1995 JEEP YJ body components

ABS OPERATION AND SERVICE
INDEX
page page
ABS Component Serviceability............... 37
ABS Diagnostic Connector.................. 35
ABS Operation in Antilock Braking Mode........ 36
ABS Operation in Normal Braking Mode........ 35
ABS System Power-Up and Initialization........ 35
Acceleration Switch........................ 35
Acceleration Switch Installation............... 39
Acceleration Switch Operation................ 37
Acceleration Switch Removal................ 39
Combination Valve........................ 34
ECU Installation (XJ Models)................. 40
ECU Operation........................... 37
ECU Removal (XJ Models).................. 40
ECU Removal/Installation (YJ Models).......... 41
Electronic Control Unit (ECU)................ 34
Front Wheel Sensor Installation............... 38
Front Wheel Sensor Removal................ 38HCU Installation (XJ)....................... 43
HCU Installation (YJ)....................... 44
HCU Operation........................... 36
HCU Removal (XJ)........................ 41
HCU Removal (YJ)........................ 44
Hydraulic Control Unit (HCU)................. 33
Ignition Switch........................... 35
Master Cylinder/Power Brake Booster.......... 34
Rear Wheel Sensor Installation and Adjustment . . . 38
Rear Wheel Sensor Removal................ 38
Speed Sensor Air Gap..................... 37
System Description........................ 33
System Relays........................... 35
System Warning Light...................... 35
Wheel Speed Sensor Operation.............. 37
Wheel Speed Sensors..................... 34
SYSTEM DESCRIPTION
The Jeep antilock brake system (ABS) is an elec-
tronically operated, all wheel brake control system.
The system is designed to prevent wheel lockup
and maintain steering control during periods of high
wheel slip when braking. Preventing lockup is accom-
plished by modulating fluid pressure to the wheel
brake units.
The hydraulic system is a three channel design.
The front wheel brakes are controlled individually
and the rear wheel brakes in tandem (Fig. 1). The
ABS electrical system is separate from other electri-
cal circuits in the vehicle. A specially programmed
electronic control unit (ECU) operates the system
components.
ABS system major components include:
²hydraulic control unit (HCU)
²electronic control unit (ECU)
²wheel speed sensors and axle shaft tone rings
²acceleration switch
²main relay and pump motor relay
²ABS warning light
²pump motor sensor
HYDRAULIC CONTROL UNIT (HCU)
The hydraulic control unit (HCU) consists of a
valve body, pump body, accumulators, pump motor,
and wire harnesses (Fig. 2).
The pump, motor, and accumulators are combined
into an assembly attached to the valve body. The ac-
cumulators store the extra fluid released to the sys-
tem for ABS mode operation. The pump provides the
fluid volume needed and is operated by a DC type
motor. The motor is controlled by the ECU.The valve body contains the solenoid valves. The
valves modulate brake pressure during antilock brak-
ing and are controlled by the ECU.
The HCU provides three channel pressure control
to the front and rear brakes. One channel controls
the rear wheel brakes in tandem. The two remaining
channels control the front wheel brakes individually.
During antilock braking, the solenoid valves are
opened and closed as needed. The valves are not static.
They are cycled rapidly and continuously to modulate
pressure and control wheel slip and deceleration.
Fig. 1 Jeep ABS System
JABS OPERATION AND SERVICE 5 - 33

(2) Align and attach harness connector to ECU.
Slide connector into engagement with tangs on ECU.
Then tilt connector downward and into engagement
with ECU pin terminals. Exercise care as pin termi-
nals can be damaged if connector is forced into place.
(3) Connect harness to security alarm module, if
equipped.
(4) Position ECU bracket under instrument panel.
(5) Install and tighten ECU mounting bracket
bolts/nuts to 8-14 Nzm (75- 125 in. lbs.) torque.
(6) Install trim panel on instrument panel, if re-
moved.
ECU REMOVAL/INSTALLATION (YJ MODELS)
The antilock ECU is attached to the dash panel in-
side the passenger compartment. It is positioned just
above the heater/air conditioning plenum housing, in
line with the glove box (Fig. 16).
