turn signal JEEP LIBERTY 2002 KJ / 1.G Workshop Manual

BRAKES - ABS
TABLE OF CONTENTS
page page
BRAKES - ABS
DESCRIPTION.........................32
OPERATION...........................32
DIAGNOSIS AND TESTING - ANTILOCK
BRAKING SYSTEM....................33
STANDARD PROCEDURE - ABS BRAKE
BLEEDING...........................33
SPECIFICATIONS.......................33
ELECTRICAL
DESCRIPTION.........................34
OPERATION...........................34FRONT WHEEL SPEED SENSOR
REMOVAL.............................34
INSTALLATION.........................34
REAR WHEEL SPEED SENSOR
REMOVAL.............................35
INSTALLATION.........................35
HCU (HYDRAULIC CONTROL UNIT)
DESCRIPTION.........................35
OPERATION...........................35
REMOVAL.............................36
INSTALLATION.........................36
BRAKES - ABS
DESCRIPTION
ANTILOCK BRAKING SYSTEM
The purpose of the antilock system is to prevent
wheel lockup during periods of high wheel slip. Pre-
venting lockup helps maintain vehicle braking action
and steering control.
The antilock CAB activates the system whenever
sensor signals indicate periods of high wheel slip.
High wheel slip can be described as the point where
wheel rotation begins approaching 20 to 30 percent of
actual vehicle speed during braking. Periods of high
wheel slip occur when brake stops involve high pedal
pressure and rate of vehicle deceleration.
Battery voltage is supplied to the CAB ignition ter-
minal when the ignition switch is turned to Run posi-
tion. The CAB performs a system initialization
procedure at this point. Initialization consists of a
static and dynamic self check of system electrical
components.
The static check occurs after the ignition switch is
turned to Run position. The dynamic check occurs
when vehicle road speed reaches approximately 30
kph (18 mph). During the dynamic check, the CAB
briefly cycles the pump and solenoids to verify oper-
ation.
If an ABS component exhibits a fault during ini-
tialization, the CAB illuminates the amber warning
light and registers a fault code in the microprocessor
memory.
ELECTRONIC BRAKE DISTRIBUTION
The electronic brake distribution (EBD) functions
like a rear proportioning valve. The EBD system usesthe ABS system to control the slip of the rear wheels
in partial braking range. The braking force of the
rear wheels is controlled electronically by using the
inlet and outlet valves located in the HCU.
OPERATION
ANTILOCK BRAKING SYSTEM
During normal braking, the master cylinder, power
booster and wheel brake units all function as they
would in a vehicle without ABS. The HCU compo-
nents are not activated.
During antilock braking fluid pressure is modu-
lated according to wheel speed, degree of slip and
rate of deceleration. A sensor at each wheel converts
wheel speed into electrical signals. These signals are
transmitted to the CAB for processing and determi-
nation of wheel slip and deceleration rate.
The ABS system has three fluid pressure control
channels. The front brakes are controlled separately
and the rear brakes in tandem. A speed sensor input
signal indicating a high slip condition activates the
CAB antilock program. Two solenoid valves are used
in each antilock control channel. The valves are all
located within the HCU valve body and work in pairs
to either increase, hold, or decrease apply pressure as
needed in the individual control channels. The sole-
noid valves are not static during antilock braking.
They are cycled continuously to modulate pressure.
Solenoid cycle time in antilock mode can be mea-
sured in milliseconds.
ELECTRONIC BRAKE DISTRIBUTION
Upon entry into EBD the inlet valve for the rear
brake circuit is switched on so that the fluid supply
from the master cylinder is shut off. In order to
decrease the rear brake pressure the outlet valve for
5 - 32 BRAKES - ABSKJ

REAR WHEEL SPEED SENSOR
REMOVAL
(1) Raise vehicle on hoist.
(2) Disconnect the sensor wire harness.
(3) Remove mounting stud from the sensor (Fig. 2).
(4) Remove sensor.
INSTALLATION
(1) Connect harness to sensor.Be sure seal is
securely in place between sensor and wiring
connector.
(2) Install O-ring on sensor (if removed).
(3) Insert sensor in differential housing.
(4) Install the sensor mounting stud and tighten to
9 N´m (80 in. lbs.).
(5) Install the sensor electical connector.
(6) Lower vehicle.
