1994 JEEP CHEROKEE brake fluid

(5) Inspect the reservoir rubber diaphragm seal for
cracks, cuts and distortion.
(6) Inspect the brake fluid tubing fittings and the
master cylinder housing for indications of fluid leak-
age. Repair as necessary.
(7) Install the brake fluid reservoir cover.
ANTI-LOCK BRAKE SYSTEMÐXJ VEHICLES
The anti-lock brake system fluid reservoir for XJ
Vehicles is located in the engine compartment at the
left side of the dash panel.
(1) Turn the ignition switch ON and allow the
pump motor to operate until it automatically de-en-
ergizes.
(2) Clean the cover before removing it.
CAUTION: Over-filling could cause fluid overflow
and possible reservoir damage when the pump mo-
tor energizes.
(3) The brake fluid level should be no lower than
the MIN arrow indicator on the side of the reservoir
(Fig. 8). If not, add brake fluid as necessary. Raise
the fluid level to the MAX arrow indicator only. Do
not over-fill the reservoir.
(4) Turn the ignition switch OFF.
BRAKE SYSTEM INSPECTION
BRAKE FLUID HOSES/TUBING
(1) Inspect all brake fluid rubber hoses (Fig. 9) for
cracks, swelling, kinks, a distorted condition and
fluid leakage.
(2) Inspect the brake fluid hoses and tubing that
are routed along the frame rail.
PADS/LININGS, ADJUSTER, WHEEL CYLINDERS AND
CALIPER
The front disk brake pads can be visually inspected
via the brake caliper inspection ports.(1) Inspect the brake pads and linings for excessive
wear, cracks, charred surfaces and broken rivets.
(2) Inspect the brake pads and linings for contam-
ination with brake fluid, axle lubricant and/or an-
other fluid.
(3) Replace the brake pads and/or linings if they
are worn to within 0.78 mm (1/32 in) of the rivet
head.
(4) Operate the rear brake self-adjuster lever and
pivot. Test the operation of the self-adjuster screw for
ease of movement.
(5) Inspect the self-adjuster components for bent
areas, frayed cables, loose or overheated springs, and
a binding condition.
Fig. 7 Reservoir Fluid LevelÐTypicalFig. 8 Reservoir Fluid LevelÐAnti-Lock Brake
System
Fig. 9 Rubber Brake Fluid HoseÐTypical
JLUBRICATION AND MAINTENANCE 0 - 33

(6) Inspect the disc brake caliper dust boot for cor-
rect installation, damage/tears and indications of
brake fluid leakage. Inspect the bushings and pins
for corrosion, tears and a binding condition.
(7) Pull the rear wheel cylinder dust boot back to
expose the wheel cylinder housing and inspect for
fluid leaks. Inspect the pistons and cylinder bores for
proper appearance.
(8) Inspect the brake differential warning valve
and housing for indications of leakage, kinked hoses
and loose fittings.
PARK BRAKE
(1) As applicable, engage the park brake lever or
pedal and then release it.
(2) If the park brake is functioning normally, test
it for smooth operation and vehicle-holding capabil-
ity.
(3) Inspect the park brake cables for kinks, fraying
and a binding condition.
(4) With the park brake released, the rear wheels
should rotate without restriction. Adjust the park
brake cable tension at the equalizer (Fig. 10), if nec-
essary.
(5) Repair any park brake malfunctions.
BRAKE OPERATIONAL TEST
(1) Drive the vehicle and test for proper brake ac-
tion.
(2) Note any indication of drum/rotor overheating,
wheel dragging or the vehicle pulling to one side
when the brakes are applied.
(3) Evaluate any performance complaints received
from the owner/operator.
(4) Repair the brake system as necessary (refer to
Group 5ÐBrakes for additional information and ser-
vice procedures).
TIRES
RECOMMENDED MAINTENANCE
The general condition of the tires and the inflation
pressures should be inspected at the same time the
engine oil is changed and the oil filter is replaced.
