Chrysler Town, Dodge Caravan. Manual — part 694
NOTE: For 2003 model year, some vehicles
will
integrate
the
Transmission
Control
Module and Powertrain Control Module into a
single control module. This new module is
the
Next
Generation
Controller
for
DaimlerChrysler and will be referred to as the
Powertrain
Control
Module
(PCM).
The
Transmission Control Module is part of the
Powertrain Control Module.
New Diagnostic procedures and New DTC
numbers are some of the changes you will
see which reflect the new combined module
technology. The PCM will have four color
coded connectors C1 through C4, (C1-BLK,
C2-GRAY, C3-WHITE, C4-GREEN), each PCM
connector will have 38 pins each. Two new
tools are used for probing and repairing the
New PCM connectors. A New tool to release
the pins from the PCM connectors Miller
#3638 is introduced, you must use the Miller
tool #3638 to release the connector pins or
harness and connector damage will occur.
Also a New tool for probing connectors Miller
#8815 is introduced, you must use the Miller
tool #8815 to probe the PCM pins or harness
and connector damage will occur. There is
also a new Verification test and module
replacment procedure for the PCM.
3.6
DOOR AJAR SYSTEM
The door ajar and liftgate ajar states are used as
inputs for the Body Control Module (BCM). The
BCM uses these inputs to determine exactly what
position the doors and liftgate are in. The DRBIII
t
will display the state of the door ajar and the
liftgate ajar switches in Inputs/Outputs. It’s impor-
tant to note, that when any door, or the liftgate is
closed, the switch state on the DRBIII
t will show
OPEN. When any door, or the liftgate is open the
switch state on the DRBIII
t will show CLOSED.
During diagnosis, if a door or the liftgate is closed
and the DRBIII
t displays the switch state as
CLOSED, it indicates a shorted ajar circuit. If the
door or the liftgate is open and the DRBIII
t dis-
plays the switch state as OPEN, it indicates an
open ajar circuit.
12
GENERAL INFORMATION
3.7
EXTERIOR LIGHTING SYSTEM
3.7.1
HEADLAMP POWER
The Headlamp Switch is a direct input to the
BCM. The BCM sends a BUS message to the FCM
informing it of a headlamp switch status change.
The FCM then turns on power to the headlamps
through four “fuseless” circuits. These circuits are
electronically controlled and continuously moni-
tored for malfunctions. Power is supplied to each
filament in a separate circuit. For vehicles equipped
with daytime running Lamps (DRL), the FCM elec-
tronically steps down the headlamp voltage to pro-
vide the desired illumination.
3.7.2
HEADLAMP SWITCH
The Headlamp Switch uses a multiplexed (MUX)
circuit to the Body Control Module (BCM). The
Headlamp Switch controls the Fog lamp relay, Park
lamps and the Low and High headlamps. The BCM
then sends a signal through the PCI Bus line to the
FCM as to what state the switch has selected. The
FCM energizes the high side output drivers to turn
ON the desired lamps.
3.7.3
PARK LAMP RELAY
The Park Lamp Switch is a direct input to the
BCM. The BCM sends a BUS message to the FCM
informing it to turn on the park lamp relay. The
park lamp relay is then powered through low side
control of the FCM. This circuit is electronically
controlled and continuously monitored for malfunc-
tions.
3.7.4
FOG LAMP RELAY
The Fog Lamp switch is a direct input to the
BCM. The BCM sends a BUS message to the FCM
informing it to turn on the fog lamp relay. The fog
lamp relay is then powered through low side control
of the FCM. This circuit is electronically controlled
and continuously monitored for malfunctions. Fog
lamp functionality is not equipped on all vehicles.
The FCM “learns” that the vehicle is equipped with
fog lamps by reading the BCM BUS message.
3.7.5
FOG LAMPS
The BCM controls the operation of the fog lamp
relay that turns the fog lamps ON and OFF. The
Fog lamps can only be ON when the park and low
beams are ON. If the high beams are switched ON
then the Fog lamps will be automatically turned
OFF.
3.7.6
EXTERIOR LIGHTING BATTERY
SAVER
The BCM monitors the status of, and controls, the
Park Lamps, Headlamps and Fog Lamp relays. If
any exterior lamps are left ON after the ignition is
turned OFF, the BCM will turn them OFF after 3
minutes.
3.7.7
AUTO HEADLAMPS
This feature is available on vehicles equipped
with both the Electrocromatic Mirror (ECM) and
the Compass/Mini-Trip Computer (CMTC). When
the BCM detects a day/night signal from the CMTC,
an ECM is present and Auto Headlamp mode is
selected.