HCU (HYDRAULIC CONTROL
UNIT)
DESCRIPTION
The HCU consists of a valve body, pump motor,
and wire harness.
OPERATION
Accumulators in the valve body store extra fluid
released to the system for ABS mode operation. The
pump provides the fluid volume needed and is oper-
ated by a DC type motor. The motor is controlled by
the CAB.The valves modulate brake pressure during
antilock braking and are controlled by the CAB.
The HCU provides three channel pressure control
to the front and rear brakes. One channel controls
the rear wheel brakes in tandem. The two remaining
channels control the front wheel brakes individually.
During antilock braking, the solenoid valves are
opened and closed as needed. The valves are not
static. They are cycled rapidly and continuously to
modulate pressure and control wheel slip and decel-
eration.
During normal braking, the HCU solenoid valves
and pump are not activated. The master cylinder and
power booster operate the same as a vehicle without
an ABS brake system.
During antilock braking, solenoid valve pressure
modulation occurs in three stages, pressure increase,
pressure hold, and pressure decrease. The valves are
all contained in the valve body portion of the HCU.
PRESSURE DECREASE
The outlet valve is opened and the inlet valve is
closed during the pressure decrease cycle.
A pressure decrease cycle is initiated when speed
sensor signals indicate high wheel slip at one or
more wheels. At this point, the CAB closes the inlet
then opens the outlet valve, which also opens the
return circuit to the accumulators. Fluid pressure is
allowed to bleed off (decrease) as needed to prevent
wheel lock.
Once the period of high wheel slip has ended, the
CAB closes the outlet valve and begins a pressure
increase or hold cycle as needed.
PRESSURE HOLD
Both solenoid valves are closed in the pressure
hold cycle. Fluid apply pressure in the control chan-
nel is maintained at a constant rate. The CAB main-
tains the hold cycle until sensor inputs indicate a
pressure change is necessary.
PRESSURE INCREASE
The inlet valve is open and the outlet valve is
closed during the pressure increase cycle. The pres-
sure increase cycle is used to counteract unequal
wheel speeds. This cycle controls re-application of
fluid apply pressure due to changing road surfaces or
wheel speed.
Fig. 2 REAR WHEEL SPEED SENSOR
1 - DIFFERENTIAL HOUSING
2 - MOUNTING BOLT
3 - WHEEL SPEED SENSOR
KJBRAKES - ABS 5 - 35

The ECT sensor is a two-wire Negative Thermal
Coefficient (NTC) sensor. Meaning, as engine coolant
temperature increases, resistance (voltage) in the
sensor decreases. As temperature decreases, resis-
tance (voltage) in the sensor increases.
OPERATION
At key-on, the Powertrain Control Module (PCM)
sends out a regulated 5 volt signal to the ECT sensor.
The PCM then monitors the signal as it passes
through the ECT sensor to the sensor ground (sensor
return).
When the engine is cold, the PCM will operate in
Open Loop cycle. It will demand slightly richer air-
fuel mixtures and higher idle speeds. This is done
until normal operating temperatures are reached.
The PCM uses inputs from the ECT sensor for the
following calculations:
²for engine coolant temperature gauge operation
through CCD or PCI (J1850) communications
²Injector pulse-width
²Spark-advance curves
²ASD relay shut-down times
²Idle Air Control (IAC) motor key-on steps
²Pulse-width prime-shot during cranking
²O2 sensor closed loop times
²Purge solenoid on/off times
²EGR solenoid on/off times (if equipped)
²Leak Detection Pump operation (if equipped)
²Radiator fan relay on/off times (if equipped)
²Target idle speed
REMOVAL
2.4L
The Engine Coolant Temperature (ECT) sensor is
installed into a water jacket at left front of cylinder
head (Fig. 1).
WARNING: HOT, PRESSURIZED COOLANT CAN
CAUSE INJURY BY SCALDING. COOLING SYSTEM
MUST BE PARTIALLY DRAINED BEFORE REMOV-
ING THE COOLANT TEMPERATURE SENSOR.
(1) Partially drain cooling system.
(2) Disconnect electrical connector from sensor.
(3) Remove sensor from cylinder head.
3.7L
The Engine Coolant Temperature (ECT) sensor is
installed into a water jacket at front of intake mani-
fold near rear of generator (Fig. 2).
