1988 JEEP CHEROKEE wiring

connector. Connect negative voltmeter lead to terminal "D" and
positive voltmeter lead to terminal "A" to check input voltage. DO NOT
disconnect TPS connector.
3) Hold throttle plate closed against idle stop and note
voltage. Input voltage should be approximately 5 volts. Disconnect
voltmeter positive lead and connect to terminal "B" to measure output
voltage.
4) With throttle plate closed, measure the output voltage.
The output voltage should be approximately .2 volts. If output voltage
is not within specification, loosen TPS retaining screws.
5) Partially tighten one retaining screw. Rotate TPS to
obtain correct output voltage. Tighten retaining screws once correct
voltage is obtained.
Manual Transmission
1) Turn ignition on. Connect voltmeter through back of wiring
harness connector. Connect negative voltmeter lead to terminal "B" and
positive voltmeter lead to terminal "C". DO NOT disconnect TPS
connector. See Fig. 4.
2) Rotate and hold throttle plate in wide open position.
Ensure throttle linkage contacts stop. Note voltmeter reading. Voltage
reading should be 5 volts at wide open throttle. Return throttle plate
to closed throttle position. Disconnect voltmeter positive lead from
sensor terminal "C" and connect it to terminal "A".
3) Rotate and hold throttle plate in wide open position.
Ensure throttle linkage contacts stop. Note voltmeter reading. Output
voltage should be 4.6-4.7 volts. If voltage is not as specified,
loosen sensor mounting screw. Loosen upper sensor mounting screw for
small adjustments and lower screw for large adjustments.
4) Adjust sensor. Tighten sensor mounting screws. Remove
voltmeter and return throttle plate to closed position. Replace sensor
if specified output voltage cannot be obtained.
Fig. 4: Adjusting Throttle Position Sensor (Man Trans)
Courtesy of Chrysler Motors.
IDLE MIXTURE ADJUSTMENT

wires connected to switch). Disconnect distributor vacuum advance hose
and connect hose to vacuum switch. Disconnect wire connector from
knock sensor, located in cylinder head.
3) Using a jumper wire, ground knock sensor wire connector to
engine block. Start engine. With engine at idle speed (solenoid
energized), check timing. Adjust timing to one degree more than
specification (if required). See Emission Control Label.
IGNITION TIMING SPECIFICATIONS (DEGREES BTDC@RPM) - 4.2L









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Application Man. Trans. Auto. Trans.
50 State ............. 9 @ 1600 ............... 9 @ 1600
High Altitude ........ 16 @ 1600 ............. 16 @ 1600









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HOT (SLOW) IDLE RPM
4.0L
1) Apply parking brake and place transmission in Neutral
(Drive for automatic transmissions). Operate engine to normal
operating temperature. Turn ignition off.
2) Ensure all accessories are off. Connect positive
tachometer lead to terminal "D1-1" and negative lead to "D2-7" of
diagnostic connectors. See Fig. 3. Disconnect air stepper motor
connector and TPS wiring connector. See Fig. 4.
Fig. 3: Diagnostic Connector Terminal Identification
Courtesy of Chrysler Motors.

or vehicle fails emissions testing.
IDLE MIXTURE (TACHOMETER (LEAN DROP) PROCEDURE)
NOTE: On 4.2L engines, ensure idle speed and timing are set prior
to adjusting the idle mixture. If mixture adjustment time
exceeds 3 minutes, run engine at 2000 RPM in Neutral for one
minute, and resume adjustment. On 4.0L engines, idle mixture
adjustment is not possible.
4.2L
1) Remove carburetor and locate roll pins blocking idle
mixture screws. Drill through throttle body on closed end of roll pin
hole. Drive pins out with punch. Reinstall carburetor. Install
tachometer.
2) Operate engine to normal operating temperature, and adjust
curb idle speed. Place automatic transmission selector in Drive
(Neutral for manual transmissions). Turn mixture screws inward until
RPM drops. Turn screws outward until highest RPM is reached.
3) Turn mixture screws inward to obtain the correct decrease
in RPM. See LEAN DROP (RPM) table. Adjust both screws equally. When
mixture is correctly adjusted, replace roll pin to block adjustment
screws.
NOTE: If final RPM differs more than 30 RPM from specified curb
idle speed, reset curb idle, and repeat mixture adjustment.
LEAN DROP (RPM) TABLE









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Application Man. Trans. Auto. Trans.
4.2L .................... 50 ........................ 50









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THROTTLE POSITION SENSOR (TPS)
NOTE: Adjustment of TPS only applies to the 4.0L models. It may be
necessary to remove throttle body from intake manifold, to
access sensor wiring harness.
Checking & Adjusting - 4.0L (Automatic Transmission)
1) Locate the square TPS connector. Note connector terminal
identification stamped on the back of the connector. Turn ignition on.
2) Connect voltmeter through back of wiring harness
connector. Connect negative voltmeter lead to terminal "D" and
positive voltmeter lead to terminal "A" to check input voltage. DO NOT
disconnect TPS connector.
3) Hold throttle plate closed against idle stop and note
voltage. Input voltage should be approximately 5 volts. Disconnect
voltmeter positive lead and connect to terminal "B" to measure output
voltage.
4) With throttle plate closed, measure the output voltage.
The output voltage should be approximately 4.2 volts. If output
voltage is not within specification, loosen TPS retaining screws.
5) Partially tighten one retaining screw. Rotate TPS to
obtain correct output voltage. Tighten retaining screws once correct
voltage is obtained.
Checking & Adjusting - 4.0L (Manual Transmission)
1) Turn ignition on. Connect voltmeter through back of wiring
harness connector. Connect negative voltmeter lead to terminal
"B" and positive voltmeter lead to terminal "A". DO NOT disconnect TPS
connector.

