light JEEP CHEROKEE 1988 Service Service Manual

control module before starting diagnosis or repair procedure, as this
connection is disturbed when Cruise Command System Tester (AM PC-1-R)
is used. Poor connection at this point may be improperly diagnosed as
control module malfunction.
Brake light and clutch switches should be properly adjusted.
Ensure that all vacuum lines are correctly routed and tightly
connected.
CRUISE COMMAND SYSTEM TESTS
Testing is performed with Cruise Command System Tester (AM
PC-1-R). Remove wire harness connector from control module. Connect
tester to wire harness connector. Perform tests as part of service
diagnosis to determine cause and correction of system malfunction.
Various tester lights are associated with specific components,
circuits, etc.
CONTROL SWITCH CONTINUITY
Wrangler
NOTE: Voltage checks should show battery voltage. If resistance
readings are incorrect, check circuit for an open or a
short. Cruise control module terminal No. 1 grounds through
connector at engine block.
Light No. 1 "OFF" (Set Switch)
With control switch in "ON" position, check for battery
voltage between HAZ/STOP and in-line fuse, terminal No. 14 and ground
terminal No. 1
Light No. 2 "OFF" (Control Switch & Speed Sensor)
With control switch in "ON" position, check for battery
voltage between HAZ/STOP and in-line fuse, terminal No. 5 and ground
terminal No. 1. With ignition switch in "OFF" position, check
resistance between terminals No. 2 and No. 3. Resistance should be 15-
50 ohms.
Light No. 3 "OFF" (Brake Light Ground)
With ignition switch in "ON" position, install jumper wire
between terminals No. 7 and No. 13. If brake lights do not turn on,
check fuses and brake light switch connections.
Light No. 4 "OFF" (Throttle Position Feedback Sensor)
With ignition switch in "ON" position, check for battery
voltage between gauge fuses at terminals No. 7 and No. 1.
With ignition switch in "OFF" position, check resistance
between terminals No. 2 and No. 11. Resistance should be 2400-4000
ohms. At idle resistance should be 2800-4300 ohms and at wide open
throttle resistance should be 4000 ohms.
Light No. 5 "OFF" (Resume/Accel/Vent Valve)
With control switch in "RESUME/ACCEL" position, check for
battery voltage between HAZ/STOP and in-line fuse, terminal No. 10 and
ground terminal No. 1. With ignition switch in "OFF" position, check
resistance between terminals No. 6 and No. 12. Resistance should be
30-50 ohms. Resistance between terminals No. 6 and ground, and
terminal No. 12 and ground should be infinite (open).
Light No. 6 "OFF" (Resume/Accel/Charge Valve)
With control switch in "RESUME/ACCEL" position, check for
battery voltage between HAZ/STOP and in-line fuse, terminal No. 10 and
ground terminal No. 1. With ignition switch in "OFF" position, check
resistance between terminals No. 4 and No. 12. Resistance should be

30-50 ohms. Resistance between terminals No. 4 and ground, and
terminal No. 12 and ground should be infinite (open).
WRANGLER CRUISE CONTROL TESTING









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Conditions Lights "ON"
Control Switch "ON" & Set Switch Depressed .................. No. 1
Control Switch "ON" ......................................... No. 2
Ignition "ON" & Brake or Clutch Pedal Depressed ..... No. 3 & No. 4
Cruise Control & Resume/Accel "ON" .................. No. 5 & No. 6
Cruise & Resume/Accel "ON" & Engine Running (1) ..... No. 5 & No. 6
( 1) - Servo will pull throttle wide open. Keep RPM at a safe level by
releasing cruise control switch.









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Except Wrangler
Use 12-volt test light to test control switch continuity.
Connect test light to wires as indicated in CONTROL SWITCH CONTINUITY
TEST CHART. See Figs. 3 or 4.
Fig. 3: Cherokee, Comanche & Wagoneer Control Switch Continuity Test
Chart
Courtesy of Chrysler Motors.

Fig. 4: Grand Wagoneer Control Switch Continuity Test Chart
Courtesy of Chrysler Motor.
CORRECT POWER SOURCE
Cherokee, Comanche & Wagoneer
1) With ignition switch and control switch "OFF", all test
lights should be off. If any light is on, check Brown (7) wire is not
connected directly to source of voltage.
2) Check for bad control switch. With ignition switch in
"OFF" position, and control switch "ON". Light No. 2 should be on and
lights No. 1, 3, 4, 5 and 6 should be off.
3) If light No. 2 is off, check speed sensor continuity,
check speed sensor terminals to Gray and Drk. Blue wires, and check
that terminals No. 2, 3, 5 and 7 (Gray, Drk. Blue and Lt. Green wires
are not grounded).
Grand Wagoneer