In addition, the tires/wheels should be rotated pe-
riodically to ensure even tread wear and maximum
tread life. The tires/wheels should be rotated initially
after the first 12 000-km (7,500-miles). Thereafter,
after each 24 000-km (15,000-miles) interval of vehi-
cle operation has elapsed.
INSPECTION
Inspect the tires for excessive wear, damage, etc.
Test the tires for the recommended inflation pres-
sure. Refer to the tire inflation pressure decal located
on the inside of the glove box door, and also to Group
22ÐTires And Wheels.
ROTATION
Refer to Group 22ÐTires And Wheels for the rec-
ommended method of tire/wheel rotation for a Jeept
vehicle.
BODY COMPONENTS
RECOMMENDED MAINTENANCE
Body components should be lubricated (as required)
after each 48 000-km (30,000-miles) interval of vehi-
cle operation has elapsed.
LUBRICANT SPECIFICATIONS
All applicable exterior and interior body compo-
nents should be:
²inspected for excessive wear,
²cleaned, and
²all pivot/sliding contact areas of the components
should be lubricated with the specified lubricant.
Refer to the Body Lubricant Specifications chart
below. When excessive wear is apparent, replace/re-
pair as necessary.
LUBRICATION
All pivoting and sliding contact areas, including:
²seat tracks,
²door hinges/latches/strikers, and
²liftgate/tailgate/hood hinges (Fig. 11),
should be lubricated periodically to ensure quiet,
easy operation and to protect against wear and cor-
rosion.
(1) As required, lubricate the body components
with the specified lubricants.
(2) When lubricating door weatherstrip seals, ap-
ply the lubricant to a cloth and wipe it on the seal.
(3) Prior to the application of lubricant, the compo-
nent should be wiped clean to remove dust, grit and
debris. After lubrication, any excess lubricant should
be removed.
Fig. 10 Park Brake Equalizer (XJ)ÐTypical
0 - 34 LUBRICATION AND MAINTENANCEJ

MODEL 30 AXLE AND TUBE AXLE (2WD)
INDEX
page page
Axle Bushing Replacement................. 32
Axle Shaft Ð Cardan U-Joint................ 25
Axle Specifications....................... 46
Backlash and Contact Pattern Analysis........ 44
Cleaning/Inspection....................... 35
Differential and Pinion Measurement.......... 38
Differential Assembly...................... 36
Differential Disassembly.................... 34
Differential Installation..................... 43
Differential Removal...................... 32
Differential Shim Pack Measurement and Adjustment.42
Drive Axle Assembly ReplacementÐXJ Vehicles . 21
Drive Axle Assembly ReplacementÐYJ Vehicles . 21Final Assembly.......................... 44
Hub Bearing and Axle Shaft................ 24
Information............................. 20
Inner Axle Shaft Oil Seal Replacement........ 33
Lubricant Change........................ 22
Lubricant Specifications.................... 20
Pinion Gear Assembly/Installation............ 40
Pinion Gear Depth Information.............. 37
Pinion Removal/Disassembly................ 34
Pinion Seal Replacement.................. 23
Steering Knuckle and Ball Studs............. 30
Vacuum Disconnect Axle Ð YJ Vehicles....... 26
INFORMATION
The housing for Model 30 front axles consists of an
iron center casting (differential housing) with axle
shaft tubes extending from either side. The tubes are
pressed into and welded to the differential housing to
form a one-piece axle housing.
The integral type housing, hypoid gear design has
the centerline of the pinion set above the centerline
of the ring gear.
The axle has a fitting for a vent hose used to re-
lieve internal pressure caused by lubricant vaporiza-
tion and internal expansion.
The axles are equipped with semi-floating axle
shafts, meaning that loads are supported by the hub
bearings. The axle shafts are retained by nuts at the
hub bearings. The hub bearings are bolted to the
steering knuckle at the outboard end of the axle tube
yoke. The hub bearings are serviced as an assembly.
The axles are equipped with ABS brake sensors.