WARNING: HOT, PRESSURIZED COOLANT CAN
CAUSE INJURY BY SCALDING. COOLING SYSTEM
MUST BE PARTIALLY DRAINED BEFORE REMOV-
ING THE COOLANT TEMPERATURE SENSOR.(1) Partially drain cooling system.
(2) Disconnect electrical connector from sensor.
(3) Remove sensor from intake manifold.
Fig. 1 ECT AND UPPER TIMING BELT COVER/
BOLTS-2.4L
1 - UPPER TIMING BELT COVER
2 - ELECTRICAL CONNECTOR (ECT)
3 - MOUNTING BOLTS (3)
Fig. 2 MAP SENSOR / ECT SENSOR - 3.7L
1 - MOUNTING SCREWS
2 - MAP SENSOR
3 - ECT SENSOR
7 - 20 ENGINEKJ
ENGINE COOLANT TEMPERATURE SENSOR (Continued)

ENGINE COOLANT
TEMPERATURE SENSOR
DESCRIPTION
The Engine Coolant Temperature (ECT) sensor is
used to sense engine coolant temperature. The sensor
protrudes into an engine water jacket.
The ECT sensor is a two-wire Negative Thermal
Coefficient (NTC) sensor. Meaning, as engine coolant
temperature increases, resistance (voltage) in the
sensor decreases. As temperature decreases, resis-
tance (voltage) in the sensor increases.
OPERATION
At key-on, the Powertrain Control Module (PCM)
sends out a regulated 5 volt signal to the ECT sensor.
The PCM then monitors the signal as it passes
through the ECT sensor to the sensor ground (sensor
return).
When the engine is cold, the PCM will operate in
Open Loop cycle. It will demand slightly richer air-
fuel mixtures and higher idle speeds. This is done
until normal operating temperatures are reached.
The PCM uses inputs from the ECT sensor for the
following calculations:
²for engine coolant temperature gauge operation
through CCD or PCI (J1850) communications
²Injector pulse-width²Spark-advance curves
²ASD relay shut-down times
²Idle Air Control (IAC) motor key-on steps
²Pulse-width prime-shot during cranking
²O2 sensor closed loop times
²Purge solenoid on/off times
²EGR solenoid on/off times (if equipped)
²Leak Detection Pump operation (if equipped)
²Radiator fan relay on/off times (if equipped)
²Target idle speed
REMOVAL
2.4L
The Engine Coolant Temperature (ECT) sensor is
installed into a water jacket at left front of cylinder
head (Fig. 2).
WARNING: HOT, PRESSURIZED COOLANT CAN
CAUSE INJURY BY SCALDING. COOLING SYSTEM
MUST BE PARTIALLY DRAINED BEFORE REMOV-
ING THE COOLANT TEMPERATURE SENSOR.
(1) Partially drain cooling system.
(2) Disconnect electrical connector from sensor.
(3) Remove sensor from cylinder head.
3.7L
The Engine Coolant Temperature (ECT) sensor is
installed into a water jacket at front of intake mani-
fold near rear of generator (Fig. 3).
Fig. 1 ENGINE BLOCK HEATER 2.4L
1 - CORE HOLE
2 - BLOCK HEATER
3 - POWER CORD
Fig. 2 ECT AND UPPER TIMING BELT COVER/
BOLTS-2.4L
1 - UPPER TIMING BELT COVER
2 - ELECTRICAL CONNECTOR (ECT)
3 - MOUNTING BOLTS (3)
KJENGINE7s-21
ENGINE BLOCK HEATER - 2.4L (Continued)

OPERATION
The six switches in the two remote radio switch units
are normally open, resistor multiplexed momentary
switches that are hard wired to the Body Control Mod-
ule (BCM) through the clockspring. The BCM sends a
five volt reference signal to both switch units on one
circuit, and senses the status of all of the switches by
reading the voltage drop on a second circuit.
When the BCM senses an input (voltage drop) from
any one of the remote radio switches, it sends the
proper switch status messages on the Programmable
Communication Interface (PCI) data bus network to
the radio receiver. The electronic circuitry within the
radio receiver is programmed to respond to these
remote radio switch status messages by adjusting the
radio settings as requested. For diagnosis of the
BCM or the PCI data bus, the use of a DRB scan tool
and the proper Diagnostic Procedures manual are
recommended.
For more information on the features and control
functions for each of the remote radio switches, refer
to the owner's manual.
