Jeep KJ Liberty Cherokee 2003 User manual

TABLE OF CONTENTS
1.0 INTRODUCTION .........................................................1
1.1 SYSTEM COVERAGE ...............................................1
1.2 SIX-STEP TROUBLESHOOTING PROCEDURE ..........................1
2.0 IDENTIFICATION OF SYSTEM .............................................1
3.0 SYSTEM DESCRIPTION AND FUNCTIONAL OPERATION ......................1
3.1 TEVES MARK 20e SYSTEM DESCRIPTION .............................1
3.1.1 PEDAL FEEL/VEHICLES CHARACTERISTICS ...................2
3.1.2 SYSTEM COMPONENTS.....................................2
3.1.3 ABS AND RED BRAKE WARNING INDICATOR...................2
3.1.4 CONTROLLER ANTILOCK BRAKE (CAB) .......................2
3.1.5 HYDRAULIC CONTROL UNIT .................................3
3.1.6 SENSORS .................................................3
3.2 ABS DIAGNOSTIC TROUBLE CODES ..................................4
3.2.1 SYSTEM INITIALIZATION.....................................4
3.2.2 DIAGNOSTIC MODE ........................................4
3.2.3 INTERMITTENT DIAGNOSTIC TROUBLE CODES ................4
3.2.4 FREEZE FRAME............................................4
3.3 USING THE DRBIIIT.................................................4
3.4 DRBIIITERROR MESSAGES .........................................4
3.4.1 DRBIIITDOES NOT POWER UP (BLANK SCREEN)...............4
3.4.2 DISPLAY IS NOT VISIBLE ....................................5
4.0 DISCLAIMERS, SAFETY, WARNINGS .......................................5
4.1 DISCLAIMERS......................................................5
4.2 SAFETY...........................................................5
4.2.1 TECHNICIAN SAFETY INFORMATION..........................5
4.2.2 VEHICLE PREPARATION FOR TESTING........................5
4.2.3 SERVICING SUB-ASSEMBLIES ...............................5
4.2.4 DRBIIITSAFETY INFORMATION...............................5
4.3 WARNING .........................................................6
4.3.1 VEHICLE DAMAGE WARNINGS ...............................6
4.3.2 ROAD TESTING A COMPLAINT VEHICLE.......................6
4.4 DIAGNOSIS................................................6
5.0 REQUIRED TOOLS AND EQUIPMENT ......................................7
6.0 GLOSSARY OF TERMS...................................................7
7.0 DIAGNOSTIC INFORMATION AND PROCEDURES ............................9
BRAKES (CAB)
BUS SYSTEM COMMUNICATION FAILURE .................................10
CAB INTERNAL FAILURE ................................................12
CLUSTER LAMP FAILURE................................................14
G-SENSOR FAILURE ....................................................16
LEFT FRONT SENSOR CIRCUIT FAILURE ..................................17
REAR SENSOR CIRCUIT FAILURE ........................................17
RIGHT FRONT SENSOR CIRCUIT FAILURE.................................17
LEFT FRONT WHEEL SPEED SIGNAL FAILURE .............................22
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TABLE OF CONTENTS - Continued
REAR WHEEL SPEED SIGNAL FAILURE ...................................22
RIGHT FRONT WHEEL SPEED SIGNAL FAILURE............................22
PUMP CIRCUIT FAILURE ................................................25
SYSTEM OVER VOLTAGE................................................29
SYSTEM UNDER VOLTAGE ..............................................32
VALVE POWER FEED FAILURE ...........................................34
*BRAKE LAMP SWITCH FAILURE .........................................37
COMMUNICATION
*NO RESPONSE FROM CONTROLLER ANTILOCK BRAKE ....................38
VERIFICATION TESTS
VERIFICATION TESTS...................................................40
8.0 COMPONENT LOCATIONS...............................................41
8.1 CONTROLLER ANTILOCK BRAKE, HYDRAULIC CONTROL UNIT, PUMP
MOTOR..........................................................41
8.2 WHEEL SPEED SENSORS ..........................................41
8.3 WHEEL SPEED SENSOR CONNECTORS..............................42
8.4 BRAKE LAMP SWITCH .............................................42
8.5 BRAKE LAMP SWITCH CONNECTOR ................................42
9.0 CONNECTOR PINOUTS .................................................43
BRAKE LAMP SWITCH ..................................................43
CONTROLLER ANTILOCK BRAKE .........................................43
DATA LINK CONNECTOR ................................................44
LEFT FRONT WHEEL SPEED SENSOR (ABS) ...............................44
PUMP MOTOR CONNECTOR .............................................44
REAR WHEEL SPEED SENSOR...........................................45
RIGHT FRONT WHEEL SPEED SENSOR (ABS)..............................45
10.0 SCHEMATIC DIAGRAMS.................................................47
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1.0 INTRODUCTION
The procedures contained in this manual include
all the specifications, instructions, and graphics
needed to diagnose the 2003 Jeep Liberty Mark 20e
Antilock Braking System (ABS) problems. The di-
agnostics in this manual are based on the failure
condition or symptom being present at time of
diagnosis.
Follow the recommendations below when choos-
ing your diagnostic path.
1. First make sure the DRBIIItis communicating
with the CAB. If the DRBIIItdisplays a ‘‘No
Response’’ condition, you must diagnose that
first.