3.8
FRONT CONTROL MODULE
The Front Control Module (FCM) is an electrical
control and interface center located in the engine
compartment. When it is mated to the Power Dis-
tribution Center (PDC), it is referred to as the
Integrated Power Module (IPM). The IPM, with its
fuses and relays provides power and signal distri-
bution throughout most of the vehicle. The FCM
receives both hard wire and digital electronic inputs
from the vehicle electrical system through the PDC.
Based on these inputs and the ignition switch
position, it provides direct power feeds and relay
control to some of the vehicles’ most critical electri-
cal systems.
The Front Control Module provides the following
features:
Controlled power feeds:
•
Front airbag system
•
Side airbag system
•
Headlamp power
•
EATX module power (4 speed only)
•
Front washer motor
•
Rear washer motor
•
Cabin Heater
•
Brake shift interlock system
Relay controls:
•
Fog lamp relay (when equipped)
•
Park lamp relay
•
Front wiper on relay
•
Front wiper high/low relay
•
Accessory relay
•
Horn relay
•
Front & rear blower relay
•
Name brand speakers (NBS) relay
13
GENERAL INFORMATION
•
Electronic back light (EBL) run only relay
Electrical inputs:
•
Headlamp battery supplies 1 & 2
•
Module battery supply
•
Power ground
•
Ignition switch RUN or START position status
•
Ignition switch START only status
•
PCI Bus
•
Stop lamp switch
•
Horn switch
•
Back-up switch
•
Wiper park switch
•
Washer fluid level switch
•
Brake fluid level switch
•
Ambient temperature sensor
•
Right park lamp outage
•
Left park lamp outage
•
Battery IOD
•
Battery (+) connection detection
•
Flash reprogramming voltage
3.8.1
CONTROLLED POWER FEEDS
Front airbag system
The FCM provides power to the Occupant Re-
straint Control (ORC) system through two “fuse-
less” circuits (ORC RUN/START, and ORC RUN
only). These circuits are electronically controlled
and continuously monitored for malfunctions.
Power is supplied while the ignition switch is in the
RUN and START positions on pin 48 of the FCM
connector, and in the RUN only position on pin 29.
Side airbag system
The FCM provides power to the Side Impact
Airbag Control Module (SIACM) system through
one “fuseless” circuit. This circuit is electronically
controlled and continuously monitored for malfunc-
tions. Power is supplied in the ignition RUN and
START positions on pin 28 of the FCM connector.
Headlamp power
The headlamp switch is a direct input to the
BCM. The BCM sends a PCI Bus message to the
FCM informing it of a headlamp switch status
change. The FCM then turns on power to the
headlamps through four “fuseless” circuits. These
circuits are electronically controlled and continu-
ously monitored for malfunctions. Power is supplied
to each filament in a separate circuit (RH low on pin
6, RH high on pin 4, LH low on pin 3 and LH high
on pin 5). For vehicles equipped with Daytime
Running Lamps (DRL), the FCM electronically
steps down the headlamp voltage to provide the
desired illumination.
EATX power
The electronic automatic 4 speed transmission
module is powered when the ignition switch is in
the UNLOCK, RUN or START positions. This cir-
cuit is electronically controlled and continuously
monitored for malfunctions. Power is supplied
through pin 27 of the FCM connector.
Front washer motor
The front washer switch is a direct input to the
BCM. The BCM sends a PCI Bus message to the
FCM informing it of a request to wash. The front
washer motor is then powered through low side
control inside the FCM. This circuit is electronically
controlled and continuously monitored for malfunc-
tions. In addition, the FCM electronically protects
the washer motor from system voltages higher than
16 volts by automatically switching off the low side
circuit. The low side circuit is connected to pin 45 in
the FCM connector.
Rear washer motor
The rear washer switch is a direct input to the
BCM. The BCM sends a PCI Bus message to the
FCM informing it of a request to wash. The rear
washer motor is then powered through low side
control inside the FCM. This circuit is electronically
controlled and continuously monitored for malfunc-
tions. In addition, the FCM electronically protects
the washer motor from system voltages higher than
16 volts by automatically switching off the low side
circuit. The low side circuit is connected to pin 46 in
the FCM connector.
Cabin Heater
When the ignition is in Run, the FCM monitors
the PCI bus for the Cabin Heater Activation re-
quest. The Automatic or Manual Temperature Con-
trol initiates this request only when all conditions
for the Cabin Heater activation are favorable. The
request carries the status bit that the FCM requires
to activate its Cabin Heater Assist Control output.
This output is a low side driver (coming from FCM
pin 15) which supplies a ground signal to the Cabin
Heater (pin 5). When the Cabin Heater receives this
ground signal input, it interprets this as an activa-
tion signal. The FCM low side driver is also capable
of diagnostic sensing. The driver will sense an open
circuit when the driver is off, and will sense a short
to voltage when the driver is on. The FCM will set
DTCs for both of these types of faults. For addi-
tional information, refer to Cabin Heater under
General Information and Diagnostic Procedures in
the manual.
