Chrysler Pacifica. Manual — part 307
1.0
INTRODUCTION
The procedures contained in this manual include
all the specifications, instructions, and graphics
needed to diagnose the Mark 25e Antilock Braking
System (ABS). The diagnostics in this manual are
based on the failure condition or symptom being
present at time of diagnosis.
Please follow the recommendations below when
choosing your diagnostic path.
1. First make sure the DRBIII
t is communicating
with the Anti-Lock Brake Module (ABM). If the
DRBIII
t displays a “No Response” condition, you
must diagnose that first.
2. Read and record DTC’s (diagnostic trouble codes)
and Freeze Frame information with the DRBIII
t.
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 asterisk (*) placed before the symptom de-
scription indicates a concern 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; carry over 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 procedure manual covers the
Teves Mark 25e Antilock Braking System (ABS)
found on the 2005 (CS) Pacifica.
1.2
SIX-STEP TROUBLESHOOTING
PROCEDURE
Diagnosis of the ABM is done in six basic steps:
•
verification of complaint
•
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 25e an-
tilock brake system can be identified by the pres-
ence of the antilock brake module with a 47-way
connector.
The presence of the Traction Control system is
indicated by the switch and bulb check.
3.0
SYSTEM DESCRIPTION AND
FUNCTIONAL OPERATION
3.1
TEVES MARK 25e SYSTEM
DESCRIPTION
The Antilock Brake Module (ABM) is used to
monitor wheel speeds and to modulate (control)
hydraulic pressure in each brake channel. The
modulated hydraulic pressure is used to prevent
wheel lock-up during braking.
The Teves Mark 25e system uses a diagonal split
hydraulic brake system. In the standard brake
mode the master cylinder primary circuit supplies
pressure to the right front and left rear wheel
brakes, and the secondary master cylinder circuit
supplies pressure to the left front and right rear
wheel brakes.
All vehicles equipped with ABS use Electronic
Variable Brake Proportioning (EVPB) to balance
front-to-rear braking when brakes are applied in
the partial braking range.
3.2
TRACTION CONTROL SYSTEM (TCS)
DESCRIPTION (IF EQUIPPED)
The main purpose of traction control is to reduce
wheel slip and maintain traction at the driven
wheels when road surfaces are slippery. The trac-
tion control system reduces wheel slip by braking
the wheel that is losing traction. The system is
designed to operate at speeds below 56 km/h (35
mph).
3.3
SYSTEM COMPONENTS
ABS
•
anti-lock brake module (ABM)
•
vacuum booster
•
master cylinder
1
GENERAL INFORMATION
•
integrated hydraulic control unit (HCU), 1 pump
motor.
•
4 wheel speed sensor/tone wheel assemblies
•
ABS warning indicator
•
fuses and wiring harness
•
fluid reservoir
•
brake lamp switch
ABS With Traction Control
•
ABM with Traction Control programming
•
HCU with four additional control valves.
•
TCS Switch
•
TCS Indicator
3.3.1
ABS AND BRAKE WARNING
INDICATORS
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. The ABS warning indicator is controlled by the
ABM. The ABM controls the lamp with a command
over the PCI bus.
The ABS Warning Indicator will remain lit during
every key cycle until a circuit or component fault is
repaired and the ABM no longer detects the fault.
After repair of a sensor signal fault or a pump motor
fault, the ABM must sense all four wheels at 25
km/h (15 mph) before it will extinguish the ABS and
TCS Indicator.
The Instrument Cluster will illuminate the ABS
Warning Indicator if it loses communication with
the ABM.
The red BRAKE warning indicator is also located
in the instrument cluster. It can be activated in
several ways. Application of the parking brake or a
low fluid signal from the fluid level switch located in
the master cylinder reservoir will cause the indica-
tor to come on.
3.3.2
ANTI-LOCK BRAKE MODULE
The ABM is a microprocessor-based device that
monitors wheel speeds and controls the antilock
functions. The ABM contains two microprocessors
that receive identical sensor signals and then inde-
pendently process the information. The results are
then compared to make sure that they agree. Oth-
erwise, the ABM will turn off the antilock and turn
on the ABS amber warning indicator.