2. Read DTC’s (diagnostic trouble codes) with the
DRBIIIt.
3. If no DTC’s are present, identify the customer
complaint.
4. Once the DTC or customer complaint is identi-
fied, locate the matching test in the Table of
Contents and begin to diagnose the symptom.
All component location views are in Section 8.0.
All connector pinouts are in Section 9.0. All sche-
matics are in Section 10.0.
An * placed before the symptom description indi-
cates a symptom with no associated DTC.
When repairs are required, refer to the appropri-
ate service manual for the proper removal and
repair procedure.
Diagnostic procedures change every year. New
diagnostic systems may be added; carryover sys-
tems may be enhanced. READ THIS MANUAL
BEFORE TRYING TO DIAGNOSE A VEHICLE
CODE. It is recommended that you review the
entire manual to become familiar with all new and
changed diagnostic procedures.
After using this book, if you have any comments
or recommendations, please fill out the form at the
back of the book and mail it back to us.
1.1 SYSTEM COVERAGE
This diagnostic manual covers the Teves Mark
20e Antilock Braking System (ABS) found on the
Jeep Liberty.
1.2 SIX-STEP TROUBLESHOOTING
PROCEDURE
Diagnosis of the antilock brake system is done in
six basic steps:
•verification of symptom
•verification of any related symptoms
•symptom analysis
•problem isolation
•repair of isolated problem
•verification of proper operation
2.0 IDENTIFICATION OF
SYSTEM
Vehicles equipped with the Teves Mark 20e an-
tilock brake system can be identified by the pres-
ence of the combined Controller Antilock Brake
(CAB) and Hydraulic Control Unit (HCU)/Pump Mo-
tor assembly mounted by the master cylinder.
3.0 SYSTEM DESCRIPTION AND
FUNCTIONAL OPERATION
3.1 TEVES MARK 20e SYSTEM
DESCRIPTION
A Controller Antilock Brake (CAB) is used to
monitor wheel speeds and to modulate (control)
hydraulic pressure in each brake channel to pre-
vent wheel lock-up during braking. The CAB also
provides a vehicle speed signal (VSS) to the Body
Control Module (BCM).
During a non-ABS stop, the system functions as a
standard front/rear split configuration. The pri-
mary supplies brake fluid pressure to the front
brakes, and the secondary supplies the rear brakes.
A conventional combination/proportioning valve is
not used. This system uses the existing ABS sole-
noids to replace and perform the same functions
that the combination and proportioning valves do.
The CAB has a special software program called
Electronic Variable Brake Proportioning (EVBP),
that monitors the wheel speeds so that when cer-
tain criteria are met the software will enable the
solenoids to perform the same brake fluid manage-
ment control as the combination/proportioning valves.
During an ABS stop, the system still uses the
front/rear hydraulic split; however, the brake sys-
tem pressure is further split into three control
channels. During ABS operation, the front wheels
are controlled independently and are on two sepa-
rate control channels. The rear wheels are con-
trolled together through one control channel. By
using separate control channels for each front
wheel, more steering control is maintained during
maximum braking.
During an antilock stop, ‘‘wheel lock-up’’ does not
necessarily mean that the wheel has locked, it
means only that the wheel is turning slower than
the vehicle speed. This is called ‘‘wheel slip’’ and is
indicated as a percentage. 0% slip means that the
wheel is rolling free and 100% slip means that the
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wheel is locked. The antilock system maintains an
average of approximately 20% wheel slip.
It is important to remember that the antilock
brake system does not shorten the vehicle stopping
distance under all driving conditions, but provides
improved control of the vehicle while stopping.
Vehicle stopping distance is still dependent on ve-
hicle speed, weight, tires, road surface, and other
factors.
3.1.1 PEDAL FEEL/VEHICLES
CHARACTERISTICS
There are several pedal feel/vehicle characteris-
tics that are considered normal for antilock braking
that may require further explanation.
When stopping conditions activate the antilock
brakes, the driver may feel some vibrations/
pulsations in the brake pedal and may hear the
solenoid valves clicking and the pump motor run-
ning. The vibrations/pulsations are caused by the
isolating, building and decaying of brake fluid pres-
sure within the brake lines. The ABS prevents
complete wheel lock-up, but some wheel slip is
required for the best braking performance. This slip
may result in some tire chirping, depending on the
road surface. The chirping should not be inter-
preted as total wheel lock-up. Total wheel lock-up
leaves black tire marks on dry pavement, antilock
braking may leave some light marks.
At the end of an ABS stop, theABS may function
all the way down to near 0 km/h (0 mph). There may
be a slight brake pedal drop anytime the ABS is
deactivated.
In case of braking on a bumpy surface, the ABS
module may activate the ABS function when it
detects wheel locking tendencies due to wheel hop.
In that event, the brake pedal may pulsate with a
perceived loss of deceleration. ABS braking may
also be activated at times while on dry pavement
with sand, gravel, or other loose debris on the road.
It should be noted that the pulsating pedal feel
characteristic will not illuminate the brake warning
lamps or set a trouble code that is stored in the
Controller Antilock Brake (CAB). When investigat-
ing a hard pedal feel, inspect the sensor and tone
wheel teeth for chips/broken teeth, damaged sensor
pole tips, excessive runout of the tone wheel, or
excessive air gap.
