2001 CHRYSLER VOYAGER Door

3.5 COMMUNICATION
The Programmable Communication Interface or
PCI Bus is a single wire multiplexed network capa-
ble of supporting binary encoded messages shared
between multiple modules. The PCI bus circuit is
identified as D25 and is white with a violet tracer.
Additional tracer colors may be added to the violet
in order to distinguish between different module
connections. The modules are wired in parallel.
Connections are made in the harness using splices.
One splice called the Diagnostic Junction Port,
serves as the ªHubº of the bus. The Diagnostic
Junction Port provides an access point to isolate
most of the modules on the bus in order to assist in
diagnosing the circuit. The following modules are
used on the RG:
²Body Control Module
²Front Control Module
²Occupant Restraint Controller
²Left Side Impact Airbag Control Module
²Right Side Impact Airbag Control Module
²Controller Antilock Brake
²Powertrain Control Module
²Engine Control Module - Diesel Only
²Radio
²CD Changer
²Transmission Control Module
²Automatic Temperature Control Module
²A/C Heater Control Module (MTC)
²Sentry Key Immobilizer Module
²RKE/Thatcham Alarm Module
²Memory Seat/Mirror Module
²Overhead Console
²Mechanical Instrument Cluster
²Left Sliding Door Control Module
²Right Sliding Door Control Module
²Power Liftgate Module
Each module provides its own bias and termina-
tion in order to transmit and receive messages. The
bus voltage is at zero volts when no modules are
transmitting and is pulled up to about seven and a
half volts when modules are transmitting.
The bus messages are transmitted at a rate
averaging 10800 bits per second. Since there is only
voltage present when the modules transmit and the
message length is only about 500 milliseconds, it is
ineffective to try and measure the bus activity witha conventional voltmeter. The preferred method is
to use the DRBIIItlab scope. The 12v square wave
selection on the 20-volt scale provides a good view of
the bus activity. Voltage on the bus should pulse
between zero and about seven and a half volts.
Refer to the following figure for some typical dis-
plays.
The PCI Bus failure modes are broken down into
two categories. Complete PCI Bus Communication
Failure and individual module no response. Causes
of complete PCI Bus Communication Failure in-
clude a short to ground or battery on the PCI
circuit. Individual module no response can be
caused by an open circuit at either the Diagnostic
Junction Port or the module, or an open battery or
ground circuit to the affected module.
Symptoms of a complete PCI Bus Communication
Failure would include but are not limited to:
²All gauges on the MIC stay at zero
²All telltales on MIC illuminate
²MIC backlighting at full intensity
²Dashed lines in the overhead console ambient
temperature display
²No response received from any module on the PCI
bus (except the PCM)
²No start (if equipped with Sentry Key Immobi-
lizer)
Symptoms of Individual module failure could
include any one or more of the above. The difference
would be that at least one or more modules would
respond to the DRBIIIt.
Diagnosis starts with symptom identification. If a
complete PCI Bus Communication Failure is sus-
pected, begin by identifying which modules the
vehicle is equipped with and then attempt to get a
response from the modules with the DRBIIIt.Ifany
modules are responding, the failure is not related to
the total bus, but can be caused by one or more
modules PCI circuit or power supply and ground
circuits. The DRBIIItmay display ªBUS +/- SIG-
NAL OPENº or ªNO RESPONSEº to indicate a
communication problem. These same messages will
be displayed if the vehicle is not equipped with that
particular module. The CCD error message is a
default message used by the DRBIIItand in no way
indicates whether or not the PCI bus is operational.
The message is only an indication that a module is
either not responding or the vehicle is not equipped.
11
GENERAL INFORMATION

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 DRBIIIt
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 DRBIIItwill show
OPEN. When any door, or the liftgate is open the
switch state on the DRBIIItwill show CLOSED.
During diagnosis, if a door or the liftgate is closed
and the DRBIIItdisplays the switch state as
CLOSED, it indicates a shorted ajar circuit. If the
door or the liftgate is open and the DRBIIItdis-
plays the switch state as OPEN, it indicates an
open ajar circuit.
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 ªfuselessº 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 inform-
ing 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 ªlearnsº 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.
12
GENERAL INFORMATION