DIAGNOSIS AND TESTING - REMOTE
SWITCHES
Any diagnosis of the Audio system should
begin with the use of the DRB diagnostic tool.
For information on the use of the DRB, refer to
the appropriate Diagnostic Service Manual.
For complete circuit diagrams, refer to the appro-
priate wiring information. The wiring information
includes wiring diagrams, proper wire and connector
repair procedures, details of wire harness routing
and retention, connector pin-out information and
location views for the various wire harness connec-
tors, splices and grounds.
WARNING: DISABLE THE AIRBAG SYSTEM
BEFORE ATTEMPTING ANY STEERING WHEEL,
STEERING COLUMN, SEAT BELT TENSIONER, SIDE
AIRBAG, OR INSTRUMENT PANEL COMPONENT
DIAGNOSIS OR SERVICE. DISCONNECT AND ISO-
LATE THE BATTERY NEGATIVE (GROUND) CABLE,
THEN WAIT TWO MINUTES FOR THE AIRBAG SYS-
TEM CAPACITOR TO DISCHARGE BEFORE PER-
FORMING FURTHER DIAGNOSIS OR SERVICE. THIS
IS THE ONLY SURE WAY TO DISABLE THE AIRBAG
SYSTEM. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN ACCIDENTAL AIR-
BAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
(1) Disconnect and isolate the battery negative
cable. Remove the remote radio switch(es) (Fig. 14)
from the steering wheel (Refer to 8 - ELECTRICAL/
AUDIO/REMOTE SWITCHES - REMOVAL).(2)
Use an ohmmeter to check the switch resis-
tances as shown in the Remote Radio Switch Test
chart. If the remote radio switch resistances check OK,
go to Step 3. If not OK, replace the faulty switch.
REMOTE RADIO SWITCH TEST TABLE
Switch Switch Position Resistance
Right
(White)Volume Up 1.210 Kilohms   1%
Right
(White)Volume Down 3.010 Kilohms   1%
Right
(White)Mode Advance 0.0511 Kilohms   1%
Left
(Black)Seek Up 0.261 Kilohms   1%
Left
(Black)Seek Down 0.681 Kilohms   1%
Left
(Black)Pre-Set Station
Advance0.162 Kilohms   1%
(3) Reconnect the battery negative cable. Turn the
ignition switch to the On position. Check for 5 volts
at the radio control mux circuit cavities of the steer-
ing wheel wire harness connectors for both remote
radio switches. If OK, go to Step 4. If not OK, repair
the open or shorted radio control mux circuit to the
Body Control Module (BCM) as required.
(4) Disconnect and isolate the battery negative
cable. Disconnect the 22-way instrument panel wire
harness connector from the BCM. Check for continu-
ity between the remote radio switch ground circuit
cavities of the steering wheel wire harness connec-
tors for both remote radio switches and a good
Fig. 14 Remote Radio Switches
1 - BLACK (LEFT) SWITCH
2 - WHITE (RIGHT) SWITCH
8A - 12 AUDIOKJ
REMOTE SWITCHES (Continued)

speaker is installed on each end of the instrument
panel top pad. One 16.5 centimeter (6.5 inch) Pre-
mium woofer is located in each front door. There is
also one full-range 16.5 centimeter (6.5 inch) diame-
ter Premium full-range speaker located in each rear
door. The premium speaker system also includes a
power amplifier mounted to each front door speaker.
The total available power of the premium speaker
system is about 160 watts.
OPERATION
Two wires connected to each speaker, one feed cir-
cuit (+) and one return circuit (±), allow the audio
output signal electrical current to flow through the
voice coil. For complete circuit diagrams, refer to the
appropriate wiring information. The wiring informa-
tion includes wiring diagrams, proper wire and con-
nector repair procedures, details of wire harness
routing and retention, connector pin-out information
and location views for the various wire harness con-
nectors, splices and grounds.
REMOVAL
FRONT DOOR
(1) Disconnect and isolate the battery negative
cable.
(2) Remove the front door trim panel (Refer to 23 -
BODY/DOOR - FRONT/TRIM PANEL - REMOVAL).
(3) Remove the speaker mounting screws (Fig. 16).
(4) Remove the speaker from the door and discon-
nect the wire harness connector.
INSTRUMENT PANEL
(1) Disconnect and isolate the battery negative
cable.
(2) Remove the A-pillar trim (Refer to 23 - BODY/
INTERIOR/A-PILLAR TRIM - REMOVAL).