With ignition and control switches in "OFF" position, test
lights should be off. If one or more lights are on, remove Brown (5)
wire at control module connector and check for direct source of
voltage or repair defective control switch.
SYSTEM ELECTRICAL CONTINUITY
Cherokee, Comanche & Wagoneer
1) With ignition and control switches in "ON" position,
lights No. 2, 3 and 4 should be on. Lights No. 1, 5 and 6 should be
off. If light No. 2 is off, check speed sensor continuity, check speed
sensor terminals to Gray and Drk. Blue wires, and check terminals No.
2, 3, 5 and 7 (Gray, Drk. Blue and Lt. Green wires are not grounded).
2) If light No. 3 is off, check brake light switch and all
Brown, Lt. Blue and Lt. Green wire connections. If light No. 4 is off,
check terminals No. 2 and No. 11 at control module connector. Check
continuity of throttle position feedback rheostat of servo.
Grand Wagoneer
1) With ignition and control switches in "ON" position,
lights No. 1, 2, 3, and 4 should be on. Lights No. 5 and 6 should be
off. If light No. 1 is off, check for blown fuse in brake light switch
to control switch circuit. Check Red, Brown and Green wires at control
switch for continuity to switch. Check Drk. Green wire (14) at control\
module connector for continuity to control module.
2) If light No. 2 is off, check speed sensor for correct
output voltage. Check Gray and Drk. Blue wire at speed sensor
connector for continuity to control module connector. Check terminals
No. 2, 3, 5 and 7 at control module connector for proper connection to
wires.
3) If light No. 3 is off, check brake and clutch switch
adjustment. If light No. 4 is off, check for defective connection at
terminals No. 2 and 11 on control module connector. Check operation of
throttle position feedback rheostat on servo.
COAST CONTINUITY TEST
Cherokee, Comanche & Wagoneer
1) With ignition and control switches in "ON" position,
depress and hold "SET/COAST" button. Lights No. 1, 2, 3 and 4 should
be on. Lights No. 5 and 6 should be off. If light No. 1 is off, check
voltage from brake light switch, check 4-amp in-line fuse of Pink
wire, and check Pink, Brown and Drk. Green wires at control switch
connector and Drk. Green (14) wire at control module connector for
good connections.
2) If light No. 2 is off, check speed sensor continuity,
check speed sensor terminals to Gray and Drk. Blue wires, and check
terminals No. 2, 3, 5 and 7 (Gray, Drk. Blue and Lt. Green wires) for
ground.
3) If light No. 3 is off, check brake light switch, check all
Brown, Lt. Blue and Lt. Green wire connections. If light No. 4 is off,
check terminals No. 2 and 11 at control module connector, and check
continuity of throttle position feedback rheostat of servo.
SERVO CHARGE VALVE SOLENOID CONTINUITY
CAUTION: If engine is running, servo will move throttle to wide open
position.
Grand Wagoneer
1) With ignition and control switches in "ON" position,
depress and hold "SET/COAST" button. Lights No. 2, 3, 4, 5 and 6
should be on. Light No. 1 should be off. Light No. 4 will dim when

servo moves throttle to wide open position with engine operating.
2) If light No. 2 is off, check speed sensor for correct
output voltage. Check Gray and Drk. Blue wire at speed sensor
connector for continuity to control module connector. Check terminals
No. 2, 3, 5 and 7 at control module connector for proper connection to
wires.
3) If light No. 3 is off, check brake and clutch switch
adjustment. If light No. 4 is off, check for defective connection at
terminals No. 2 and 11 on control module connector. Check operation of
throttle position feedback rheostat on servo.
4) If light No. 5 is off, check for defective connections at
terminals No. 4 and 12 on control module connector. If necessary,
replace defective servo. If light No. 6 is off, check for defective
connection at terminals No. 6 and 12 on control module connector. If
necessary, replace defective servo.
5) If all lights are off after depressing set/coast speed
switch, check for blown fuse. Check for short circuits in Red, Pink
and Brown wire circuits at control switch. If necessary, replace
defective servo.
SYSTEM DISENGAGEMENT WITH BRAKE PEDAL DEPRESSED
Cherokee, Comanche & Wagoneer
1) With ignition and control switches in "ON" position and
brake pedal depressed, lights No. 2 and 4 should be on. Lights No. 1,
3, 5 and 6 should be off. Light No. 3 should be on when brake pedal is
released.
2) If light No. 2 is off, check speed sensor continuity,
check speed sensor terminals to Gray and Drk. Blue wires, and check
terminals No. 2, 3, 5 and 7 (Gray, Drk. Blue and Lt. Green) for
ground.
3) If light No. 4 is off, check terminals No. 2 and 11 at
control module connector, and check continuity of throttle position
feedback rheostat of servo.
Grand Wagoneer
1) With ignition and control switches in "ON" position and
brake pedal depressed, lights No. 1, 2 and 4 should be on. Lights No.
3, 5 and 6 should be off. Light No. 3 should be on when brake pedal is
released.
2) If light No. 1 is off, check for blown fuse in brake light
switch to control switch circuit. Check Red, Brown and Green wires at
control switch connector for continuity to switch. Check Drk. Green
wire (14) at control module connector for continuity to control
module.
3) If light No. 2 is off, check speed sensor for correct
output voltage. Check Gray and Drk. Blue wire at speed sensor
connector for continuity to control module connector. Check terminals
No. 2, 3, 5 and 7 at control module connector for proper connection to
wires.
4) If light No. 4 is off, check for defective connection at
terminals No. 2 and 11 on control module connector. Check operation of
throttle position feedback rheostat on servo. If light No. 3 is off
when brake pedal is released, check brake light switch adjustment.
"RESUME/ACCEL" FUNCTION
CAUTION: If engine is running, servo will move throttle to wide open
position.
Cherokee, Comanche & Wagoneer
1) With ignition and control switches in "ON" position, slide
and hold control switch in "R/A" position. Lights No. 2, 3, 4, 5 and 6