The ECU is attached to the dash panel by bolts
and nuts that are accessible from the engine com-
partment. The fasteners are located just to the right
of the battery.
On models with air conditioning, it will be neces-
sary to remove the air conditioning fascia panel and
ducts for access to the ECU and harness connecter.
HCU REMOVAL (XJ)
A new design HCU is used in 1995 models. The
new HCU has built-in accumulators that store the
extra fluid released for antilock mode operation. As a
result, the master cylinder and HCU are no longer
interconnected by hoses.The 1995 and prior hy-
draulic control units are NOT interchangeable.
(1) Disconnect vent hoses at air cleaner cover.
(2) Loosen clamp securing air cleaner hose to in-
take manifold. Use screwdriver to tap clamp loose.
(3) Remove air cleaner cover and hose. Then re-
move air filter from air cleaner shell (Fig. 17).
(4) Remove two bolts and one nut that secure air
cleaner housing to body panel (Fig. 17).
(5) Remove air cleaner housing from engine com-
partment.
Fig. 16 ECU Location (YJ)
Fig. 17 Air Cleaner Components
JABS OPERATION AND SERVICE 5 - 41

secondary brakeshoes move the shoes directly into
contact with the drum braking surface. The actuating
levers are interconnected by a system of cables and a
tensioner mechanism. The tensioner mechanism con-
trols parking brake adjustment.
A parking brake switch is used on all models. It is
mounted on the parking brake lever or foot pedal and
is actuated by movement of the lever/pedal. The
switch, which is in circuit with the red warning light
in the dash, will illuminate the warning light when-
ever the parking brakes are applied.
On XJ models, the cable tensioner is part of the lever
assembly. On YJ models, the tensioner and equalizer
are mounted in a bracket attached to the underbody.
On YJ models, the parking brake front cable is at-
tached to the foot pedal and cable tensioner. The ten-
sioner and rear cables are connected to the equalizer
(Fig. 1).
On XJ models, the cable tensioner is connected di-
rectly to the hand lever (a front cable is not used).
The tensioner rod is attached to the equalizer which
is the connecting point for the rear cables (Fig. 2).
The rear cables are connected to the actuating le-
ver on each secondary brakeshoe. The levers are at-
tached to the brakeshoes by a pin either pressed into,
or welded to the lever. A clip is used to secure the pin
in the brakeshoe. The pin allows each lever to pivot
independently of the brakeshoe.
Struts installed between each brakeshoe, are used to
maintain shoe alignment and equal motion when the
parking brakes are applied. Each strut is equipped with
a combination tension and anti-rattle spring.
Parking Brake Application
To apply the parking brakes, the foot pedal is
pressed downward, or the hand lever is pulled up-
ward, to an engaged position. This pulls the rear
brakeshoe actuating levers forward, by means of the
interconnected tensioner and cables.
As the actuating lever is pulled forward, the park-
ing brake strut (which is connected to both shoes),
exerts a linear force against the primary brakeshoe.
This action presses the primary shoe into contact
with the drum.
Once the primary shoe contacts the drum, force ex-
erted through the strut does not stop. Instead, fur-
ther lever movement exerts continuing force against
the strut. This force is transferred through the strut
to the secondary brakeshoe causing it to pivot into
the drum as well.
The brakeshoes remain engaged with the drum until
the levers and cables are released. A gear type ratchet-
ing mechanism is used to hold the pedal or lever in an
applied position. Parking brake release is accomplished
by means of the release handle on YJ models. Or by the
hand lever release button on XJ models.
Fig. 2 Parking Brake Components (XJ)
JPARKING BRAKES 5 - 61

(8) Install transmission. Refer to Group 21 for pro-
cedure.
CLUTCH HOUSING REPLACEMENT
The clutch housing is removable and can be re-
placed when the transmission is out of the vehicle.
The bolts attaching the housing to the transmission
case are located inside the housing (Fig. 8). Recom-
mended tightening torque for the clutch housing-to-
transmission bolts is 38 Nzm (28 ft. lbs.).