3.1.2 SYSTEM COMPONENTS
ANTILOCK BRAKE SYSTEM
•controller antilock brake (CAB)
•vacuum booster
•master cylinder (w/center valves)
•hydraulic control unit (HCU)
•valve block assembly: 6 valve solenoids (3 inlet
valves, 3 outlet valves)
3 accumulators
•pump/motor assembly:
1 motor
2 pumps
•internal G (acceleration) sensor
•1 internal proportioning valve
•3 wheel speed sensor/tone wheel assemblies
•ABS warning indicator
•fuses and wiring harness
3.1.3 ABS AND RED BRAKE WARNING
INDICATOR
The amber ABS warning indicator is located in
the instrument cluster. It is used to inform the
driver that the antilock function has been turned off
due to a system malfunction. On the KJ, the CAB
controls the lamp indirectly. The CAB monitors its
own functions. If the CAB determines that the ABS
indicator should be on, the CAB sends a message
via the PCI BUS to the instrument cluster and the
cluster turns on the indicator. The instrument clus-
ter sends an “are you there” message over the PCI
BUS, if the CAB does not respond the instrument
cluster will illuminate the ABS indicator.
The red brake warning indicator is located in the
instrument cluster. It can be activated by applica-
tion of the parking brake, a leak in the front or rear
wheel brake hydraulic circuit which causes the
master cylinder reservoir to be low on fluid, or by
turning the ignition switch to the start position.
The red brake warning indicator can also be turned
on if the brake fluid level switch circuit becomes
open or shorted to ground.
3.1.4 CONTROLLER ANTILOCK BRAKE
(CAB)
The antilock brake controller (CAB) is a
microprocessor-based device that monitors wheel
speeds and controls the antilock functions.
The primary functions of the CAB are:
•monitor wheel speeds
•detect wheel locking tendencies
•control fluid pressure modulations to the brakes
during antilock stop operation
•control the ABS warning indicator
•monitor the system for proper operation
•provide communication to the DRBIIItwhile in
diagnostic mode
•store diagnostic information in non-volatile mem-
ory
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The CAB continuously monitors the wheel speed
sensors. When a wheel locking tendency is detected,
the CAB will command the appropriate HCU valve
to modulate brake fluid pressure to that wheel.
Brake pedal position is maintained during an an-
tilock stop by being a closed system with the use of
3 accumulators. The CAB continues to control pres-
sure in individual hydraulic circuits until a wheel
locking tendency is no longer present. The CAB
turns on the pump/motor during an antilock stop.
The antilock brake system is constantly moni-
tored by the CAB for the proper operation. If the
CAB detects a system malfunction, it can disable
the antilock system and activate the ABS warning
indicator. If the antilock function is disabled, the
system will revert to standard base brake system
operation.
The CAB inputs include the following:
•three wheel speed sensors
•brake lamp switch
•ignition switch
•battery voltage
•diagnostic communication (PCI BUS)
•G-sensor (internal acceleration sensor)
The CAB outputs include the following:
•six valve/solenoid drivers
•pump/motor actuation
•ABS warning indicator actuation
•diagnostic communication (PCI BUS)
3.1.5 HYDRAULIC CONTROL UNIT
The hydraulic control unit (HCU) contains the
valve block assembly, and the pump/motor assem-
bly.
Valve Block Assembly: The valve block assem-
bly contains 6 valves with three inlet valves and
three outlet valves. The inlet valves are spring-
loaded in the open position and the outlet valves are
spring loaded in the closed position. During an
antilock stop, these valves are cycled to maintain
the proper slip ratio for each channel. The CAB
monitors wheel speeds. If the CAB detects a wheel
deceleration that is disproportionate to the other
wheels, it will close the inlet valve to that wheel.
This prevents any increase in fluid pressure. If the
wheel continues to decelerate disporportionately,
the CAB opens the outlet valve for that wheel to
release fluid pressure from that channel. The re-
leased fluid is routed to the accumulators. When the
wheel speed is no longer disproportionate to the
other wheels, the inlet valve will return to its
normally open position and the outlet valve will
return to the normally closed position.
Pump/Motor Assembly: The pump/motor as-
sembly provides the extra amount of fluid needed
during antilock braking. The pump is supplied fluid
that is released to the accumulators when the outlet
valve is opened during an antilock stop. The pump
is also used to drain the accumulator circuits after
the antilock stop is complete. The pump is operated
by an integral electric motor. This motor is con-
trolled by the CAB. The CAB turns on the motor
when an antilock stop is detected. The pump con-
tinues to run during the antilock stop and is turned
off approximately 3-5 seconds after the stop is
complete. The CAB monitors the pump/motor oper-
ation internally.
3.1.6 SENSORS
Wheel Speed Sensors and Tone Wheels: One
wheel speed sensor (WSS) is located at each front
wheel and another mounted to the rear axle. Each
sensor sends a small digital signal to the control
module (CAB). The CAB sends 12 volts to the
sensor. The sensor has an internal magneto resis-
tance bridge that alters the voltage and amperage
of the signal circuit. This voltage and amperage is
changed by magnetic induction when a toothed
sensor ring (tone wheel) passes by a stationary
magnetic sensor (wheel speed sensor). The CAB
measures the voltage and amperage of the digital
signals for each wheel.