The sensors are attached to the knuckle assemblies
and tone rings are pressed on the axle shaft.Use
care when removing axle shafts as NOT to dam-
age the tone wheel or the sensor.
The stamped steel cover provides a means for in-
spection and servicing the differential.
The Model 30 axle has the assembly part number
and gear ratio listed on a tag. The tag is attached to
the housing cover. Build date identification codes are
stamped on the axle shaft tube cover side.
The differential case is a one-piece design. The dif-
ferential pinion mate shaft is retained with a roll
pin. Differential bearing preload and ring gear back-
lash is adjusted by the use of shims (select thick-
ness). The shims are located between the differential
bearing cones and case. Pinion bearing preload is set
and maintained by the use of collapsible spacer.
PINION GEAR DEPTH MEASUREMENT WITH
PINION GAUGE SET 6774, Pinion Block 6733 and
Dial Indicator C-3339 is performed when;²Axle/differential housing is being replaced
²Original pinion depth shim pack is lost or mis-
placed
²Replacing the differential case
²Original differential bearing shim pack is lost or
misplaced
COMMAND-TRACÐYJ VEHICLES
The Command-Trac system is a vacuum disconnect
axle. The system has a two-piece axle shaft coupled
together by a shift collar. For two-wheel drive oper-
ation, the vacuum motor and shift fork disengages
the axle shaft splines. For four-wheel drive opera-
tion, the vacuum motor and shift fork engages the
splines.
SELEC-TRACÐXJ VEHICLES
The Selec-Trac system is a non-disconnect axle.
Shifting from two-wheel to four-wheel drive is at the
transfer case.
For XJ vehicles equipped withSelec-Tracand
ABS brake system, refer to Group 5ÐBrakes for ad-
ditional service information.
LUBRICANT SPECIFICATIONS
Multi-purpose, hypoid gear lubricant should be
used for Model 30 axles. The lubricant should have
MIL-L-2105C and API GL 5 quality specifications.
MOPARtHypoid Gear Lubricant conforms to both of
these specifications.
²The factory fill for the Model 30 axle is SAE 75W
gear lubricant.Do not use heavier weight lubri-
cant, this will cause axle engagement difficulties.
²The factory installed lubricant quantity for the
NON-DISCONNECT TYPE AXLE is 5061 fluid oz..
²The factory installed lubricant quantity for the
VACUUM-DISCONNECT TYPE AXLE is 5661 fluid
oz..
2 - 20 FRONT SUSPENSION AND AXLEJ

Refer to Group 0, Lubrication and Maintenance for
additional information regarding temperature range,
viscosity and fluid level.
CAUTION: If the axle is submerged in water, the lu-
bricant must be replaced immediately to avoid the
possibility of premature axle failure.
DRIVE AXLE ASSEMBLY REPLACEMENTÐXJ
VEHICLES
REMOVAL
(1) Raise the vehicle and position support stands
under the frame rails slightly in behind the lower
suspension arm frame brackets.
(2) Remove the front wheels.
(3) Remove the brake components and ABS brake
sensor (if equipped). Refer to Group 5ÐBrakes.
(4) On 4WD vehicles, disconnect the axle vent
hose.
(5) On 4WD vehicles, mark the drive shaft yoke
and axle pinion yoke for alignment reference. Discon-
nect the drive shaft from the axle.
(6) Disconnect the stabilizer bar link at the axle
bracket.
(7) Disconnect the shock absorbers from axle
bracket.
(8) Disconnect the track bar from the axle bracket.
(9) Disconnect the tie rod and drag link from the
steering knuckle. Disconnect the steering dampener
from the axle bracket.
(10) Support the axle with a hydraulic jack under
the differential.
(11) Disconnect the upper and lower suspension
arms from the axle bracket.
(12) Lower the jack enough to remove the axle.
The coil springs will drop with the axle.
(13) Remove the coil springs from the axle bracket.