(3) Remove instrument panel top cover (Refer to
23 - BODY/INSTRUMENT PANEL/INSTRUMENT
PANEL TOP COVER - REMOVAL).
(4) Remove speaker mounting screws (Fig. 17).
(5) Remove speaker and disconnect the wire har-
ness connector.
Fig. 16 FRONT DOOR SPEAKER
1 - FRONT DOOR SPEAKER
2 - MOUNTING SCREW
3 - WIRE HARNESS CONNECTOR
Fig. 17 INSTRUMENT PANEL SPEAKER
1 - INSTRUMENT PANEL SPEAKER
2 - INSTRUMENT PANEL
8A - 14 AUDIOKJ
SPEAKER (Continued)

ever occurs first. The overspeed warning feature is
only enabled on a BCM that has been programmed
with a Middle East Gulf Coast Country (GCC) coun-
try code.
²No Airbag Indicator Message Warning- The
EMIC chime tone generator will generate one, short,
ªbong-likeº chime tone and turn on the ªAirbagº indi-
cator when the ignition switch is in the On position,
and a PCI data bus ªAirbagº indicator on or off mes-
sage is not received from the ACM for six consecutive
seconds.
²No Antilock Brake Indicator Message Warn-
ing- The EMIC chime tone generator will generate
one, short, ªbong-likeº chime tone and turn on the
ªABSº indicator when the ignition switch is in the On
position, and a PCI data bus ªABSº indicator on or
off message is not received from the CAB for six con-
secutive seconds.
²No Fuel Level Message Warning- The EMIC
chime tone generator will generate one, short, ªbong-
likeº chime tone and turn on the ªLow Fuelº indica-
tor when the ignition switch is in the On position,
and a PCI data bus fuel level message is not received
from the PCM for twelve consecutive seconds.
²Remote Keyless Entry Transmitter Pro-
gramming- On vehicles so equipped, the EMIC
chime tone generator will generate a single ªbong-
likeº chime tone when an electronic message is
received over the PCI data bus from the BCM indi-
cating that a Remote Keyless Entry (RKE) transmit-
ter has been successfully programmed by the
customer into the RKE module memory.
²Sentry Key Immobilizer System Transpon-
der Programming- On vehicles so equipped, the
EMIC chime tone generator will generate a single
ªbong-likeº chime tone when an electronic message is
received over PCI data bus message from the Sentry
Key Immobilizer Module (SKIM) indicating that the
Sentry Key Immobilizer System (SKIS) has been
placed in the ªCustomer Learnº programming mode,
and again each time a new SKIS transponder has
been successfully programmed by the customer.
²Turn Signal Cancel Warning- The EMIC
chime tone generator will generate repetitive ªbong-
likeº chime tones at a slow rate when the vehicle is
driven for a distance of about 3.2 kilometers (about
two miles) with a turn signal indicator flashing. The
EMIC uses an electronic message received over the
PCI data bus from the PCM, and a hard wired input
from the turn signal switch circuitry of the multi-
function switch to determine when to sound the turn
signal cancel warning. The PCM uses internal pro-
gramming and distance pulse information received
over a hard wired vehicle speed pulse input from the
BCM to determine the proper vehicle speed messages
to send to the EMIC. The BCM uses an internallyprogrammed electronic pinion factor and a hard
wired input from the rear wheel speed sensor to cal-
culate the proper distance pulse information to send
to the PCM. The electronic pinion factor represents
the proper tire size and axle ratio information for the
vehicle. These chimes will continue to sound until
the turn signal is turned Off, until the hazard warn-
ing system is turned On, or until the ignition switch
is turned to the Off position, whichever occurs first.
²Water-In-Fuel Warning- On vehicles equipped
with a diesel engine, each time the ignition switch is
turned to the On position, the EMIC chime tone gen-
erator will generate a single ªbong-likeº chime tone
the first time an electronic message is received over
the PCI data bus from the PCM requesting ªWater-
in-Fuelº indicator illumination. The PCM uses inter-
nal programming and a hard wired input from the
water-in-fuel sensor to determine the proper water-
in-fuel messages to send to the EMIC. This warning
will only occur once during an ignition cycle.
