brake light JEEP CHEROKEE 1988 Service User Guide

Fill master cylinder. Install vacuum bleed equipment to first
bleeder valve to be serviced. Open bleeder valve 3/4-1 turn. Depress
vacuum pump and pull fluid into reservoir jar. Bleed each bleeder
valve in sequence. See BLEEDING SEQUENCE table.
PRESSURE BLEEDING
1) Clean master cylinder cap and surrounding area. Remove
cap. With pressure tank at least 1/2 full, connect to master cylinder
with adapters. Attach bleeder hose to first bleeder valve to be
serviced. See BLEEDING SEQUENCE table.
2) Place other end of hose in clean glass jar partially
filled with clean brake fluid so end of hose is submerged in fluid.
The hold off valve must be positioned properly before pressure
bleeding (if equipped). See HYDRAULIC CONTROL VALVES under BRAKE
SYSTEM BLEEDING in this article.
3) Open release valve on pressure bleeder. Follow equipment
manufacturer's pressure instructions or see PRESSURE BLEEDER SETTINGS
table. Open bleeder screw 3/4-1 turn and note fluid flow.
4) Close bleeder screw when fluid flowing is free of bubbles.
Repeat procedure on remaining wheels in proper sequence. Check brake
pedal operation after bleeding has been completed.
5) Remove pressure bleeding equipment and valve retainer from
hold off valve. Ensure that master cylinder is full of fluid.
PRESSURE BLEEDER SETTINGS TABLE









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Application psi (kg/cm)
All Models ............................... 15-20 (1.1-1.4)









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MANUAL BLEEDING
NOTE: When bleeding disc brakes, air may tend to cling to caliper
walls. Lightly tap caliper, while bleeding, to aid in
removal of air.
1) Fill master cylinder. Install bleeder hose to first
bleeder valve to be serviced. See BLEEDING SEQUENCE table. Submerge
other end of hose in clean glass jar partially filled with clean brake
fluid. See Fig. 8.
2) Open bleeder valve 3/4-1 turn. Depress brake pedal slowly
through full travel. Close bleeder valve and release pedal. Repeat
procedure until flow of fluid shows no signs of air bubbles.
NOTE: When bleeding brake system manually, ensure bleeder valve is
closed when brake pedal is released.

Disassembly
Remove dust boots. Push pistons, piston cups and expander
spring out of bore. Discard cups. Clean all parts with brake solvent.
Inspect cylinder bore and piston for pitting, wear or damage. Replace
as necessary. Light scoring or pitting may be removed by honing.
Reassembly
1) Lubricate cylinder bore and internal components with brake
fluid. Do not lubricate dust boots. Position replacement piston cups
on spring expanders. Install assembled parts in cylinder bore.
2) Ensure expanders are seated in piston cups. Cups are to be
installed with lips facing each other. Install pistons with flat sides
facing interior of bore. Install dust boots.
TORQUE SPECIFICATIONS
TORQUE SPECIFICATIONS TABLE








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Application Ft. Lbs. (N.m)
Disc Brakes
Caliper Mounting Bolts ......................... 35 (47)
Bleeder Screw .................................. 12 (16)
Brake Line-to-Caliper .......................... 13 (18)
Drum Brakes
Wheel Cylinder Bolts ........................... 11 (15)
Bleeder Screw 1/4" ........................... 4-5 (5-7)
Bleeder Screw 3/8" ......................... 4-10 (5-14)
Brake Line ............................... 10-17 (14-23)
Backing Plate Bolt ....................... 30-40 (41-54)
Master Cylinder Retaining Nuts
Except Grand Wagoneer .......................... 20 (27)









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BRAKE SYSTEM SPECIFICATIONS
DISC BRAKE SPECIFICATIONS
DISC BRAKE SPECIFICATIONS TABLE








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Application In. (mm)
Cherokee, Comanche, Wagoneer & Wrangler
Disc Diameter ............................ 11.02 (279.9)
Lateral Runout ............................ 0.005 (0.13)
Parallelism ............................... 0.001 (0.03)
Original Thickness ......................... 0.88 (22.4)
Min. Refinish Thickness .................. 0.815 (20.70)
Discard Thickness ........................ 0.815 (20.70)
Grand Wagoneer
Disc Diameter ............................ 12.00 (304.8)
Lateral Runout ............................ 0.005 (0.13)
Parallelism ............................... 0.001 (0.03)
Original Thickness ................................. N/A
Min. Refinish Thickness .................. 1.215 (30.86)
Discard Thickness ........................ 1.215 (30.86)