INSTALLATION
CAUTION: All suspension components that use rub-
ber bushings should be tightened with the vehicle
at the ride height. It is important to have the
springs supporting the weight of the vehicle when
the fasteners are torqued. If the springs are not at
their normal ride position, vehicle ride comfort
could be affected along with premature rubber
bushing wear. Rubber bushings must never be lu-
bricated.
(1) Install the springs and retainer clip. Tighten
the retainer bolts to 21 Nzm (16 ft. lbs.) torque.
(2) Support the axle on a hydraulic jack under the
differential. Position the axle under the vehicle.
(3) Raise the axle with a floor jack and align it
with the spring pads.(4) Position the upper and lower suspension arm at
the axle bracket. Install bolts and nuts finger
tighten.
(5) Connect the track bar to the axle bracket and
install the bolt.Do not tighten at this time.
It is important that the springs support the
weight of the vehicle when the track bar is con-
nected. If the springs are not at their usual po-
sition, the vehicle ride comfort could be affected.
(6) Install the shock absorber and tighten the bolt
to 19 Nzm (14 ft. lbs.) torque.
(7) Install the stabilizer bar link to the axle
bracket. Tighten the nut to 95 Nzm (70 ft. lbs.)
torque.
(8) Install the drag link and tie rod to the steering
knuckles and tighten the nuts to 47 Nzm (35 ft. lbs.)
torque. Install the steering dampener to the axle
bracket and tighten the nut to 75 Nzm (55 ft. lbs.)
torque.
(9) Install the brake components and ABS brake
sensor (if equipped). Refer to Group 5ÐBrakes.
(10) On 4WD vehicles, connect the vent hose to the
tube fitting.
(11) On 4WD vehicles, align the reference marks
and connect the drive shaft to the axle yoke. Tighten
the U-joint clamp bolts to 19 Nzm (14 ft. lbs.) torque.
(12) Check differential lubricant and add if neces-
sary.
(13) Install the wheel and tire assemblies.
(14) Remove the supports and lower the vehicle.
(15) Tighten the upper suspension arm nuts to 75
Nzm (55 ft. lbs.) torque. Tighten the lower suspension
arm nuts to 115 Nzm (85 ft. lbs.) torque.
(16) Tighten the track bar bolt at the axle bracket
to 100 Nzm (74 ft. lbs.) torque.
(17) Check the front wheel alignment.
DRIVE AXLE ASSEMBLY REPLACEMENTÐYJ
VEHICLES
REMOVAL
(1) Raise the vehicle and position support stands
under the frame rails slightly behind the spring
frame brackets.
(2) Remove the front wheels.
(3) Remove the brake components and ABS brake
sensor (if equipped). Refer to Group 5ÐBrakes.
(4) Disconnect the axle vent hose and axle shift
motor vacuum harness.
(5) Mark the drive shaft yoke and axle pinion yoke
for alignment reference. Disconnect the drive shaft
from the axle.
(6) Disconnect the stabilizer bar link at the axle
bracket.
(7) Disconnect the shock absorbers from axle
bracket.
(8) Disconnect the track bar from the axle bracket.
JFRONT SUSPENSION AND AXLE 2 - 21

charges when the PCM supplies a ground. By switch-
ing the ground path on and off, the PCM regulates
ignition timing.
The sensors and switches that provide inputs to the
powertrain control module (PCM) comprise the En-
gine Control System. It is also comprised of the PCM
Outputs (engine control devices that the are operated
by the PCM).
SYSTEM DIAGNOSIS
The powertrain control module (PCM) tests many
of its own input and output circuits. If a Diagnostic
Trouble Code (DTC) is found in a major system, this
information is stored in the PCM memory. Refer to
On-Board Diagnostics in the MFI SystemÐGeneral
Diagnosis section of this group for DTC information.
POWERTRAIN CONTROL MODULE (PCM)
The PCM operates the fuel system. The PCM was
formerly referred to as the SBEC or engine control-
ler. The PCM is a pre-programmed, dual micropro-
cessor digital computer. It regulates ignition timing,
air-fuel ratio, emission control devices, charging sys-
tem, speed control, air conditioning compressor
clutch engagement and idle speed. The PCM can
adapt its programming to meet changing operating
conditions.