The primary functions of the ABM are to:
•
detect wheel locking tendencies
•
control fluid pressure modulation to the brakes
during antilock stop
•
monitor the system for proper operation
•
manage traction control functions
•
provide communication to the DRBIII
t while in
diagnostic mode
•
store diagnostic information in non-volatile mem-
ory
The ABM continuously monitors the speed of
each wheel. When a wheel locking tendency is
detected, the ABM will command the appropriate
valve to modulate brake fluid pressure in its hy-
draulic unit. Brake pedal position is maintained
during an antilock stop by being a closed system.
The ABM continues to control pressure in individ-
ual hydraulic circuits until a wheel locking ten-
dency is no longer present. The ABM turns on the
pump motor during an antilock stop.
The antilock brake system is constantly moni-
tored by the ABM for proper operation. If the ABM
detects a system malfunction, it can disable the
antilock system and turn on the ABS warning
indicator. If the antilock function is disabled, the
system will revert to standard base brake system
operation.
The ABM inputs include the following:
•
diagnostic communication
•
four wheel speed sensors
•
three power feeds: valve, pump, and microproces-
sor
•
brake lamp switch
•
traction control switch
The ABM outputs include the following:
•
ABS warning indicator actuation
•
12 volts supply to wheel speed sensors
•
valve actuation
•
diagnostic communication
•
PCI bus communication
•
traction control lamp illumination
3.3.3
HYDRAULIC CONTROL UNIT
The hydraulic control unit (HCU) contains the
valve block assembly, and pump/motor assembly.
The HCU is attached to the ABM.
Valve Block Assembly: The valve block assem-
bly contains valves with four inlet valves and four
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 wheel. If a wheel detects slip, the
inlet valve is closed to prevent and further pressure
increase. Then the outlet valve is opened to release
the pressure to the accumulators until the wheel is
no longer slipping. Once the wheel is no longer
slipping, the outlet valve is closed and the inlet
valve is opened to reapply pressure. If the wheel is
decelerating
within
its
predetermined
limits
(proper slip ratio), the inlet valve will close to hold
2
GENERAL INFORMATION
the pressure constant. On vehicles which are
equipped with a traction control system, there are
four additional valves, two isolate the master cylin-
der and two shuttle. During a traction control event
the brakes are applied to reduce wheel slippage.
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 ABM. The ABM may turn on the
pump motor when an antilock stop is detected. The
pump continues to run during the antilock stop and
is turned off after the stop is complete. Under some
conditions, the pump motor will run to drain the
accumulators during the next drive off. The ABM
monitors the pump motor operation internally.
3.3.4
ABS SWITCHES/SENSORS
Master Cylinder: The master cylinder is a stan-
dard tandem compensating port design for ABS and
non ABS systems. Traction control vehicles use a
dual center port master cylinder. For proper trac-
tion control operation the standard master cylinder
must not be used.
A fluid level switch is located in the master
cylinder fluid reservoir. The switch closes when a
low fluid level is detected. The fluid level switch
turns on the brake warning indicator by grounding
the indicator circuit. This switch does not disable
the ABS system.
Wheel Speed Sensors and Tone Wheels: One
active wheel speed sensor (WSS) is located at each
wheel. The sensors use an electronic principle
known as magneto-resistive to help increase perfor-
mance, durability and low speed accuracy. The
sensors convert wheel speed into a small digital
signal. A toothed gear tone wheel serves as the
trigger mechanism for each sensor.
The ABM sends 12 volts to power an Integrated
Circuit (IC) in the sensor. The IC supplies a con-
stant 7 mA signal to the ABM. The relationship of
the tooth on the tone wheel to the permanent
magnet in the sensor, signals the IC of the sensor to
toggle a second 7 mA power supply on or off. The
output of the sensor, sent to the ABM, is a DC
voltage signal with changing voltage and current
levels. The ABM monitors the changing amperage
(digital signal) from each wheel speed sensor. The
resulting signal is interpreted by the ABM as the
wheel speed.
Because of internal circuitry, correct wheel
speed sensor function cannot be determined
by a continuity or resistance check through
the sensor.
Correct antilock system operation is dependent
on tone wheel speed signals from the wheel speed
sensors. 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
recommended pressure for optimum system opera-
tion. Variation 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 correct factory
mini-spare.