Be sure the transmission and housing mating
surfaces are clean before installing an original,
or replacement clutch housing. Dirt/foreign ma-
terial trapped between the housing and trans-
mission will cause misalignment. If
misalignment is severe enough, the result will
be clutch drag, incomplete release and hard
shifting.
CLUTCH HYDRAULIC LINKAGE REMOVAL
The clutch master cylinder, slave cylinder
and connecting line are serviced as an assem-
bly only. The linkage components cannot be
overhauled or serviced separately. The cylin-
ders and connecting line are sealed units. Also
note that removal/installation procedures forright and left hand drive models are basically
the same. Only master cylinder location is dif-
ferent.
(1) Raise vehicle.
(2) Remove fasteners attaching slave cylinder to
clutch housing.
(3) Remove slave cylinder from clutch housing (Fig.
9).
(4) Disengage clutch fluid line from body clips.
(5) Lower vehicle.
(6) Verify that cap on clutch master cylinder reser-
voir is tight. This is necessary to avoid undue spill-
age during removal.
(7) Remove clutch master cylinder attaching nuts.
Note that one nut is accessible from engine compart-
ment and one nut is accessible from under instru-
ment panel (Figs. 10 and 11).
(8) Remove clip securing clutch master cylinder
push rod to pedal and slide push rod off pedal pin.
(9) Disconnect clutch pedal position switch wires.
(10) If pedal pin is equipped with bushing, inspect
condition of bushing and replace it if worn or dam-
aged.
(11) Remove clutch hydraulic linkage through en-
gine compartment.
Fig. 8 Clutch Housing AttachmentFig. 7 Pilot Bearing Installation
JCLUTCH SERVICE 6 - 13

CLUTCH HYDRAULIC LINKAGE INSTALLATION
(1) Be sure reservoir cover on clutch master cylin-
der is tight to avoid spills.
(2) Position clutch linkage components in vehicle.
Work connecting line and slave cylinder downward
past engine and adjacent to clutch housing.
(3) Position clutch master cylinder on dash panel
(Fig. 12).
(4) Attach clutch master cylinder push rod to pin
on clutch pedal. Secure rod with new clip if neces-
sary.
(5) Install and tighten clutch master cylinder at-
taching nuts to 23-34 Nzm (200-300 in. lbs.) torque.
(6) Raise vehicle.
(7) Insert slave cylinder push rod through clutch
housing opening and into release lever. Be sure cap
on end of rod is securely engaged in lever. Check this
before installing cylinder attaching nuts.
(8) Install and tighten slave cylinder attaching
nuts to 23-34 Nzm (200-300 in. lbs.) torque.
(9) Secure clutch fluid line in body clips.
(10) Lower vehicle.
(11) Connect clutch pedal position switch wires.
CLUTCH FLUID LEVEL
The clutch fluid reservoir, master cylinder, slave
cylinder and fluid lines are prefilled with fluid at the
factory during assembly operations.
The hydraulic system should not require additional
fluid under normal circumstances. In fact,the reser-
voir fluid level will actually increase as normal
clutch wear occurs. For this reason, it is impor-
tant to avoid overfilling, or removing fluid from
the reservoir.
Fig. 9 Slave Cylinder Attachment
Fig. 10 Clutch Master Cylinder And Push Rod
Attachment (Left Hand Drive Models)
Fig. 11 Clutch Master Cylinder Location (Right Hand
Drive Models)
Fig. 12 Clutch Master Cylinder Mounting (Typical)
6 - 14 CLUTCH SERVICEJ

OVERHEAD CONSOLE
CONTENTS
page page
DIAGNOSIS............................. 2
GENERAL INFORMATION.................. 1SERVICE PROCEDURES................... 5
GENERAL INFORMATION
An overhead console featuring an electronic com-
pass and thermometer is an available option for XJ
(Cherokee) models. Following are general descrip-
tions of major components used in the overhead con-
sole. Refer to Group 8W - Wiring Diagrams for
complete circuit descriptions and diagrams.
COMPASS
The compass will display the direction in which the
vehicle is pointed using the eight major compass
headings (Examples: north is N, northeast is NE). It
does not display the headings in actual degrees. The
display is turned on or off using the COMP/TEMP
button to the left of the display.