On XJ models, the PCM is located in the engine
compartment next to the air cleaner (Fig. 1). On YJ
models, the PCM is located in the engine compart-
ment behind the windshield washer fluid reservoir
(Fig. 2).
The PCM receives input signals from various
switches and sensors. Based on these inputs, the
PCM regulates various engine and vehicle operations
through different system components. These compo-
nents are referred to as PCM Outputs. The sensors
and switches that provide inputs to the PCM are con-
sidered PCM Inputs.The PCM adjusts ignition timing based upon in-
puts it receives from sensors that react to: engine
rpm, manifold absolute pressure, coolant tempera-
ture, throttle position, transmission gear selection
(automatic transmission), vehicle speed and the
brake switch.
The PCM adjusts idle speed based on inputs it re-
ceives from sensors that react to: throttle position,
vehicle speed, transmission gear selection, coolant
temperature and from inputs it receives from the air
conditioning clutch switch and brake switch.
Based on inputs that it receives, the PCM adjusts
ignition coil dwell. The PCM also adjusts the gener-
ator charge rate through control of the generator
field and provides speed control operation.
Powertrain Control Module (PCM) Inputs:
²Generator output
²A/C request (if equipped with factory A/C)
²A/C select (if equipped with factory A/C)
²Auto shut down (ASD) sense
²Intake air temperature sensor
²Battery voltage
²Brake switch
²Engine coolant temperature sensor
²Crankshaft position sensor
²Ignition circuit sense (ignition switch in run posi-
tion)
²Manifold absolute pressure sensor
²Overdrive/override switch
²Oxygen sensor
²Park/neutral switch (auto. trans. only)
²SCI receive (DRB scan tool connection)
²Speed control resume switch
²Speed control set switch
²Speed control on/off switch
²Camshaft position sensor signal
²Throttle position sensor
²Vehicle speed sensor
²Sensor return
²Power ground
Fig. 1 PCM LocationÐXJ Models
Fig. 2 PCM LocationÐYJ Models
14 - 18 FUEL SYSTEMJ

BRAKES
CONTENTS
page page
ABS BRAKE DIAGNOSIS.................. 3
ABS COMPONENT SERVICE.............. 47
ABS SYSTEM OPERATION............... 39
ANTILOCK BRAKE SYSTEM OPERATION.... 43
BRAKE BLEEDINGÐBRAKE FLUID AND
LEVELÐBRAKELINES AND HOSES....... 13
BRAKE PEDAL AND BRAKELIGHT SWITCH . . 65
DISC BRAKES.......................... 24DRUM BRAKES........................ 34
GENERAL INFORMATION.................. 1
PARKING BRAKES...................... 56
POWER BRAKE BOOSTER................ 22
SERVICE BRAKE DIAGNOSIS.............. 7
SPECIFICATIONS....................... 67
STANDARD MASTER CYLINDER........... 20
GENERAL INFORMATION
INDEX
page page
Antilock Brake System (ABS)................ 1
Brake Fluid/Lubricants/Cleaning Solvents........ 1
Brake Safety Precautions................... 2
Brake Warning Lights...................... 1
Brakelining Material........................ 1Hydraulic Components..................... 1
Jeep Body Code Letters.................... 2
Power Brakes............................ 1
Wheel Brake Components................... 1
WHEEL BRAKE COMPONENTS
Front disc and rear drum brakes are used on all
models. The disc brake components consist of single
piston calipers and ventilated rotors. The rear drum
brakes are dual shoe, units with cast brake drums.
The parking brake mechanism is lever and cable
operated. The cables are attached to actuating levers
mounted on the rear drum brake secondary shoes.
The parking brake mechanism is operated by a foot
pedal on YJ models and a hand lever on XJ models.
POWER BRAKES
Power brakes are standard on all models. A vac-
uum operated power booster is used for standard and
ABS brake applications.