TU RN S IG NALS & H AZA R D F LA SH ER S

1988 J e ep C hero ke e
1988 Turn Signal & Hazard Light Systems
JEEP
DESCRIPTION
Turn signals and hazard flashers systems use a common turn
signal/hazard light switch assembly mounted within upper steering
column housing.
FLASHER LOCATIONS
Hazard
Mounted on fuse block.
Turn Signal
Mounted on fuse block.
TROUBLE SHOOTING
NOTE: Following trouble shooting is only information available
from manufacturer.
Hazard Lights (Comanche, Cherokee & Wagoneer)
If lights do not come on with hazard switch turned on, check
hazard/stop light fuse by operating stop lights. If fuse is okay,
check turn signal flasher, turn signal/hazard switch, and related
wiring. If only one hazard light does not work, check bulb.
Turn Signals (Comanche, Cherokee & Wagoneer)
If all turn signals do not work, check turn/back-up light
fuse by operating back-up lights. If fuse is okay, check turn signal
flasher, turn signal/hazard switch, and related wiring. If only one
turn signal does not work, check bulb.
TESTING
NOTE: Following trouble shooting is only information available
from manufacturer.
Hazard Indicators (Wrangler)
1) Turn ignition and hazard warning switch "ON". Check for
pulsating voltage at Light Blue (left indicator) and Dark Blue (right\
indicator) wires. If voltage is present, go to next step. If voltage
is not present, replace turn signal switch.
2) Remove bulbs for turn signal indicators. Measure
resistance across bulb terminals. If resistance is zero ohms, replace
light bulb(s). If resistance readings are not zero ohms, go to next
step.
3) Check for pulsating voltage at battery side of bulb
sockets. If voltage is present, go to next step. If voltage is not
present, repair open circuit between socket and turn signal switch
steering column connector.
4) Turn ignition off and check resistance on ground side of
bulb sockets. If resistance is zero ohms, hazard indicator circuit is
okay. If resistance reading is not zero ohms, repair open in ground
circuit.
Hazard Lights (Wrangler)

\003
WIP ER /W ASH ER S YSTE M

1988 J e ep C hero ke e
1988 Wiper/Washer Systems
JEEP
All Models
DESCRIPTION
Jeep vehicles use a 2-speed electric motor, which is a
compound wound (series and shunt) type. A crank arm, attached
externally to gear shaft, operates linkage which activates wiper
blades.
All models have an optional intermittent feature. All models
use an electric washer system consisting of a motor, reservoir, and
necessary hoses and nozzles.
Some Cherokee and Wagoneer models are equipped with rear
wipers. The rear motor is a single-speed motor with an automatic park
feature. The circuit is protected by a separate 4.5-amp circuit
breaker attached to brake pedal support.
TROUBLE SHOOTING
WIPER INOPERATIVE OR OPERATES AT ONE SPEED ONLY
1) If wiper does not operate on either speed, check for
binding or interference of linkage. If okay, place wiper switch on
"LO" and then on "HI" setting. Connect a test light between terminals
of wiring harness plug that connects to motor.
2) Check for power at White wire with tracer and Black
(ground) wire terminal for low speed. Check between Dk. Blue with
tracer and Black wire terminal for high speed.
3) If light does not glow, check ignition switch, wiper
switch, harness or terminals for open circuits. If light glows, check
for loose or misaligned connection between wiring harness plug and
motor plug. If okay, replace wiper motor.
WIPERS DO NOT PARK
1) Disconnect motor and connect Gray lead to White lead.
Apply 12 volts to Blue lead. Replace motor if it fails to park. If it
parks, turn ignition switch on, and wiper switch to "PARK".
2) Connect a test light to Lt. Green wire with tracer and to
ground at motor plug.
3) Check continuity between Tan wire with tracer and White
wire with tracer.
4) If test light does not glow, check harness connections
between motor and instrument panel switch. If okay, replace panel
switch. If not okay, repair harness connection.
WIPER MOTOR QUITS WHILE WIPING
1) With engine idling and blower motor on high, operate
wipers at high speed setting for 5 cycles consisting of 3 seconds of
water and 57 seconds of drying.
2) If motor struggles to a complete stop, clean glass and
replace blades. Repeat test. If motor stops, test circuit breaker in
panel switch. If motor stopped suddenly in original test, check
circuit breaker. Repeat test. If motor stops, replace motor.