The EMIC provides chime service for all available
features in the chime warning system. The EMIC
relies upon its internal programming and hard wired
inputs from the turn signal (multi-function) switch,
the washer fluid level switch, and the engine coolant
level sensor (diesel engine only) to provide chime ser-
vice for the turn signal cancel warning, the low
washer fluid warning, and the low coolant warning
respectively. The EMIC relies upon electronic mes-
sage inputs received from other electronic modules
over the PCI data bus network to provide chime ser-
vice for all of the remaining chime warning system
features. Upon receiving the proper inputs, the EMIC
activates the integral chime tone generator to pro-
vide the audible chime warning to the vehicle opera-
tor. The internal programming of the EMIC
determines the priority of each chime request input
that is received, as well as the rate and duration of
each chime tone that is to be generated. See the own-
er's manual in the vehicle glove box for more infor-
mation on the features provided by the chime
warning system.
The hard wired chime warning system inputs to
the EMIC, as well as other hard wired circuits for
this system may be diagnosed and tested using con-
ventional diagnostic tools and procedures. However,
conventional diagnostic methods may not prove con-
clusive in the diagnosis of the EMIC, the PCI data
bus network, or the electronic message inputs used
by the EMIC to provide chime warning system ser-
vice. The most reliable, efficient, and accurate means
to diagnose the EMIC, the PCI data bus network,
and the electronic message inputs for the chime
warning system requires the use of a DRBIIItscan
tool. Refer to the appropriate diagnostic information.
KJCHIME/BUZZER 8B - 5
CHIME WARNING SYSTEM (Continued)

²RKE antenna (two circuits) - premium with
RKE only
²Tailgate ajar switch sense
²Tailgate cylinder lock switch sense
²Vehicle speed sensor
Refer to the appropriate wiring information for
additional details.
HARD WIRED OUTPUTS The hard wired outputs
of the BCM include the following:
²Courtesy lamp driver
²Courtesy lamp load shed
²Door lock relay control
²Driver door unlock relay control - premium
with RKE only
²Flip-up glass release motor driver
²Front fog lamp relay control - premium
with front fog lamps only
²Front wiper high/low relay control
²Front wiper on/off relay control
²Hazard lamp control
²High beam relay control
²Horn relay control - premium with RKE
only
²Instrument cluster wake up signal
²Low beam relay control
²Park lamp relay control
²Passenger door unlock relay control
²Rear fog lamp relay control - premium with
rear fog lamps in markets where required only
²Rear window defogger relay control
²RKE supply - premium with RKE only
²Tailgate lock driver
²Tailgate unlock driver
²Vehicle speed output
²Vehicle speed sensor supply
²VTSS indicator driver - premium with
VTSS only
Refer to the appropriate wiring information for
additional details.
GROUNDS The BCM receives ground through five
separate circuits, and also supplies a ground path to
several switches through the following hard wired
circuits:
²Ambient temperature sensor return
²Door lock switch ground
²Headlamp switch return
²Radio control mux return
²RKE ground - premium with RKE only
²Tailgate switch ground
Refer to the appropriate wiring information for
additional details.
COMMUNICATION Not including the two RKE
antenna circuits (RKE antenna + and ±), which
merely pass through the premium BCM from the
RKE module to the external RKE antenna in theinstrument panel wire harness, the BCM has the fol-
lowing communication circuits:
²PCI bus
²RKE program serial data - premium with
RKE only
²RKE transmit serial data - premium with
RKE only
Refer to the appropriate wiring information for
additional details.