The front wheel sensor is attached to the hub
housing. The tone wheel is an integral part of the
front hub. The rear speed sensor is mounted to the
axle housing. The rear tone wheel is bolted to the
ring gear inside the rear differential housing. The
wheel speed sensor air gap is NOT adjustable.
Because of internal circuitry, a resistance
check of wheel speed sensors will not deter-
mine correct or incorrect function.
Correct antilock system operation is dependent
on wheel speed signals from the wheel speed sen-
sors. The vehicle’s wheels and tires should all be the
same size and type to generate accurate signals. In
addition, the tires should be inflated to the recom-
mended pressures for optimum system operation.
Variations in wheel and tire size or significant
variations in inflation pressure can produce inaccu-
rate wheel speed signals; however, the system will
continue to function when using the mini-spare.
When driven over rough road surfaces, the rear
wheel speed sensor signals may be erratic and
cause a false trouble code.
G (Acceleration) Sensor: The CAB monitors
the acceleration sensor at all times. The sensor
assembly contains three mercury sensors that mon-
itor vehicle deceleration rates (G-force). Sudden
rapid changes in vehicle and wheel deceleration
rate trigger the sensor, sending a signal to the CAB.
The sensor assembly provides three deceleration
rates; two for forward braking and one for rearward
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braking. The G-Sensor is mounted inside the CAB
and is not separately serviceable.
3.2 ABS DIAGNOSTIC TROUBLE CODES
The Teves Mark 20e Antilock Brake System
(ABS) module may report any of the diagnostic
trouble codes (DTCs) listed in this book’s table of
contents.
Diagnostic trouble codes are retained in memory
until erased using the DRBIIIt, or automatically
erased after 255 key cycles or 3,500 miles.
3.2.1 SYSTEM INITIALIZATION
System initialization starts when the key is
turned to “RUN”. At this point, the CAB performs a
complete self-check of all electrical components in
the antilock brake systems.
At 20 km/h (12 mph) a dynamic test may be
performed. If the brake lamp switch is activated the
test will be run at 40 km/h (24 mph) regardless of
the brake lamp switch state. This will momentarily
run the pump/motor. If during the dynamic test, the
driver has his/her foot on the brake pedal, he/she
may feel the test through brake pedal pulsations.
This is a normal condition.
If any component causes a diagnostic trouble code
during system initialization or dynamic check, the
CAB will illuminate the ABS warning indicator.
3.2.2 DIAGNOSTIC MODE
For a Mark 20e system to enter a diagnostic
mode, vehicle speed must be below 10 km/h (6 mph)
and no ABS condition present. If vehicle speed is
not below 10 km/h (6 mph), a ‘‘No Response’’ mes-
sage could be displayed by the DRBIIIt. The follow-
ing are characteristics of diagnostic mode:
•The amber ABS warning indicator will blink
rapidly. If a hard trouble code is present, such as
a CAB Power Feed Circuit diagnostic trouble
code, the ABS warning indicator will be illumi-
nated without blinking until the diagnostic trou-
ble code condition is corrected.
•Antilock operation is disabled.
3.2.3 INTERMITTENT DIAGNOSTIC
TROUBLE CODES
If the malfunction is not present while perform-
ing a test procedure, the diagnostic procedures will
not locate the problem. In this case, the code can
only suggest an area to inspect. Check for the
following:
•loose or corroded conditions
•damaged components (sensors, tone wheels)
•damaged wiring
•excessive axle shaft runout
•hydraulic system leaks
•regular brake system problems, non-ABS related
If no obvious problems are found, erase diagnostic
trouble codes and with the key on, wiggle the wire
harness and connectors. Recheck for codes periodi-
cally as you work through the system. This proce-
dure may uncover a difficult to locate malfunction.
3.2.4 FREEZE FRAME
Freeze Frame takes a “snapshot” of specific vehi-
cle information the instant an ABS failure is recog-
nized and stores this information into the CAB
memory. This information can be accessed using the
DRBIIItto help diagnose the fault. Freeze Frame
will capture the first time failure or only a new
failure that occurs during the current igntion cycle.
3.3 USING THE DRBIIIT
Refer to the DRBIIItuser’s guide for instructions
and assistance with reading diagnostic trouble
codes, erasing diagnostic trouble codes and other
DRBIIItfunctions.
3.4 DRBIIITERROR MESSAGES
Under normal operation, the DRBIIItwill dis-
play one of only two error messages:
— User-Requested WARM Boot or User-
Requested COLD Boot
If the DRBIIItshould display any other error
message, record the entire display and call the
STAR Center for information and assistance. This
is a sample of such an error message display:
ver: 2.14
date: 26 Jul93
file: key_itf.cc
date: Jul 26 1993
line: 548
err: 0x1
User-Requested COLD Boot
Press MORE to switch between this display
and the application screen.
Press F4 when done noting information.
3.4.1 DRBIIITDOES NOT POWER UP
(BLANK SCREEN)
If the LED’s do not light or no sound is emitted at
start up, check for loose cable connections or a bad
cable. Check the vehicle battery voltage (data link
16-way connector cavity 16). A minimum of 11 volts
is required to adequately power the DRBIIIt. Also
check for a good ground at the DLC.
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If all connections are proper between the
DRBIIItand the vehicle or other devices, and the
vehicle battery is fully charged, an inoperative
DRBIIItmay be the result of faulty cable or vehicle
wiring.