should be on. Light No. 1 should be off. Light No. 4 will dim when
servo moves throttle to wide open position, if engine is running.
2) If light No. 2 is off, check speed sensor terminal
connections to control module through Gray and Drk. Blue wires. Check
terminals No. 2, 3, 5 and 7 (Gray, Drk. Blue and Lt. Green wires) for
ground.
3) If light No. 3 is off, check brake light switch, and check
all Brown, Lt. Blue and Lt. Green wire connections. If light No. 4 is
off, check terminals No. 2 and 11 at control module connector. Check
continuity of throttle position feedback rheostat of servo.
4) If light No. 5 is off, check for bad connection at White
(6) and Orange (12) wire terminals. If necessary, replace defective
servo.
5) If all lights are off after moving control switch to "R/A"
position, check for blown fuse or fuses, and check Red, Pink, Brown or
White wires for shorts. If necessary replace defective servo.
Grand Wagoneer
1) With ignition and control switches in "ON" position, slide
control switch to "R/A" position. All test lights should be on. Light
No. 4 will dim when servo moves throttle to wide open position, if
engine is running.
2) If light No. 1 is off, check for blown fuse in brake light
switch to control switch circuit. Check Red, Brown and Green wires at
control switch for continuity to switch.
3) If light No. 2 is off, check Gray and Drk. Blue wire at
speed sensor connector for continuity to control module connector.
4) If light No. 3 is off, check brake light switch
adjustment. If light No. 4 is off, check for defective connection at
terminals No. 2 and 11 on control module connector. Check operation of
throttle position feedback rheostat on servo.
5) If light No. 5 is off, check for defective connections at
terminals No. 4 and 12 on control module connector. If necessary,
replace defective servo. If light No. 6 is off, check for defective
connection at terminals No. 6 and 12 on control module connector. If
necessary, replace defective servo.
6) If all lights are off after moving control switch to "R/A"
position, check for blown fuse. Check for short circuits in Red, Pink
and Brown wire circuits at control switch. If necessary, replace
defective servo.
SPEED SENSOR TEST
1) Disconnect wire harness connector at speed sensor. Connect
a voltmeter (set on low AC scale) to terminals from speed sensor.
2) Raise front and rear wheels of vehicle off ground and
support vehicle with safety stands. Run engine (wheels spinning
freely) at 30 MPH and note voltage.
3) Voltage should be approximately .9 volts. Increases of .1
volts per each 10 MPH increase in speed should also be noticed. Turn
off engine and stop wheels. Lower vehicle. Connect speed sensor wire
harness.
SERVO TEST
1) With ignition switch in "OFF" position, disconnect servo
wire harness connector. Remove vacuum hose from brake pedal vent valve
nipple on servo. Disconnect servo cable from throttle linkage at
carburetor.
2) Connect an ohmmeter between ground and Red. Ground and
Orange. And Ground and White wire terminals of servo wire harness
connector. See Fig. 5. Observe ohmmeter during each test. An infinite
(open circuit) resistance should be indicated for each wire terminal.

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DEFO GGER - R EA R W IN DO W