3.3.5
ABS INITIALIZATION
System initialization starts when the key is
turned to “run”. At this point, the ABM performs a
complete self-check of all electrical components in
the antilock systems.
Between 8-17 km/h (5-10 mph), a dynamic test is
performed. This will momentarily cycle the inlet
and outlet valves, check wheel speed sensor cir-
cuitry, and run the pump motor at 25 km/h (15
mph). The ABM will try to test the pump motor. If
the brake pedal is applied the test will be run at 40
km/h (24 mph) regardless of brake switch state. If,
during the dynamic test, the brake pedal is applied,
the driver may feel the test through brake pedal
pulsations. This is a normal condition.
If any component exhibits a trouble condition
during system initialization or dynamic check, the
ABM will illuminate the ABS warning indicator
and TCS Indicator, if equipped.
3.3.6
ABS DIAGNOSTIC MODE
To enter diagnostic mode, a 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” message could be dis-
played by the DRBIII
t. The following are charac-
teristics of diagnostic mode:
– The amber ABS warning indicator will blink
rapidly. If a hard trouble code, such as Battery
Voltage Out of Range code is present, the
indicator will be illuminated without blinking
until the trouble condition is cleared.
– Antilock operation is disabled.
– The HCU valves cannot be actuated when the
vehicle speed is above 8 km/h (5 mph). If valve
actuation is attempted above 8 km/h (5 mph), a
“No Response” message will be displayed on
the DRBIII
t.
3
GENERAL INFORMATION
3.3.7
TRACTION CONTROL OPERATION
(IF EQUIPPED)
The Anti-lock Brake Module (ABM) monitors
wheel speeds. If, during acceleration, the module
detects front (drive) wheel slip and the brakes are
not applied, the ABM will enter traction control
mode. Traction control works in the following order
when drive wheel slip is detected.
1. Close the (normally open) isolation valves.
2. Start pump/motor and supply volume/pressure
to front hydraulic circuits (pump runs continu-
ously during traction control).
3. Open and close build and decay valves to main-
tain minimum wheel slip and maximum trac-
tion.
The cycling of the build and decay valves is
similar to the ABS except that they work to control
wheel spin by applying brakes. ABS function is to
control wheel skid by releasing brakes.
Two pressure relief valves allow excess fluid vol-
ume to return to the reservoir when not used by the
build/decay cycles. These are required because the
pump supplies more volume than the traction con-
trol system requires.
If at any time the brake pedal is applied during a
traction control cycle, the brake lamp switch will
trigger the ABM to switch off the traction control.
The traction control system will be enabled at
each ignition cycle. It may be turned off by depress-
ing the Traction Control Switch. The traction con-
trol system function lamp will illuminate Traction
Control immediately upon depressing the traction
control switch button. The indicator will illuminate
during a traction control event.
If the ABM calculates that the brake tempera-
tures are high, the traction control system will
become inoperative until a time-out period has
elapsed. When in this thermal protection mode, the
traction control indicator will illuminate; however,
a fault will not be registered.
3.5
DIAGNOSTIC TROUBLE CODES
The Anti-lock Brake Module may report any of
several Diagnostic Trouble Codes (DTC)s. For a list
of DTC’s diagnosed in this manual, refer to the
Table of Contents.
3.6
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 ABM
memory. This information can be accessed using the
DRBIII
t to help diagnose the fault. Freeze Frame
will capture the first time failure or only a new
failure that occurs during the current ignition cycle.
3.7
DRBIII
T ERROR MESSAGES AND
BLANK SCREEN
Under normal operation, the DRBIII
t will dis-
play one of only two error messages:
– User-Requested
WARM
Boot
or
User-
Requested COLD Boot.
If the DRBIII
t should display any other error
message, record the entire display and call the
STAR Center. 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.
3.7.1
DRBIII
T DOES NOT POWER UP
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
connector cavity 16). A minimum of 11 volts is
required to adequately power the DRBIII
t.
If all connections are proper and the vehicle
battery is fully charged, an inoperative DRBIII
t
may be the result of faulty cable or vehicle wiring.
3.7.2
DISPLAY IS NOT VISIBLE
Low temperatures will affect the visibility of the
display. Adjust the contrast to compensate for this
condition.
4
GENERAL INFORMATION
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