3.4.2 DISPLAY IS NOT VISIBLE
Low temperatures will affect the visibility of the
display. Adjust the contrast to compensate for this
condition.
4.0 DISCLAIMERS, SAFETY,
WARNINGS
4.1 DISCLAIMERS
All information, illustrations, and specifications
contained in this manual are based on the latest
information available at the time of publication.
The right is reserved to make changes at any time
without notice.
4.2 SAFETY
4.2.1 TECHNICIAN SAFETY INFORMATION
WARNING: ENGINES PRODUCE CARBON
MONOXIDE THAT IS ODORLESS, CAUSES
SLOWER REACTION TIME, AND CAN LEAD
TO SERIOUS INJURY. WHEN THE ENGINE IS
OPERATING, KEEP SERVICE AREAS WELL
VENTILATED OR ATTACH THE VEHICLE
EXHAUST SYSTEM TO THE SHOP EXHAUST
REMOVAL SYSTEM.
Set the parking brake and block the wheels before
testing or repairing the vehicle. It is especially
important to block the wheels on front-wheel drive
vehicles; the parking brake does not hold the front
drive wheels.
When servicing a vehicle, always wear eye pro-
tection, and remove any metal jewelry such as
watchbands or bracelets that might make an inad-
vertent electrical contact.
When diagnosing an antilock brake problem, it is
important to follow approved procedures where
applicable. These procedures can be found in the
service manual. Following these procedures is very
important to the safety of individuals diagnostic
tests.
4.2.2 VEHICLE PREPARATION FOR
TESTING
Make sure the vehicle being tested has a fully
charged battery. If it does not, false diagnostic codes
or error messages may occur.
4.2.3 SERVICING SUB-ASSEMBLIES
Some components of the antilock brake system
are intended to be serviced in assembly only. At-
tempting to remove or repair certain sub-
components may result in personal injury and/or
improper system operation. Only those components
with approved repair and installation procedures in
the service manual should be serviced.
4.2.4 DRBIIITSAFETY INFORMATION
WARNING: EXCEEDING THE LIMITS OF THE
DRBIIITMULTIMETER IS DANGEROUS. IT
CAN EXPOSE YOU TO SERIOUS OR
POSSIBLY FATAL INJURY. CAREFULLY
READ AND UNDERSTAND THE CAUTIONS
AND THE SPECIFICATIONS LIMITS.
Follow the vehicle manufacturer’s service specifi-
cations at all times.
•Do not use the DRBIIItif it has been damaged.
•Do not use the test leads if insulation is damaged
or if metal is exposed.
•To avoid electrical shock, do not touch the test
leads, tips, or the circuit being tested.
•Choose the proper range and function for the
measurement. Do not try voltage or current mea-
surements that may exceed the rated capacity.
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Do not exceed the limits shown in the table below:
FUNCTION INPUT LIMIT
Volts 0 - 500 peak volts AC
0 - 500 volts DC
Ohms (resistance)* 0 - 1.12 megohms
Frequency Measured
Frequency Generated 0-10kHz
Temperature -58 - 1100°F
-50 - 600°C
* Ohms cannot be measured if voltage is present.
Ohms can be measured only in a non-powered
circuit.
•Voltage between any terminal and ground must
not exceed 500v DC or 500v peak AC.
•Use caution when measuring voltage above 25v
DC or 25v AC.
•Use the low current shunt to measure circuits up
to 10A. Use the high current clamp to measure
circuits exceeding 10A.
•When testing for the presence of voltage or cur-
rent, make sure the meter is functioning cor-
rectly. Take a reading of a known voltage or
current before accepting a zero reading.
•When measuring current, connect the meter in
series with test lead.
• When using the meter function, keep the DRBIIIt
away from spark plug or coil wires to avoid mea-
suring error from outside interference.
4.3 WARNING
4.3.1 VEHICLE DAMAGE WARNINGS
Before disconnecting any control module, make
sure the ignition is “off”. Failure to do so could
damage the module.
When testing voltage or continuity at any control
module, use the terminal side (not the wire end) of
the connector. Do not probe a wire through the
insulation; this will damage it and eventually cause
it to fail because of corrosion.
Be careful when performing electrical tests so as
to prevent accidental shorting of terminals. Such
mistakes can damage fuses or components. Also, a
second code could be set, making diagnosis of the
original problem more difficult.
4.3.2 ROAD TESTING A COMPLAINT
VEHICLE
Some complaints will require a test drive as part
of the repair verification procedure. The purpose of
the test drive is to try to duplicate the diagnostic
code or symptom condition.
CAUTION: Before road testing a vehicle, be
sure that all components are reassembled.
During the test drive, do not try to read the
DRBIIITscreen while in motion. Do not hang
the DRBIIITfrom the rear view mirror or
operate it yourself. Have an assistant
available to operate the DRBIIIT.
4.4 DIAGNOSIS
1. Your diagnostic test procedure must begin with a
thorough visual inspection of theABS system for
damaged components or disconnected connec-
tors. The brake lamps must be operational, and
if they are not, repair them prior to continuing.
2. Connect the DRBIIItto the data link connector
located under the dash. If the DRBIIItdoes not
power up, check the power and ground supplies
to the connector.