The self-calibrating compass unit requires no ad-
justing in normal use. The only calibration that may
prove necessary is to drive the vehicle in 3 complete
circles, on level ground, in not less than 48 seconds.
This will reorient the unit to its vehicle.
The unit also will compensate for magnetism the
body of the vehicle may acquire during normal use.
However, avoid placing anything magnetic directly on
the roof of the vehicle. Magnetic mounts for an an-
tenna, a repair order hat or a funeral procession flag
can exceed the compensating ability of the compass
unit if placed on the roof panel. Magnetic bit drivers
used on the fasteners that hold the assembly to the
roof header can also affect compass operation.
If the vehicle roof should become magnetized, the
demagnetizing and calibration procedures may be re-
quired to restore proper operation.
THERMOMETER
The thermometer displays the outside ambient
temperature. The temperature displayed can be
changed from Fahrenheit to Celsius using the US/
METRIC button. The displayed temperature is not
an instant reading of conditions, but an average tem-
perature. It may take the unit several minutes to re-
act to a major temperature change such as driving
out of a heated garage into winter temperatures.
When the ignition switch is turned OFF, the lastdisplayed temperature reading stays in memory.
When the ignition switch is turned ON again, the
thermometer will display the memory temperature
for one minute; then update the display to the cur-
rent average temperature reading within five min-
utes.
READING AND COURTESY LAMPS
All reading and courtesy lamps in the overhead
console are activated by the door jamb switches.
When all doors and the liftgate are closed, the lamps
can be individually activated by depressing the corre-
sponding lens. When a door and/or the liftgate is
open, depressing the lamp lens switches will not turn
the lamps off. Refer to Group 8L - Lamps, for diag-
nosis and service of these lamps.
KEYLESS ENTRY RECEIVER
The overhead console houses the keyless entry re-
ceiver. Refer to Group 8P - Power Locks, for diagno-
sis and service of this component.
REMOTE GARAGE DOOR OPENER STORAGE
A compartment in the overhead console is designed
to hold most remote garage door opener transmitters.
The transmitter is mounted within the compartment
with an adhesive-backed hook and loop fastener
patch. Then one to three pegs are selected and
mounted on a post on the inside of the storage com-
partment door. The pegs may be stacked, if neces-
sary. The peg(s) selected must be long enough to
activate the button of the transmitter each time the
storage compartment door is depressed.
SUNGLASSES STORAGE
A flocked storage compartment for sunglasses is in-
cluded in the overhead console. This compartment
features a push/push-type latch and a viscous damp-
ening system for a fluid opening motion.
JOVERHEAD CONSOLE 8C - 1

(5) The coil ground terminal (85) is connected to
the electromagnet in the relay. Check as follows:
(a) On YJ models, it is grounded at all times.
There should be continuity to ground at cavity for
relay terminal 85 at all times. If not, repair circuit
to ground as required.
(b) On XJ models, it is energized when the head-
lamp switch is on. There should be battery voltage
at cavity for relay terminal 85 with the headlamp
switch on. If not, repair circuit to headlamp switch
as required.
ANTENNA
The following four tests are used to diagnose the
antenna with an ohmmeter:
²mast to ground test (Test 1)
²tip-of-mast to tip-of-conductor test (Test 2)
²body ground to battery ground test (Test 3)
²body ground to coaxial shield test (Test 4).
Ohmmeter test lead connections for each test are
shown in Figure 3.
TEST 1
Test 1 determines if the antenna mast is insulated
from the base. Proceed as follows:
(1) Disconnect antenna cable lead from radio chas-
sis and isolate.
(2) Connect one ohmmeter lead to tip of antenna
mast and the other lead to the antenna base. Check
for continuity.
(3) There should be no continuity. If continuity is
found, replace defective or damaged antenna base
and cable assembly.
TEST 2
Test 2 checks the antenna for an open circuit as fol-
lows:
(1) Disconnect the antenna cable lead from the ra-
dio chassis.
