1994 JEEP CHEROKEE Service Repair Manual

the sensor will not rotate, install the sensor with the
throttle shaft on the other side of the socket tangs).
The TPS will be under slight tension when rotated.
(1) Install the TPS and retaining bolts.
(2) Connect TPS electrical connector to TPS.
(3) Manually operate the throttle (by hand) to
check for any TPS binding before starting the en-
gine.
TORQUE CONVERTER CLUTCH RELAY
On YJ models, the TCC relay is located in the en-
gine compartment. It is attached to the cowl panel
with one bolt (Fig. 20). On XJ models, the TCC relay
is located in the power distribution center (PDC)
(Fig. 21). For location of this relay within the PDC,
refer to label on PDC cover.
VEHICLE SPEED SENSOR
The vehicle speed sensor (Fig. 22) is located on the
extension housing of the transmission on 2WD mod-
els. It is located on the transfer case on 4WD models.
REMOVAL
(1) Raise and support vehicle.
(2) Disconnect the electrical connector from the
sensor.
(3) Remove the sensor mounting bolt (Fig. 23).
Fig. 18 TPS LocationÐ4.0L Engine
Fig. 19 Throttle Position SensorÐInstallation
Fig. 20 TCC Relay LocationÐYJ Models
Fig. 21 Power Distribution CenterÐXJ Models
Fig. 22 Vehicle Speed Sensor LocationÐTypical
14 - 60 FUEL SYSTEMJ

(4) Remove the sensor (pull straight out) from the
speedometer pinion gear adapter (Fig. 23). Do not re-
move the gear adapter from the transmission.
INSTALLATION
(1) Clean the inside of speedometer pinion gear
adapter before installing speed sensor.
(2) Install sensor into speedometer gear adapter
and install mounting bolt.Before tightening bolt,
verify speed sensor is fully seated (mounted
flush) to speedometer pinion gear adapter.
(3) Tighten sensor mounting bolt to 2.2 Nzm (20 in.
lbs.) torque.
(4) Connect electrical connector to sensor.
Fig. 23 Sensor Removal/InstallationÐTypical
JFUEL SYSTEM 14 - 61

SPECIFICATIONS
GENERAL INFORMATION
The following specifications are published from the
latest information available at the time of publica-
tion.If anything differs between the specifica-
tions found on the Vehicle Emission Control
Information (VECI) label and the following
specifications, use specifications on VECI label.
The VECI label is located in the engine compart-
ment.
FUEL TANK CAPACITIES
FUEL SYSTEM
TORQUE
14 - 62 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

scan tool will be necessary to determine which ABS
component has malfunctioned.
ABS Light Illuminates During Brake Stop
A system fault such as loss of speed sensor signal
or solenoid failure, will cause the amber warning
light to illuminate. The most effective procedure here
is to check for obvious damage first. Then check the
electronic components with the DRB II scan tool.
BRAKE WARNING LIGHT DISPLAY
The red brake warning light and the ABS light op-
erate independently. If the red light remains on after
startup or illuminates during a brake stop, refer to
the standard brake system diagnosis section. Either
the parking brakes are applied, or a wheel brake
malfunction has occurred.
ECU DIAGNOSIS
The ECU controls all phases of antilock system op-
eration. It also differentiates between normal and an-
tilock mode braking.
The ECU monitors and processes the signals gen-
erated from all of the system sensors at all times.
The ECU program includes a self check routine
that tests each of the system components. The self
check occurs during both phases of the initialization
program. A failure of the self check program will
cause the immediate illumination of the amber warn-
ing light. The light will also illuminate if a solenoid
or other system component fails during the dynamic
phase of initialization.
If a system malfunction should occur, do not imme-
diately replace the ECU. A blown system fuse, bad
chassis ground, or loss of feed voltage will each cause
a system malfunction similar to an ECU failure.
Never replace the ECU unless diagnosis with the
DRB II scan tool indicates this is necessary.
HCU DIAGNOSIS
The HCU pump and motor and solenoid valve body
are serviced only as an assembly. The HCU assembly
should not be replaced unless a fault has actually
been confirmed. Verify fault conditions with the DRB
II scan tool before proceeding with repair.
ABS SYSTEM WIRING AND ELECTRICAL CIRCUITS
Location of the ABS fuse (in the fuse panel) is
shown in Figure 1. The engine compartment harness
routing for the ABS components is shown in Figure 2.
ABS FAULT DIAGNOSIS
The fault diagnosis chart provides additional infor-
mation on potential ABS system faults. Use the
chart as a guide when diagnosing a system problem.
Fig. 1 ABS Fuse Location
5 - 4 BRAKESJ

Fig. 2 ABS Engine Compartment Harness Routing (XJ)
JBRAKES 5 - 5