3. Select ‘‘Antilock Brakes’’. Turn the ignition on. If
the DRBIIItdisplays ‘‘No Response’’, refer to
Communication in the Body Diagnostic Proce-
dures manual to diagnose the symptom.
4. Read and record all ABS diagnostic trouble
codes. If the ‘‘CAB Power Feed Circuit’’ diagnos-
tic trouble code is present, it must be repaired
prior to addressing any other DTC’s. If any
additional codes are present, proceed to the
appropriate test.
5. If there are no diagnostic trouble codes present,
select ‘‘Inputs/Outputs’’ and read the brake
switch input as your press and release the brake
pedal. If the display does not match the state of
the pedal, perform the proper test. Read the
“G-Sensor” status, with the vehicle on a level
surface, both switches should read ‘‘CLOSED’’. If
the status is not correct, perform the proper test.
If a problem with the amber ‘‘ABS’’ warning
indicator exists, refer to the proper test.
6. If no other problems are found, it will be neces-
sary to road test the vehicle. THE DRBIIIt
MUST NOT BE CONNECTED TO THE
DATA LINK CONNECTOR WHEN ROAD
TESTING FOR PROPER ANTILOCK OP-
ERATION. THE SYSTEM IS DISABLED
WHILE IN DIAGNOSTIC MODE. Perform
several antilock stops from above 50 Km/h (30
mph) and then repeat steps 2, 3, and 4. If any
diagnostic trouble codes are present, proceed to
the appropriate test.
7. The following conditions should be considered
‘‘NORMAL’’ operation, and no repairs should be
attempted to correct them.
– Brake pedal feedback during an ABS stop
(clicking, vibrating)
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– Clicking, groaning or buzzing at 10 Km/h (6
mph) (drive off self test)
– Groaning noise during an ABS stop
– Slight brake pedal drop and pop noise when
ignition is initially turned on
– Brake pedal ratcheting down at the end of an
ABS stop
8. If the complaint is ABS ‘‘cycling’’ at the end of a
stop at low speeds, it may be caused by a
marginal wheel speed sensor signal. The sensor
air gap, tone wheel condition, and/or brakes
hanging up are possible causes of this condition.
9. After a road test in which no problems were
found, refer to any Technical Service Bulletins
that may apply.
5.0 REQUIRED TOOLS AND
EQUIPMENT
DRBIIIt(diagnostic read-out box)
jumper wires
ohmmeter
voltmeter
test light
6.0 GLOSSARY OF TERMS
ABS antilock brake system
BCM Body Control Module
CAB controller antilock brake
DC direct current
DLC data link connector
DRB diagnostic read-out box
EMI electro magnetic interference
EVBP Electronic Variable Brake Propor-
tioning
HCU hydraulic control unit
J/B junction block
JTEC Jeep and Truck Engine Controller
LF left front
LR left rear
PCI Programmable Communication In-
terface
PCM Powertrain Control Module
PDC power distribution center
P/M pump motor
RF right front
RR right rear
RFI radio frequency interference
SOL solenoid
WSS wheel speed sensor
7
GENERAL INFORMATION
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NOTES
8
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7.0
DIAGNOSTIC INFORMATION AND
PROCEDURES
9
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Symptom:
BUS SYSTEM COMMUNICATION FAILURE
When Monitored and Set Condition:
BUS SYSTEM COMMUNICATION FAILURE
When Monitored: Ignition on. Continuously monitors.
Set Condition: When the CAB detects a short on the PCI Bus circuit.
POSSIBLE CAUSES
INTERMITTENT CONDITION
ELECTRO-MECHANICAL INSTRUMENT CLUSTER DTC PRESENT
BUS CIRCUIT OPEN
CAB - INTERNAL FAILURE
TEST ACTION APPLICABILITY
1 Turn the ignition on.
With the DRBIIIt, read DTCs.
With the DRBIIIt, read Freeze Frame information.
With the DRBIIIt, erase DTCs.
Turn the ignition off.
Turn the ignition on.
With the DRBIIIt, read DTCs.
Does the DRBIIItdisplay BUS SYSTEM COMMUNICATION FAILURE?
All
Yes →Go To 2
No →Go To 4
2 Turn the ignition on.
With the DRBIIIt, read EMIC DTCs.
Does the DRBIIItdisplay NO ABS BUS MESSAGES RECEIVED?
All
Yes →Refer to symptom NO ABS BUS MESSAGES RECEIVED in the
BODY/INSTRUMENT CLUSTER category.
Perform ABS VERIFICATION TEST - VER 1.
No →Go To 3
3 Turn the ignition off.
Disconnect the negative (-) battery cable.
Disconnect the CAB harness connector.
NOTE: check connector - Clean/repair as necessary.
Measure the resistance of the Bus circuit between the CAB connector and the Data
Link Connector (DLC).
Is the resistance below 5.0 ohms?
All
Yes →Replace the Controller Antilock Brake in accordance with the
Service Information.
Perform ABS VERIFICATION TEST - VER 1.
No →Repair the Bus circuit for an open.
Perform ABS VERIFICATION TEST - VER 1.
10
BRAKES (CAB)
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TEST ACTION APPLICABILITY
4 Turn the ignition off.
Visually inspect the related wiring harness. Look for any chafed, pierced, pinched, or
partially broken wires.
Visually inspect the related wire harness connectors. Look for broken, bent, pushed
out, or corroded terminals.