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DRUM BRAKE SYSTEM SPECIFICATIONS
DRUM BRAKE SPECIFICATIONS TABLE

Removal (Cherokee, Comanche & Wagoneer)
Remove clutch assembly. Remove pilot bushing using Slide
Hammer (J-2619-01) and Bushing Remover (J-5822).
Installation
Lubricate replacement bushing with engine oil. Remove pilot
bushing lubricating wick and soak wick in engine oil. Install wick in
bushing bore. Install bushing using Clutch Pilot Shaft (J-33169). Keep\
pilot shaft parallel with crankshaft center line to prevent damage to
bushing. Reverse removal procedure to complete installation.
OVERHAUL
CLUTCH MASTER CYLINDER
Disassembly
1) Remove reservoir cap and cover. Remove push rod dust
cover. Remove snap ring holding push rod in cylinder bore. Discard
dust cover and snap ring.
2) Remove push rod, retaining washer, and seal as an
assembly. Discard seal. Remove plunger, valve spring, and valve stem
assembly from cylinder bore by tapping cylinder body on wood block.
3) Compress valve spring slightly. Pry tab of valve stem
retainer upward to release retainer, spring and stem assembly from
plunger. Remove seal from plunger and discard. Remove spring retainer
and valve stem from valve spring.
NOTE: Retainer tab is located in rectangular slot in side of stem
retainer.
4) Remove valve stem from retainer. Remove spring washer and
stem tip seal from end of valve stem. See Fig. 3. Discard stem tip
seal and spring washer. Clean parts with brake fluid or brake cleaning
solvent.
5) Inspect cylinder bore for wear, nicks or scores. Master
cylinder bore must be clean and smooth. Light discoloration is
acceptable. Replace if necessary. Clutch master cylinder must not be
honed under any circumstances.
Fig. 3: Exploded View Of Clutch Master Cylinder
Courtesy of Chrysler Motors.
Reassembly
1) Lubricate cylinder bore with brake fluid. Make sure lip of

CO M PU TE R R ELE A R N P R O CED URES

1988 J e ep C hero ke e
GENERAL INFORMATION
Computer Relearn Procedures
All Models
* PLEASE READ THIS FIRST *
The following general procedures are to be used if
driveability problems are encountered after power loss or battery has
been disconnected. These procedures may provide an aid in eliminating
these problems.
To reduce the possibility of complaints, after any service
which requires battery power to be disconnected, vehicle should be
road tested.
COMPUTER RELEARN PROCEDURES
Vehicles equipped with engine or transmission computers may
require a relearn procedure after vehicle battery is disconnected.
Many vehicle computers memorize and store vehicle operation patterns
for optimum driveability and performance. When vehicle battery is
disconnected, this memory is lost. The computer will use default data
until new data from each key start is stored. As computer memorizes
vehicle operation for each new key start, driveability is restored.
Vehicle computers may memorize vehicles operation patterns for 40 of
more key starts.
Customers often complain of driveability problems during
relearn stage because vehicle acts differently then before being
serviced. Depending on type and make of vehicle and how it is
equipped, the following complaints (driveability problems) may exist:
* Harsh Or Poor Shift Quality
* Rough Or Unstable Idle
* Hesitation Or Stumble
* Rich Or Lean Running
* Poor Fuel Mileage
These symptoms and complaints should disappear after a number
of drive cycles have been memorized. To reduce the possibility of
complaints, after any service which requires battery power to be
disconnected, vehicle should be road tested. If a specific relearn
procedure is not available, the following procedure may be used:
Automatic Transmission
* Set parking brake, start engine in "P" or "N" position.
Warm-up vehicle to normal operating temperature or until
cooling fan cycles.
* Allow vehicle to idle for one minute in "N" position. Select
"D" and allow engine to idle for one minute.
* Accelerate at normal throttle position (20-50%) until vehicle
shifts into top gear.
* Cruise at light to medium throttle.
* Decelerate to a stop, allowing vehicle to downshift, and use
brakes normally.
* Process may be repeated as necessary.
Manual Transmission