1988 J e ep C hero ke e
1988 Defoggers
REAR WINDOW
Jeep: All Models
DESCRIPTION & OPERATION
System consists of 2 vertical bus bars and horizontal rows of
heating elements fused to inside of glass, a control switch, an
indicator light, and timer relay.
The grid feed wire is connected to bus bar on driver's side
of window. Ground bus bar is on right side of vehicle. Timer/relay
receives current from fuse block. A circuit breaker protects defogger
circuit.
NOTE: On some Jeep models, defogger switch and electric tailgate
switch are serviced as an assembly.
TROUBLE SHOOTING
NOTE: Control switch testing is not available for Wrangler models.
1) On Cherokee, Comanche and Wagoneer models, turn ignition
switch to "ON" position. Check for current at "I" and "B" terminals.
See Fig. 1 . If there is no current, check circuit and repair as
necessary. Make sure that switch has a good ground through wire
connected to "G" terminal.
2) With a good ground circuit and ignition switch in "ON"
position, current should be present at "L" terminal. If there is no
current, replace control switch.
Fig. 1: Jeep Control Switch Terminals
3) On Grand Wagoneer models, turn ignition switch to "ON"
position and press defogger switch. Separate wiring harness at
connector under dash. Connect a 12-volt test light from Purple wire to

ground. Test light should light. Turn defogger switch to "OFF"
position. Test light should not light.
GRID
1) Using a voltmeter with a 0-15 volt range, contact bus bar
connecting grid lines on passenger's side of glass with negative lead
of voltmeter. Contact driver's side bus bar with positive lead.
2) Turn ignition and control switches to "ON" position.
Reading should be 10-14 volts. Lower voltage indicates a poor ground.
Attach negative voltmeter lead to ground. Voltage reading should not
vary.
3) Contact negative lead to passenger's side bus bar. Probe
each grid line at midpoint with positive lead. A 6-volt reading
indicates line is good. A zero volt reading indicates a break between
midpoint and driver's side bus bar line.
4) A 10-14 volt reading indicates a break between midpoint
and passenger's side bus bar line. Move positive lead toward break and
voltage will change when break is crossed.
NOTE: On some Jeep models feed wire and ground wires a reversed.
Fig. 2: Grid Continuity Voltage Drop
RELAY
NOTE: No relay testing is available for Wrangler models.

Plate (J 23781-7) in bottom side gear. Install grease in centering
hole of step plate. Position Rotating Tool (J 23781-3) on step plate
tool. Coat threads of Forcing Screw (J 8646-2) with oil.
2) Insert forcing Screw (J 8646-2) through case and thread
into rotating tool. Thread screw through tool until it contacts
centering hole in step plate. Tighten forcing screw to relieve clutch
pack tension from pinions. Remove pinion thrust washers.
3) Tighten forcing screw until all clutch pack tension is
relieved from pinions. Slide rotating tool pawl so it engages with
side gear teeth. Rotate side gears with rotating tool until pinions
can be removed through case opening.
4) Remove forcing screw, rotating tool, upper side gear and
clutch pack. Remove differential case from axle shaft. Remove
remaining side gear, clutch pack and step plate tool. Remove retainer
clips from clutch packs. Mark clutch packs for reassembly reference.
Using a press, remove differential bearings.
Cleaning & Inspection
Clean all parts and dry with compressed air. If any clutch
plates or discs require replacement, all plates and discs should be
replaced. Replace any worn or damaged components.
NOTE: For adjustment procedures, see DANA SEMI-FLOATING or
FULL FLOATING AXLE articles in this section
Reassembly
1) Lightly lubricate clutch pack discs with axle lubricant.
Assemble clutch pack discs and install retaining clips on ears of
discs. See Fig. 3. Install assembled clutch packs on side gears.
Fig. 3: Typical Clutch Pack Assembly
2) Mount differential case on axle shaft. Install first
clutch pack and side gear in bottom bore of case. Ensure retaining
clips remain seated in case pockets. Install Step Plate (J 8646-2) in

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DO OR L O CKS - P O W ER

1988 J e ep C hero ke e
1988 Power Door Locks
JEEP
DESCRIPTION
Jeep vehicles with power door locks use a motor-actuated lock
system, controlled by rocker switches. Operation of switch assembly
controls the actuator motor.
Power door locks are protected by a 30-amp circuit breaker
located in the fuse block. Power door locks will not operate from
outside the vehicle.
TESTING
SWITCH
Using ohmmeter, test switches for continuity. Connect
ohmmeter across terminals as shown. See Fig. 1. Continuity should
exist between terminals in all positions.
Fig. 1: Checking Switch Continuity
Courtesy of Chrysler Motors.
ACTUATOR MOTOR
Connect ammeter to actuator motor terminals. Operate door
switch and note reading. Current draw should not exceed 8 amps at room
temperature. Actuator should complete full travel within one second.
Replace actuator motor if not within specification.
CIRCUIT BREAKER
1) Disconnect harness connector from fuse block. Using test
light, check fuse block harness connection for voltage. If there is no
battery voltage at connection, check for burnt fusible link in engine
compartment.
2) Check circuit breaker continuity if voltage exists. Using
ohmmeter, test circuit breaker for continuity. Replace circuit breaker
if no continuity exists.
3) If circuit breaker tests okay, check for battery voltage
at circuit breaker connection of fuse block with wiring harness
installed. If voltage exists at wiring harness but not at circuit
breaker connection, check fuse block for damage.
REMOVAL & INSTALLATION