Were any problems found?
All
Yes →Repair as necessary.
Perform ABS VERIFICATION TEST - VER 1.
No →Test Complete.
11
BRAKES (CAB)
BUS SYSTEM COMMUNICATION FAILURE — Continued
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Symptom:
CAB INTERNAL FAILURE
When Monitored and Set Condition:
CAB INTERNAL FAILURE
When Monitored: Ignition on. The CAB monitors its internal microprocessors for correct
operation.
Set Condition: If the CAB detects an internal fault, the DTC is set.
POSSIBLE CAUSES
INTERMITTENT DTC
DAMAGED CAB/CAB HARNESS CONNECTOR
CAB - GROUND CIRCUIT OPEN
ABS VALVE FUSED B(+) CIRCUIT OPEN
ABS PUMP FUSED B(+) CIRCUIT OPEN
CAB - INTERNAL FAULT
TEST ACTION APPLICABILITY
1 Turn the ignition on.
With the DRBIIIt, read DTCs.
With the DRBIIIt, erase DTCs.
Turn the ignition off.
Turn the ignition on.
With the DRBIIIt, read DTCs.
Does the DRBIIItdisplay CAB INTERNAL FAILURE?
All
Yes →Go To 2
No →Go To 6
2 Turn the ignition off.
Disconnect the CAB harness connector.
Inspect the CAB/CAB harness connector for damage.
Is ther any broken, bent, pushed out, corroded or spread terminals?
All
Yes →Repair as necessary.
Perform ABS VERIFICATION TEST - VER 1.
No →Go To 3
3 Turn the ignition off.
Disconnect the CAB harness connector.
Using a 12-volt test light connected to 12-volts, probe the CAB harness connector
ground circuits.
Did the test light illuminate?
All
Yes →Go To 4
No →Repair the CAB Ground circuit for an open.
Perform ABS VERIFICATION TEST - VER 1.
12
BRAKES (CAB)
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TEST ACTION APPLICABILITY
4 Turn the ignition off.
Using a 12-volt test light connected to ground, probe theABS Valve Fused B(+) circuit
at the CAB harness connector.
Did the test light illuminate?
All
Yes →Go To 5
No →Repair the ABS Valve Fused B(+) circuit for an open.
Perform ABS VERIFICATION TEST - VER 1.
5 Turn the ignition off.
Using a 12-volt test light connected to ground, probe the ABS Pump Fused B(+)
circuit at the CAB harness connector.
Did the test light illuminate?
All
Yes →Replace the Controller Antilock Brake in accordance with the
Service Information.
Perform ABS VERIFICATION TEST - VER 1.
No →Repair the ABS Pump Fused B(+) circuit for an open.
Perform ABS VERIFICATION TEST - VER 1.
6 Turn the ignition off.
Visually inspect the related wiring harness. Look for any chafed, pierced, pinched, or
partially broken wires.
Visually inspect the related wire harness connectors. Look for broken, bent, pushed
out, or corroded terminals.
Refer to any Hotline letters or Technical Service Bulletins that may apply.
Were any problems found?
All
Yes →Repair as necessary.
Perform ABS VERIFICATION TEST - VER 1.
No →Test Complete.
13
BRAKES (CAB)
CAB INTERNAL FAILURE — Continued
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Symptom:
CLUSTER LAMP FAILURE
When Monitored and Set Condition:
CLUSTER LAMP FAILURE
When Monitored: Ignition on. Continuous.
Set Condition: When the CAB receives a bus message from the Instrument Cluster that
the Cluster cannot illuminate the ABS Warning Indicator.
POSSIBLE CAUSES
INSTRUMENT CLUSTER OR ABS DTC PRESENT
INSTRUMENT CLUSTER
CAB--NO DTC SIGNAL TO THE INSTRUMENT CLUSTER
CAB -- PERMANENT FAULT SIGNAL
CAB--NO KEY-ON BULB CHECK SIGNAL
TEST ACTION APPLICABILITY
1 Turn the ignition on.
With the DRBIIIt, read DTCs.
Are there any Instrument Cluster or ABS DTCs present?
All
Yes →Refer to the appropriate category for the related symptom(s).
Perform ABS VERIFICATION TEST - VER 1.
No →Go To 2
2 Turn the ignition off.
Perform the Key-on Bulb Check.
Does the ABS Warning Indicator light and then go out after a few seconds?
All
Yes →Go To 3
No. Light remains after bulb check.
Replace the Controller Antilock Brake in accordance with the
Service Information.
Perform ABS VERIFICATION TEST - VER 1.
No. Indicator never comes on.
Go To 4
14
BRAKES (CAB)
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TEST ACTION APPLICABILITY
3NOTE: The DRBIIItcommunication with the CAB must be operational for
the result of this test to be valid.
Turn the ignition off.
Remove ABS Valve fuse from the PDC.
Perform the Key-on Bulb Check.
Does the ABS Indicator remain on after the bulb check?
All
Yes →Test Complete.
No →Replace the Controller Antilock Brake in accordance with the
Service Information.
Perform ABS VERIFICATION TEST - VER 1.
4NOTE: The following steps will initiate the Instrument Cluster self test.
Turn the ignition off.
Press and hold the odometer reset button.
Turn the ignition to RUN.
Observe the Instrument Cluster indicators.