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.
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
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 ªlearnsº 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 lowside 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.
14
GENERAL INFORMATION

± Evap Temp Sensor Shorted
± Evap Temp Sensor Open
± A/C Pressure Too Low
± A/C Pressure Too High
± Invalid Conditions for Cooldown Test, Evap
Temperature Too Low
If a message other than Cooldown Test Passed
occurs, refer to the appropriate symptom for diag-
nosis.
3.9.1.7 ACTIVE AND STORED TROUBLE
CODES
The Automatic Temperature Control (ATC) is
capable of storing Active and Stored trouble codes.
Active codes indicate a current fault in the system.
Stored codes indicate that a problem has occurred
in the system, however is not currently present.
Active codes cannot be erased until the problem
causing the code has been repaired. At this time the
Active code is converted to a Stored code, which can
be erased using the DRBIIIt.
3.9.2 MANUAL TEMPERATURE CONTROL
3.9.2.1 SYSTEM AVAILABILITY
Depending on the model, either a Single-Zone Air
Conditioning System or a Dual-Zone Air Condition-
ing System is currently available in these vehicles.
3.9.2.2 CABIN HEATER
For Vehicles equipped with a diesel engine, a
Cabin Heater is used in conjunction with the HVAC
system. The Cabin Heater is designed to supply the
vehicle's occupants with heat prior to the engine
reaching operating temperature. For additional in-
formation on this system, refer to Cabin Heater
under General Information and Diagnostic Proce-
dures in this manual.
3.9.2.3 ZONE CONTROL ± SINGLE-ZONE
The Single-Zone Air Conditioning System main-
tains incoming air temperature, airflow, fan speed,
and fresh air intake for the entire vehicle from the
instrument panel mounted A/C ± Heater Control
Module. The full range of temperature that the
system can produce in any mode for the entire
vehicle is available by positioning the blend control
to the desired range.
3.9.2.4 ZONE CONTROL ± DUAL-ZONE
The Dual-Zone Air Conditioning System main-
tains incoming air temperature, airflow, fan speed,
and fresh air intake for the entire vehicle from the
instrument panel mounted A/C ± Heater ControlModule. In addition, this system provides com-
pletely independent side-to-side control of incoming
air temperature. The full range of temperature that
the system can produce in any mode is available on
either side of the vehicle by positioning the inde-
pendent driver and passenger blend controls to the
desired range.
3.9.2.5 AIR DISTRIBUTION
The HVAC unit has five fully adjustable instru-
ment panel outlets. Side-window demister outlets
in the instrument panel eliminate door ducts and
door-to-instrument panel seals. A single, central
mounted outlet delivers air for defrosting the wind-
shield. Air exhausters allow air entering at the
front of the vehicle to flow out the back to the rear
occupants. Mid-cabin comfort control directs only
cooling air flow to the intermediate seat occupants
through outlets at the rear of each front door trim
panel. Air is supplied to these outlets from the
instrument panel through ducts in the doors that
use molded seals at the instrument panel to prevent
air leakage. Wide outlets under the front seats with
directional dividers distribute heated air across the
floor to the intermediate seat occupants. Ducts in
the center of the vehicle under the carpet deliver air
from the HVAC unit to these outlets. Models
equipped with Dual-Zone A/C systems also include
a dust and odor air filter installed in the HAVC
housing.
3.9.2.6 DOOR ACTUATORS
The electric door actuators are a two-wire design.
Each door actuator uses a similar connector wired
directly to the A/C ± Heater Control Module. Single-
Zone systems have one blend door actuator, one
mode door actuator, and one recirculation door
actuator. Dual-Zone systems have two blend door
actuators, one mode door actuator, and one recircu-
lation door actuator. All of the door actuators are
accessible from the vehicle's interior.
3.9.2.7 DOOR ACTUATOR CONTROL
The A/C ± Heater Control Module knows the
number of operating actuator revolutions required
for full door travel as well as the number of actuator
commutator pulses per revolution. Using these pa-
rameters, the A/C ± Heater Control Module runs
the actuator for the number of commutator pulses
that correspond to the desired door position. To
maintain accuracy, the system recalibrates itself
periodically at known zero and full travel condi-
tions.
17
GENERAL INFORMATION