HYDRAULIC COMPONENTS
A dual reservoir master cylinder is used for all
standard brake applications. A combination propor-
tioning valve/pressure differential switch is used. A
center feed style master cylinder is used for ABS
brake applications.
BRAKELINING MATERIAL
The factory installed brakelining on all models con-
sists of an organic base material combined with me-
tallic particles. The lining does not contain asbestos.
BRAKE WARNING LIGHTS
A red, brake warning light is used to alert the
driver if a pressure differential exists between the
front and rear hydraulic systems. The light also
alerts the driver when the parking brakes are ap-
plied. The light illuminates for a few seconds at start
up as part of a bulb check procedure.
An additional warning light is used on models with
antilock brakes. This light is amber in color and is
located in the same side of the instrument cluster as
the red warning light. The amber light illuminates
only when an ABS system fault occurs.
ANTILOCK BRAKE SYSTEM (ABS)
An antilock brake system (ABS) is available on
XJ/YJ models. The system is an electronically oper-
ated, all-wheel brake control system. The ABS sys-
tem is designed to retard wheel lockup during
periods of high wheel slip braking. Refer to the anti-
lock brake section for operation and service informa-
tion.
BRAKE FLUID/LUBRICANTS/CLEANING SOLVENTS
Recommended fluid for all Jeep vehicles is Mopar
DOT 3 brake fluid, or an equivalent meeting SAE
J1703 and DOT 3 standards.
JBRAKES 5 - 1

Use Mopar Multi Mileage grease to lubricate drum
brake pivot pins and rear brakeshoe contact points
on the support plates. Use GE 661, or Dow 111 sili-
cone grease on caliper bushings and mounting bolts.
Use fresh brake fluid or Mopar brake cleaner to
clean or flush brake system components. These are
the only cleaning materials recommended.
CAUTION: Never use gasoline, kerosene, methyl or
isopropyl alcohol, paint thinner, or any fluid con-
taining mineral oil to clean the system components.
These fluids damage rubber cups and seals. If sys-
tem contamination is suspected, check the fluid for
dirt, discoloration, or separation into distinct layers.
Drain and flush the system with new brake fluid if
contamination is suspected.
JEEP BODY CODE LETTERS
The body/model identification code letters for Jeep
vehicles are as follows:
²Code letters XJ: Cherokee
²Code letters YJ: Wrangler/YJ
The code letters are used throughout this group to
simplify model identification and component applica-
tion.
BRAKE SAFETY PRECAUTIONS
WARNING: ALTHOUGH FACTORY INSTALLED
BRAKELINING ON JEEP VEHICLES IS MADE FROM
ASBESTOS FREE MATERIALS, SOME AFTER MARKET
BRAKELINING MAY CONTAIN ASBESTOS. THIS
SHOULD BE TAKEN INTO ACCOUNT WHEN REPAIR-
ING A VEHICLE WITH PRIOR BRAKE SERVICE. WEAR
A RESPIRATOR WHEN CLEANING BRAKE COMPO-
NENTS AS ASBESTOS FIBERS CAN BE A HEALTH
HAZARD. NEVER CLEAN WHEEL BRAKE COMPO-
NENTS WITH COMPRESSED AIR. USE A VACUUM
CLEANER SPECIFICALLY DESIGNED FOR REMOVING
BRAKE DUST. IF A VACUUM CLEANER IS NOT AVAIL-
ABLE, CLEAN THE PARTS WITH WATER DAMPENED
SHOP RAGS. DO NOT CREATE DUST BY SANDING
BRAKELINING. DISPOSE OF ALL DUST AND DIRT
SUSPECTED OF CONTAINING ASBESTOS FIBERS IN
SEALED BAGS OR CONTAINERS. FOLLOW ALL REC-
OMMENDED SAFETY PRACTICES PRESCRIBED BY
THE OCCUPATIONAL SAFETY AND HEALTH ADMINIS-
TRATION (OSHA) AND THE ENVIRONMENTAL PRO-
TECTION AGENCY (EPA), FOR HANDLING AND
DISPOSAL OF PRODUCTS CONTAINING ASBESTOS.