CRUIS E C O NTR O L S YSTE M

1988 J e ep C hero ke e
1988 Cruise Control Systems
JEEP CRUISE COMMAND
All Models
DESCRIPTION & OPERATION
Jeep vehicles use an electro-mechanical servo system. The
system consists of a control module, speed sensor, servo, control
switch assembly, vacuum storage canister, check valve and release
system. Release system consists of a mechanical vacuum vent valve and
brake and clutch (M/T) release switches.
Cruise control switch is an integral part of turn signal
switch lever and consists of 2 separate switches. First is an "ON-OFF"
and "RESUME" slide switch located on flat of directional switch lever.
Second is "SET/COAST" push button switch located at end of
directional switch lever. To engage system, move slide switch to "ON"
position and accelerate to desired speed. Depress and release
"SET/COAST" button on end of switch lever. System will now maintain
selected speed.
System will automatically disengage when brake or clutch
pedal is depressed. It can be re-engaged to previously selected speed
by accelerating to 30 MPH and moving slide switch to "RESUME"
position, then releasing switch.
NOTE: When slide switch is moved to "OFF" position, pre-set speed
of "RESUME" function is canceled from memory and must be
reset when system is reactivated.
Higher speed can be set by pressing on accelerator pedal
until new speed is reached and then pushing "SET/COAST" button. Lower
speed can be obtained by lightly depressing brake pedal, allowing the
vehicle to slow to desired speed and then depressing and releasing
"SET/COAST" button.
CONTROL MODULE
Control module receives input voltage representing vehicle
speed from speed sensor, which is driven by the speedometer cable.
Control module has a low speed circuit that prevents operation at
speeds below 30 MPH. See Fig. 1.
SERVO
Servo is controlled by control module and uses manifold
vacuum to control throttle. Bead-link chain connects servo cable to
throttle linkage. See Fig. 1.
CONTROL SWITCH
Control switch assembly is an integral part of turn signal
switch lever. See Fig. 1.
RELEASE SYSTEM
Release system deactivates cruise control system when brake
or clutch pedal is depressed. Either servo vent valve or mechanical
vacuum vent switch admits atmospheric pressure into servo when brake
pedal is depressed.

SYSTEM WILL NOT ENGAGE
Restricted vacuum hose or no vacuum. Control switch or
control module defective. Speed sensor defective. Clutch or brake
light switch defective or misadjusted. Brake light switch wire
disconnected. Open circuit between brake light switch and brake
lights.
RESUME FEATURE INOPERATIVE
Defective servo ground connection. Defective control switch.
ACCELERATE FUNCTION INOPERATIVE
Accelerate circuit in control module inoperative. Defective
control switch.
SYSTEM RE-ENGAGES WHEN BRAKE PEDAL IS RELEASED
Defective control module. Mechanical vent valve not opening.
Kink in mechanical vent valve hose. Brake light switch defective.
CARBURETOR THROTTLE DOES NOT RETURN TO IDLE POSITION
Improper linkage adjustment.
ROAD SPEED CHANGES 2 MPH OR MORE WHEN SETTING SPEED
Centering adjustment wrong. Servo link misadjusted.
ENGINE ACCELERATES WHEN STARTED
Improper servo chain adjustment. Vacuum hose connections
reversed at servo. Defective servo.
SYSTEM DISENGAGES ON LEVEL ROAD WITHOUT APPLYING BRAKES
Loose wire connection. Loose vacuum hose connection. Servo
linkage broken. Defective brake light switch.
ERRATIC OPERATION
Reverse polarity of system wiring. Defective servo. Defective
control module.
VEHICLE CONTINUES TO ACCELERATE WHEN "SET" BUTTON IS RELEASED
Servo or control module defective.
SYSTEM ENGAGES BUT SLOWLY LOSES SET SPEED
Air leak at connections or in vacuum hoses. Air leak on vent
valve on brake pedal.
ADJUSTMENTS
CONTROL MODULE ADJUSTMENT
NOTE: Control module adjustments are preset by manufacturer. If
other components in system appear to be functioning properly

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.

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