MESSAGING The BCM uses the following mes-
sages received from other electronic modules over the
PCI data bus:
²Battery Temperature (PCM)
²Compass Mini-Trip Computer Button Sta-
tus (CMTC) - premium only
²Coolant Temperature (PCM)
²Distance Pulses (PCM)
²Engine Speed (PCM)
²Fuel Tank Level (PCM)
²Fuel Used (PCM)
²Intrusion Transceiver Module Commands
(ITM) - premium in markets where required
only
²Manifold Absolute Pressure (PCM)
²OK to Lock - Rolling Locks (PCM)
²SKIS Status (SKIM)
²Vehicle Identification Number (PCM)
²Vehicle Speed (PCM)
The BCM provides the following messages to other
electronic modules over the PCI data bus:
²A/C Select Switch Status (PCM)
²Country Code (EMIC, PCM, CMTC)
²Distance to Empty (CMTC) - premium only
²Door Ajar Status (EMIC)
²Exterior Lighting Status (EMIC)
²Flip-up Glass Ajar Status (EMIC)
²Fuel Economy (Average and Instantaneous)
(CMTC) - premium only
²Hood Ajar Status (ITM) - premium in mar-
kets where required only
²Ignition On Timer (CMTC) - premium only
²Intrusion Transceiver Module Commands
(ITM) - premium in markets where required
only
²Key-In Ignition Switch Status (EMIC)
²Outside Temperature (CMTC) - premium
only
²Panel Lamp Intensity (CMTC, Radio)
²Tailgate Ajar Status (EMIC)
²Radio Mode (Radio) - premium only
²Radio Preset Scan (Radio) - premium only
²Radio Seek Down (Radio) - premium only
²Radio Seek Up (Radio) - premium only
²Radio Volume Down (Radio) - premium
only
²Radio Volume Up (Radio) - premium only
8E - 6 ELECTRONIC CONTROL MODULESKJ
BODY CONTROL MODULE (Continued)

NOTE: Before replacing a Body Control Module
(BCM), use a DRBIIITscan tool to retrieve the cur-
rent settings for the BCM programmable features
and the axle ratio/tire size (electronic pinion factor).
Refer to the appropriate diagnostic information.
These settings should be duplicated in the replace-
ment BCM using the DRBIIITscan tool before
returning the vehicle to service.
(1) If the vehicle is equipped with the optional
Remote Keyless Entry (RKE) system, reinstall the
RKE module into the receptacle on the BCM. (Refer
to 8 - ELECTRICAL/POWER LOCKS/REMOTE KEY-
LESS ENTRY MODULE - INSTALLATION).
(2) Position the BCM onto the Junction Block (JB)
(Fig. 3).
(3) Install and tighten the four screws that secure
the BCM to the JB. Tighten the screws to 2 N´m (18
in. lbs.).
(4) Reinstall the Junction Block Module (JBM)
onto the instrument panel end bracket on the driver
side of the vehicle. (Refer to 8 - ELECTRICAL/
POWER DISTRIBUTION/JUNCTION BLOCK -
INSTALLATION).
(5) Reconnect the battery negative cable.
COMMUNICATION
DESCRIPTION
The DaimlerChrysler Programmable Communica-
tion Interface (PCI) data bus system is a single wire
multiplex system used for vehicle communications on
many DaimlerChrysler Corporation vehicles. Multi-
plexing is a system that enables the transmission of
several messages over a single channel or circuit. All
DaimlerChrysler vehicles use this principle for com-
munication between various microprocessor-based
electronic control modules. The PCI data bus exceeds
the Society of Automotive Engineers (SAE) J1850
Standard for Class B Multiplexing.
Many of the electronic control modules in a vehicle
require information from the same sensing device. In
the past, if information from one sensing device was
required by several controllers, a wire from each con-
troller needed to be connected in parallel to that sen-
sor. In addition, each controller utilizing analog
sensors required an Analog/Digital (A/D) converter in
order to9read9these sensor inputs. Multiplexing
reduces wire harness complexity, sensor current
loads and controller hardware because each sensing
device is connected to only one controller, which
reads and distributes the sensor information to the
other controllers over the data bus. Also, because
each controller on the data bus can access the con-
troller sensor inputs to every other controller on the
data bus, more function and feature capabilities are
possible.
In addition to reducing wire harness complexity,
component sensor current loads and controller hard-
ware, multiplexing offers a diagnostic advantage. A
multiplex system allows the information flowing
between controllers to be monitored using a diagnos-
tic scan tool. The DaimlerChrysler system allows an
electronic control module to broadcast message data
out onto the bus where all other electronic control
modules can9hear9the messages that are being sent.
When a module hears a message on the data bus
that it requires, it relays that message to its micro-
processor. Each module ignores the messages on the
data bus that are being sent to other electronic con-
trol modules.
OPERATION
Data exchange between modules is achieved by
serial transmission of encoded data over a single wire
broadcast network. The wire colors used for the PCI
data bus circuits are yellow with a violet tracer, or
violet with a yellow tracer, depending upon the appli-
cation. The PCI data bus messages are carried over
the bus in the form of Variable Pulse Width Modu-
lated (VPWM) signals. The PCI data bus speed is an
average 10.4 Kilo-bits per second (Kbps). By compar-
Fig. 3 Body Control Module Remove/Install
1 - SCREW (4)
2 - RKE MODULE
3 - BODY CONTROL MODULE
4 - JUNCTION BLOCK
8E - 8 ELECTRONIC CONTROL MODULESKJ
BODY CONTROL MODULE (Continued)

²The fuel pump is energized through the fuel
pump relay by the PCM. The fuel pump will operate
for approximately three seconds unless the engine is
operating or the starter motor is engaged.