5 - 2 BRAKESJ

ABS BRAKE DIAGNOSIS
INDEX
page page
ABS Fault Diagnosis....................... 4
ABS System Wiring and Electrical Circuits...... 4
ABS Warning Light Display.................. 3
Brake Warning Light Display................. 4
Diagnosis Procedures...................... 3
ECU Diagnosis........................... 4
HCU Diagnosis........................... 4Loss of Sensor Input....................... 3
Operating Sound Levels.................... 3
Rear Speed Sensor Air Gap................. 3
Steering Response........................ 3
Vehicle Response in Antilock Mode............ 3
Wheel/Tire Size and Input Signals............. 3
DIAGNOSIS PROCEDURES
ABS diagnosis involves three basic steps. First is
observation of the warning light display. Second is a
visual examination for low fluid level, leaks, parking
brakes applied, or obvious damage to system compo-
nents or wires. The third step involves using the
DRB II scan tool to identify a faulty component.
The visual examination requires a check of reser-
voir fluid level and all system components. Things to
look for are leaks, loose connections, or obvious com-
ponent damage.
The final diagnosis step involves using the DRB II
scan tool to determine the specific circuit or compo-
nent at fault. The tester is connected to the ABS di-
agnostic connector in the passenger compartment.
The connector is at the driver side of the center con-
sole under the instrument panel. Refer to the DRB II
scan tool Manual for tester procedures. Also refer to
the ABS Fault Diagnosis charts at the end of this
section for additional diagnosis information.
Initial faults should be cleared and the vehicle road
tested to reset any faults that remain in the system.
Faults can be cleared with the DRB II scan tool.
REAR SPEED SENSOR AIR GAP
The front wheel sensors are fixed and cannot be ad-
justed. Only the rear sensor air gap is adjustable. Air
gap must be set with a brass feeler gauge.
Correct air gap is important to proper signal gen-
eration. An air gap that is too large may cause com-
plete loss of sensor input. Or, a gap that is too small
could produce a false input signal, or damaging con-
tact between the sensor and tone ring.
WHEEL/TIRE SIZE AND INPUT SIGNALS
Antilock system operation is dependant on accurate
signals from the wheel speed sensors. Ideally, the ve-
hicle wheels and tires should all be the same size
and type. However, the Jeep ABS system is designed
to function with a compact spare tire installed.
OPERATING SOUND LEVELS
The ABS pump and solenoid valves may produce
some sound as they cycle on and off. This is a normal
condition and should not be mistaken for faulty oper-
ation.
VEHICLE RESPONSE IN ANTILOCK MODE
During antilock braking, the HCU solenoid valves
cycle rapidly in response to ECU inputs.
The driver will experience a pulsing sensation
within the vehicle as the solenoids decrease, hold, or
increase pressure as needed. A pulsing brake pedal
will also be noted.
The pulsing sensation occurs as the solenoids cycle
during antilock mode braking. A slight pulse in the
brake pedal may also be noted during the dynamic
self check part of system initialization.
STEERING RESPONSE
A modest amount of steering input is required dur-
ing extremely high deceleration braking, or when
braking on differing traction surfaces. An example of
differing traction surfaces would be when the left
side wheels are on ice and the right side wheels are
on dry pavement.
LOSS OF SENSOR INPUT
Sensor malfunctions will most likely be due to
loose connections, damaged sensor wires, incorrect
rear sensor air gap, or a malfunctioning sensor. Ad-
ditional causes of sensor faults would be sensor and
tone ring misalignment or damage.
ABS WARNING LIGHT DISPLAY
ABS Light Illuminates At Startup
The amber ABS light illuminates at startup as
part of the system self check feature. The light illu-
minates for 2-3 seconds then goes off as part of the
normal self check routine.
ABS Light Remains On After Startup
An ABS system fault is indicated when the light
remains on after startup. Diagnosis with the DRB II
JBRAKES 5 - 3