ALL FUNCTIONS OKAY EXCEPT INTERMITTENT WIPE
1) If blades stop and start erratically, test circuit
breaker. If okay, check wiper switch continuity. If continuity is
present, check continuity of wiring between switch, governor and
ground. Repair wiring or replace governor as necessary.
2) If operation is intermittent on low speed only, check for
loose connections at governor by disconnecting governor and connecting
switch directly to instrument panel harness.
3) If all functions except pulse and mist work, replace
governor. If functions are not okay, recheck wiring and replace
governor.
WINDSHIELD WASHER DOES NOT OPERATE
1) If motor runs but does not pump, check fluid level. If
level is okay, check for split, loose, pinched or kinked hoses. Check
for restrictions at nozzles. Check for reversed wire leads to motor.
2) If motor does not run, check for blown fuse. Replace fuse,
if necessary. If fuse is okay, disconnect plug at reservoir and check
for power by connecting a test light across connector terminals.
Energize washer circuit by closing washer and ignition switches.
3) If no power is present, check for open ground wire or
defective wiper/washer switch. Repair or replace as necessary. If
power is present, reconnect plug to motor and check for tight
connection. If motor does not run, replace pump motor.
REMOVAL & INSTALLATION
REAR WIPER SWITCH
Removal & Installation
Remove instrument panel bezel and switch housing panel.
Disconnect switch connector, slightly depress switch mounting tabs and
remove switch. To install, reverse removal procedure.
REAR WIPER MOTOR
Removal & Installation
1) Remove wiper arm from pivot pin by depressing tab and
pulling arm straight out. Disconnect washer hose. Remove pivot pin
retaining nut and interior trim panel. Remove rear wiper motor
attaching screws and remove wiper motor.
2) To install, reverse removal procedure. Wiper blade should
be parallel to window in parked position (3/8-3/4" from bottom of
window) and come no closer than 3/16" to window seal when operated on
a wet window.
WINDSHIELD WIPER MOTOR
Removal & Installation
Remove wiper arm assemblies by lifting blades off windshield
and pulling out tab that locks blade in up position. Remove cowl trim
panel. Disconnect washer hose. Remove cowl mounting bracket attaching
nuts and pivot pin screws. Disconnect wiring harness and remove wiper
motor. To install, reverse removal procedure.

WIR IN G D IA G RAM S YM BO LS

1988 J e ep C hero ke e
WIRING DIAGRAMS
How To Use The Wiring Diagrams
WIRING DIAGRAMS
INTRODUCTION
The wiring diagrams and technical service bulletins,
containing wiring diagram changes, are obtained from the domestic and
import manufacturers. These are checked for accuracy and are all
redrawn into a consistent format for easy use.
All diagrams are arranged with the front of the vehicle at
the left side of the first page and the rear of the vehicle at the
right side of the last page. Accessories are shown near the end of the
diagram.
Components are shown in their approximate location on the
vehicle. Due to the constantly increasing number of components on
vehicles today, it is impossible to show exact locations.
In the past, when cars were simpler, diagrams were simpler.
All components were connected by wires, and diagrams seldom exceeded 4
pages in length. Today some wiring diagrams require more than 16
pages. It would be impractical to expect a service technician to trace
a wire from page 1 across every page to page 16.
Removing some of the wiring maze reduces eyestrain and time
wasted searching across several pages. Today, the majority of diagrams
now follow a much improved format, which permits space for internal
switch details and connector shapes.
Any wires that don't connect directly to their components are
identified on the diagram to indicate where they go. There is a legend
on the first page of each diagram, detailing component location. It
refers you to sub-systems, using grid NUMBERS at the top and bottom of
the page and grid LETTERS on each side. This grid system works in a
manner similar to that of a road map.
HOW TO USE THE WIRING DIAGRAMS
1) On the first page of the diagram, you will find a listing
of major electrical components or systems. Locate the specific
component or system you wish to trace. A grid number and letter will
follow the component's name.
2) Use the grid NUMBERS (arranged horizontally across the top\
and bottom of each page) to find the page of the wiring diagram that
contains the component you're seeking. When you reach this page, use
the grid LETTERS on the side of the page to determine the component's
vertical location.
3) Locate the circuit you need to service. The internals are
shown for switches and relays to assist you in understanding how the
circuit operates.
NOTE: In some of the newer wiring diagram articles in this
product, there is a Legend for the wiring diagrams that has
been created to make locating components easier. For these
articles, there will be a COMPONENT LOCATION MENU title in
the article main menu. These articles will also have the
original legend available on the first graphic.

Fig. 1: Identifying Tie-Off Symbols
4) If the wires are not drawn all the way to another
component (across several pages), a reference will tell you their
final destination.
5) Again, use the legend on the first page of the wiring
diagram to determine the grid number and letter of the referenced
component. You can then turn directly to it without tracing wires
across several pages.
6) The symbols shown in Fig. 1 are called tie-offs. The first
tie-off shown indicates that the circuit goes to the temperature
sensor, and is also a ground circuit.
7) The second symbol indicates that the circuit goes to a
battery positive parallel circuit. The third symbol leads to a
particular component and the location is also given.
8) The lines shown in Fig. 2 are called options. Which path
or option to take depends on what engine or systems the vehicle has.