(2) Connect one ohmmeter test lead to tip of an-
tenna mast. Connect remaining lead to tip of an-
tenna cable lead (the part inserted into the radio).
(3) Continuity should exist (ohmmeter should only
register a fraction of an ohm). High or infinite resis-
tance indicates damage to the base and cable assem-
bly. Replace if required.
TEST 3
Test 3 checks condition of the vehicle body ground
connection as follows:
(1) Connect one ohmmeter test lead to the vehicle
fender and the other lead to the battery negative
post.
(2) Resistance should be less than one ohm.
(3) If resistance is more than one ohm, check the
braided ground strap connected to the engine and ve-
hicle body for being loose, corroded, or damaged. Re-
pair as necessary.
TEST 4
Test 4 checks condition of the ground between the
antenna base and vehicle body as follows:
(1) Connect one ohmmeter test lead to the fender
and the other lead to the crimp on the coaxial an-
tenna cable shield.
(2) Resistance should be less then one ohm.
(3) If resistance is more then one ohm:
(a) On YJ models, replace the antenna base at-
taching screws with new cadmium plated screws.
(b) On XJ models, clean and/or tighten antenna
base to fender mounting hardware.
RADIO FREQUENCY INTERFERENCE
Inspect ground connections at:
²blower motor
²electric fuel pump
²generator
²ignition module
²wiper motor
²antenna coaxial ground
²radio ground
²body-to-engine ground strap (braided).
Clean, tighten or repair as required.
Also inspect the following secondary ignition sys-
tem components:
²spark plug wire routing and condition
²distributor cap and rotor
²ignition coil
²spark plugs.
Reroute spark plug wires or replace components as
required.
Fig. 3 Antenna Tests
JAUDIO SYSTEMS 8F - 5

HORNS
CONTENTS
page page
DIAGNOSIS............................. 2
GENERAL INFORMATION.................. 1SERVICE PROCEDURES................... 3
SPECIFICATIONS......................... 5
GENERAL INFORMATION
Following are general descriptions of the major
components in the XJ (Cherokee)/YJ (Wrangler) horn
systems. Refer to Group 8W - Wiring Diagrams for
complete circuit descriptions and diagrams.
HORN SWITCH
XJ
Two horn switches are installed in the steering
wheel, one on each side of the center-mounted driv-
er's airbag module. When either switch is depressed
it completes a circuit to ground for the coil side of the
horn relay. The steering wheel and steering column
must be properly grounded for the horn switches to
function. The horn switches are only serviced as a set
with their wiring. If either switch should fail, both
switches must be replaced.
YJ
A single switch is installed in the center of the
steering wheel, directly under the horn button. When
the horn button is depressed the switch completes a
circuit to ground for the coil side of the horn relay.
The steering wheel and steering column must be
properly grounded for the horn switch to function.
The horn switch is available for service.
HORN RELAY
On XJ models, the horn relay is a mini-relay in-
stalled in the relay center, which is mounted to the
lower instrument panel reinforcement inboard of thesteering column. On YJ models, the horn relay is a
ISO relay installed in the Power Distribution Center
(PDC) near the battery tray. Refer to underside of
PDC cover for relay identification.
One side of the horn relay electromagnetic coil re-
ceives battery voltage at all times. When a horn
switch is depressed, the other side of the relay coil is
grounded. The energized relay coil causes the nor-
mally open relay contacts to close, providing battery
voltage to the horn.
If a problem is encountered with a continuously
sounding horn, it can usually be quickly resolved by
removing the horn relay until further diagnosis is
completed.
HORNS
On YJ models, a standard single, low-note, dia-
phragm-type horn is mounted and grounded to the
left inner fender shield under the hood. Dual horns
are standard equipment on XJ models. The high-note
diaphragm-type horn is mounted and grounded to
the left radiator closure panel brace behind the front
bumper. The low-note diaphragm-type horn is con-
nected in parallel with the high-note horn and is
mounted and grounded to the right radiator closure
panel brace behind the front bumper.
On XJ models, a cadmium-plated screw is
used to attach the horns to the body. Do not
substitute other types of screws as they may be-
come corroded and cause a loss of ground.
JHORNS 8G - 1