuit A21. Circuit A21
powers a bus bar in the PDC that feeds circuit F12
through fuse 11. Circuit F12 feeds the coil side of the
radiator fan relay (4.0L engine).
The PCM supplies ground for the coil side of the
radiator fan relay on circuit C27 (4.0L engine). Cir-
cuit C27 connects to cavity 31 of the PCM.
When the PCM grounds the coil side of the radia-
tor fan relay, the contacts close and connects circuit
F141 from fuse 15 in the PDC to circuit C25. Circuit
C25 feeds the radiator fan motor. Circuit Z1 provides
ground for the radiator fan motor.
HELPFUL INFORMATION
Circuit A14 from PDC fuse 2 powers circuit F141
through fuse 15 in the PDC.
DIAGRAM INDEX
Component Page
A/C Compressor Clutch.....................8W-42-4
A/C Compressor Clutch Relay................8W-42-4
A/C Cycling Switch.......................8W-42-4
A/C Low Pressure Switch...................8W-42-4
A/C Mode Select Switch....................8W-42-5
Blower Motor...........................8W-42-3
Blower Motor Switch......................8W-42-3
Blower Motor Resistor.....................8W-42-3
Fuse 2 (PDC)...........................8W-42-5
Fuse 5 (Fuse Block).....................8W-42-3, 5
Fuse 6 (PDC).........................8W-42-3, 5
Fuse 11 (PDC)..........................8W-42-4
Fuse 15 (PDC)..........................8W-42-5
Heater Mode Switch.......................8W-42-3
Ignition Switch......................8W-42-3, 4, 5
Powertrain Control Module..................8W-42-4
Radiator Fan Motor.......................8W-42-5
Radiator Fan Relay.......................8W-42-5
8W - 42 - 2 8W-42 AIR CONDITIONING/HEATERÐXJ VEHICLESJ