²The O2S sensor heater element is energized via
the ASD or O2S heater relay. The O2S sensor input
is not used by the PCM to calibrate air-fuel ratio dur-
ing this mode of operation.
ENGINE START-UP MODE
This is an Open Loop mode. The following actions
occur when the starter motor is engaged.
The PCM receives inputs from:
²Battery voltage
²Engine coolant temperature sensor
²Crankshaft position sensor
²Intake manifold air temperature sensor
²Manifold absolute pressure (MAP) sensor
²Throttle position sensor (TPS)
²Camshaft position sensor signal
The PCM monitors the crankshaft position sensor.
If the PCM does not receive a crankshaft position
sensor signal within 3 seconds of cranking the
engine, it will shut down the fuel injection system.
The fuel pump is activated by the PCM through
the fuel pump relay.
Voltage is applied to the fuel injectors with the
ASD relay via the PCM. The PCM will then control
the injection sequence and injector pulse width by
turning the ground circuit to each individual injector
on and off.
The PCM determines the proper ignition timing
according to input received from the crankshaft posi-
tion sensor.
ENGINE WARM-UP MODE
This is an Open Loop mode. During engine warm-
up, the PCM receives inputs from:
²Battery voltage
²Crankshaft position sensor
²Engine coolant temperature sensor
²Intake manifold air temperature sensor
²Manifold absolute pressure (MAP) sensor
²Throttle position sensor (TPS)
²Camshaft position sensor signal
²Park/neutral switch (gear indicator signalÐauto.
trans. only)
²Air conditioning select signal (if equipped)
²Air conditioning request signal (if equipped)
Based on these inputs the following occurs:
²Voltage is applied to the fuel injectors with the
ASD relay via the PCM. The PCM will then control
the injection sequence and injector pulse width by
turning the ground circuit to each individual injector
on and off.²The PCM adjusts engine idle speed through the
idle air control (IAC) motor and adjusts ignition tim-
ing.
²The PCM operates the A/C compressor clutch
through the A/C compressor clutch relay. This is done
if A/C has been selected by the vehicle operator and
specified pressures are met at the high and low±pres-
sure A/C switches. Refer to Heating and Air Condi-
tioning for additional information.
²When engine has reached operating tempera-
ture, the PCM will begin monitoring O2S sensor
input. The system will then leave the warm-up mode
and go into closed loop operation.
IDLE MODE
When the engine is at operating temperature, this
is a Closed Loop mode. At idle speed, the PCM
receives inputs from:
²Air conditioning select signal (if equipped)
²Air conditioning request signal (if equipped)
²Battery voltage
²Crankshaft position sensor
²Engine coolant temperature sensor
²Intake manifold air temperature sensor
²Manifold absolute pressure (MAP) sensor
²Throttle position sensor (TPS)
²Camshaft position sensor signal
²Battery voltage
²Park/neutral switch (gear indicator signalÐauto.
trans. only)
²Oxygen sensors
Based on these inputs, the following occurs:
²Voltage is applied to the fuel injectors with the
ASD relay via the PCM. The PCM will then control
injection sequence and injector pulse width by turn-
ing the ground circuit to each individual injector on
and off.
²The PCM monitors the O2S sensor input and
adjusts air-fuel ratio by varying injector pulse width.
It also adjusts engine idle speed through the idle air
control (IAC) motor.
²The PCM adjusts ignition timing by increasing
and decreasing spark advance.
²The PCM operates the A/C compressor clutch
through the A/C compressor clutch relay. This is done
if A/C has been selected by the vehicle operator and
specified pressures are met at the high and low±pres-
sure A/C switches. Refer to Heating and Air Condi-
tioning for additional information.
CRUISE MODE
When the engine is at operating temperature, this
is a Closed Loop mode. At cruising speed, the PCM
receives inputs from:
²Air conditioning select signal (if equipped)
²Air conditioning request signal (if equipped)
8E - 12 ELECTRONIC CONTROL MODULESKJ
POWERTRAIN CONTROL MODULE (Continued)