Release the odometer reset button.
Did the ABS Indicator illuminate during the Instrument Cluster self test?
All
Yes →Replace the Controller Antilock Brake in accordance with the
Service Information.
Perform ABS VERIFICATION TEST - VER 1.
No →Replace the Instrument Cluster in accordance with the Service
Information.
Perform ABS VERIFICATION TEST - VER 1.
15
BRAKES (CAB)
CLUSTER LAMP FAILURE — Continued
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Symptom:
G-SENSOR FAILURE
When Monitored and Set Condition:
G-SENSOR FAILURE
When Monitored: Ignition ON. Continuously monitored when speed is greater than 2
km/h (1 mph) and there is no Brake Lamp Switch input.
Set Condition: When the CAB detects a condition outside programmed parameters from
the internal G-Sensor.
POSSIBLE CAUSES
CAB - INTERNAL FAULT
TEST ACTION APPLICABILITY
1 Turn the ignition on.
With the DRBIIIt, record and erase DTC’s.
With the DRBIIIt, read DTCs.
Does the DRBIIItdisplay G-SENSOR FAILURE?
All
Yes →Replace the Controller Antilock Brake in accordance with the
Service Information.
Perform ABS VERIFICATION TEST - VER 1.
No →Test Complete.
16
BRAKES (CAB)
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Symptom List:
LEFT FRONT SENSOR CIRCUIT FAILURE
REAR SENSOR CIRCUIT FAILURE
RIGHT FRONT SENSOR CIRCUIT FAILURE
Test Note: All symptoms listed above are diagnosed using the same tests.
The title for the tests will be LEFT FRONT SENSOR CIRCUIT
FAILURE.
When Monitored and Set Condition:
LEFT FRONT SENSOR CIRCUIT FAILURE
When Monitored: Ignition on. The CAB monitors the wheel speed circuit continuously.
Set Condition: If the CAB detects an open or shorted wheel speed sensor circuit, the
Diagnostic Trouble Code (DTC) will set.
REAR SENSOR CIRCUIT FAILURE
When Monitored: Ignition on. The CAB monitors the wheel speed circuit continuously.
Set Condition: If the CAB detects an open or shorted wheel speed sensor circuit, the
Diagnostic Trouble Code (DTC) will set.
RIGHT FRONT SENSOR CIRCUIT FAILURE
When Monitored: Ignition on. The CAB monitors the wheel speed circuit continuously.
Set Condition: If the CAB detects an open or shorted wheel speed sensor circuit, the
Diagnostic Trouble Code (DTC) will set.
POSSIBLE CAUSES
INTERMITTENT CONDITION
WHEEL SPEED SENSOR OR CONNECTOR DAMAGE
WHEEL SPEED SENSOR SIGNAL CIRCUIT FAULT
WHEEL SPEED SENSOR 12 VOLT SUPPLY CIRCUIT SHORT TO GROUND
WHEEL SPEED SENSOR 12 VOLT SUPPLY CIRCUIT OPEN
WHEEL SPEED SENSOR SIGNAL CIRCUIT SHORT TO GROUND
WHEEL SPEED SENSOR SIGNAL CIRCUIT OPEN
CAB - 12 VOLT SUPPLY CIRCUIT FAULT
CAB - SIGNAL CIRCUIT FAULT
WHEEL SPEED SENSOR 12 VOLT SUPPLY SHORT TO GROUND
WHEEL SPEED SENSOR SIGNAL CIRCUIT INOPERATIVE
17
BRAKES (CAB)
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TEST ACTION APPLICABILITY
1 Turn the ignition on.
With the DRBIIIt, read DTCs.
With the DRBIIIt, read the Freeze Frame information.
With the DRBIIIt, erase DTCs.
Turn the ignition off.
Turn the ignition on.
With the DRBIIIt, read DTCs.
NOTE: The CAB must sense all four wheels at 25km/h (15 mph) before it will
extinguish the ABS indicators.
Does the DRBIIItdisplay SENSOR CIRCUIT FAILURE?
All
Yes →Go To 2
No →Go To 13
2 Turn the ignition off.
Inspect the CAB connector, affected Wheel Speed Sensor, and affected Wheel Speed
Sensor connector.
Is the affected Wheel Speed Sensor or any of the connectors damaged?
All
Yes →Repair as necessary.
Perform ABS VERIFICATION TEST - VER 1.
No →Go To 3
3 Turn the ignition off.
Disconnect the affected Wheel Speed Sensor connector.
Note: Check connector - Clean/repair as necessary.
Turn the ignition on.
Measure the voltage between affected Wheel Speed Sensor 12 Volt Supply circuit and
ground.
Is the voltage above 10 volts?
All
Yes →Go To 6
No →Go To 4
4 Turn the ignition off.
Disconnect the CAB harness connector.
Disconnect the affected Wheel Speed Sensor connector.
Using a 12-volt test light connected to 12-volts, probe the affected Wheel Speed
Sensor 12 Volt Supply circuit.
Does the test light illuminate?
All
Yes →Repair the affected Wheel Speed Sensor 12 Volt Supply circuit for
a short to ground.
Perform ABS VERIFICATION TEST - VER 1.
No →Go To 5
18
BRAKES (CAB)
LEFT FRONT SENSOR CIRCUIT FAILURE — Continued
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