Brake shift interlock system
The brake shift interlock solenoid receives power
from both high side and low side controls inside the
FCM. The high side control is on the same circuit as
the EATX module power, and the low side control
14
GENERAL INFORMATION
comes through pin 47 of the FCM connector. The
solenoid is controlled by the low side driver when
the brake pedal is pressed. Both circuits are contin-
uously monitored for malfunctions.
3.8.2
RELAY CONTROLS
Fog lamp relay
The fog lamp switch is a direct input to the BCM.
The BCM sends a PCI Bus message to the FCM
informing it to turn on the fog lamp relay. The fog
lamp relay is then powered through low side control
on pin 33 of the FCM. This circuit is electronically
controlled and continuously monitored for malfunc-
tions. Fog lamp functionality is not equipped on all
vehicles. The FCM “learns” that the vehicle is
equipped with fog lamps by reading the BCM PCI
Bus message.
Park lamp relay
The park lamp switch is a direct input to the
BCM. The BCM sends a PCI Bus message to the
FCM informing it to turn on the park lamp relay.
The park lamp relay is then powered through low
side control on pin 13 of the FCM. This circuit is
electronically controlled and continuously moni-
tored for malfunctions.
Front wiper on relay
The front wiper switch is a direct input to the
BCM. The BCM sends a PCI Bus message to the
FCM informing it to turn on the front wiper on
relay. The front wiper on relay is then powered
through low side control on pin 14 of the FCM. This
circuit is electronically controlled and continuously
monitored for malfunctions.
Front wiper high/low relay
The front wiper switch is a direct input to the
BCM. The BCM sends a PCI Bus message to the
FCM informing it to turn on the front wiper high/
low relay. The relay switches power between the low
speed and high speed windings of the wiper motor.
The front wiper high/low relay is powered through
low side control on pin 34 of the FCM. This circuit is
electronically controlled and continuously moni-
tored for malfunctions.
Accessory relay
The accessory relay works in conjunction with the
FCM’s power accessory delay feature to control the
operation of the radio, power windows, washer
motors, wiper motors and power outlet. The acces-
sory relay is turned on through low side control on
pin 35 of the FCM. This circuit is electronically
controlled and continuously monitored for malfunc-
tions. Depending on the ignition switch position,
the accessory relay will remain on or will time-out
and turn off. The accessory relay remains on in the
RUN and ACCY positions of the ignition switch. In
the UNLK and OFF positions, the relay will remain
energized for 45 seconds then turn off. During this
time-out period, if the driver or passenger doors are
opened, the relay will turn off immediately. While
the ignition switch is in the START position, the
relay will also drop-out, then resume operation.
Accessory relay operation is most noticeable by
observing the operation of the radio or blower
functions.
Horn relay
The horn relay operates through a direct wire
input to the FCM from the horn switch (FCM pin
17) , or a PCI Bus message from the BCM. The relay
responds to the horn switch, remote door lock and
VTA alarm functions. The horn relay is powered
through low side control on pin 10 of the FCM.
Under normal operating conditions, if the horn is
pressed for longer than 30 seconds, the FCM will
automatically deactivate the horn to prevent dam-
age to it. The FCM will re-activate control of the
relay after a 25 second cool-down period. This
circuit is electronically controlled and continuously
monitored for malfunctions.
Front and rear blower relay
The blower control switch is part of the Automatic
Temperature Control (ATC) or A/C-Heater Control
Module, (Manual Temp). When the blower switch is
turned on, the ATC or A/C-Heater Control Module
sends a PCI Bus message to the FCM. The front and
rear blower relay is then powered through low side
control on pin 30 of the FCM. The relay provides the
high side to the blower motor, and the blower speed
is governed through low side control in the ATC or
A/C-Heater Control Module. This circuit is electron-
ically controlled and continuously monitored for
malfunctions.
Name Brand Speakers (NBS) relay
The NBS relay operates through the vehicle bus
interface between the radio and the FCM. When the
radio is turned on, the radio sends a PCI Bus
message to the FCM. The NBS relay is then pow-
ered on through low side control on pin 11 of the
FCM. The relay supplies power to the amplified
speaker, and ground is supplied through the radio.
This circuit is electronically controlled and contin-
uously monitored for malfunctions.
Electronic Back Light (EBL) relay
The rear defrost switch is part of the Automatic
Temperature Control or A/C-Heater Control Module
(Manual Temp). When the ignition switch is in the
RUN position and the rear defrost switch is turned
on, the ATC or A/C-Heater Control Module sends a
PCI Bus message to the FCM. The EBL run only
relay is then powered through low side control on
pin 31 of the FCM. The relay provides the high side
to the rear window defrost grid, and ground is
attached to the vehicle body. The FCM will only
15
GENERAL INFORMATION
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