3.9.2.8 HVAC SYSTEM RELAYS
The Integrated Power Module (IPM) houses and
provides power to the A/C Clutch Relay and Front
Blower Motor Relay.
3.9.2.9 EVAPORATOR TEMPERATURE
SENSOR
An evaporator temperature sensor, located on the
A/C expansion valve under the hood, replaces the
previously used fin sensor.
3.9.2.10 A/C ± HEATER CONTROL
MODULE, SWITCH OPERATION
Power Switch
The Power Switch is a momentary contact switch.
The switch LED illuminates when the switch is on.
The Power Switch setting is remembered during
power down.
Rear Window Defogger Switch
The Rear Window Defogger Switch is a momen-
tary contact switch. Toggling the switch results in
the A/C ± Heater Control Module sending a change
of state message to the FCM to provide rear window
defogger activation or deactivation respectively.
The switch LED illuminates when the switch is on.
Recirculation Switch
The Recirculation Switch is a momentary contact
switch. Toggling the switch on results in the A/C ±
Heater Control Module signaling the actuator to
close the fresh-air door. Toggling the switch off
results in the A/C ± Heater Control Module signal-
ing the actuator to open the fresh-air door. The
switch LED illuminates when the switch is on.
When the Power Switch is off, the A/C ± Heater
Control Module closes the fresh-air door to prevent
outside air from entering the passenger compart-
ment. The recirculation mode will cancel whenever
defrost is requested. Pressing the Recirculation
Switch while in defrost mode will illuminate the
Recirculation Switch LED, but only while the but-
ton is pressed. Under this circumstance, the recir-
culation request will be denied and the fresh-air
door will remain in the fresh position. All door
positions are determined relative to the number of
commutator pulses required to provide full travel of
the door. On command, the A/C ± Heater Control
Module runs the actuator for the number of pulses
corresponding to the desired door position.
A/C Switch
The A/C Switch is a momentary contact switch.
Toggling the switch results in the A/C ± Heater
Control Module sending a change of state message
to the Powertrain Control Module (PCM ± gasoline)or Engine Control Module (ECM ± diesel) to provide
A/C compressor clutch activation or deactivation
respectively. The A/C ± Heater Control Module will
only provide this request if EVAP function is found
acceptable. The Power Switch must be on to make
the A/C switch active. The switch LED illuminates
when the switch is on. The A/C Switch setting is
remembered during power down.
Blower Switch
The rotary Blower Switch has five positions, Low,
M1, M2, M3, and High. The Power Switch must be
on to make the Blower Switch active. Toggling the
Power Switch results in the A/C ± Heater Control
Module sending a request to the FCM to provide
blower motor activation or deactivation respec-
tively.
Blend Switch ± Single Zone
The single rotary Blend Switch has multiple
detents to control the full range of temperature that
the system can produce in any mode. Rotating the
switch results in the A/C ± Heater Control Module
signaling the actuator to move the blend door. All
door positions are determined relative to the num-
ber of commutator pulses required to provide full
travel of the door. On command, the A/C ± Heater
Control Module runs the actuator for the number of
pulses corresponding to the desired door position.
Blend Switch ± Dual Zone
The dual sliding Blend Switches have multiple
detents to control the full range of temperature that
the system can produce an any mode. The upper
slide pot controls the driver-side blend door, while
the lower slide pot controls the passenger-side
blend door. Sliding the switch results in the A/C ±
Heater Control Module signaling the actuator to
move the blend door. All door positions are deter-
mined relative to the number of commutator pulses
required to provide full travel of the door. On
command, the A/C ± Heater Control Module runs
the actuator for the number of pulses corresponding
to the desired door position.
Mode Switch
The single rotary Mode Switch has 13 detents to
either direct airflow to the panel outlets, a mix of
floor and panel outlets, floor outlets, a mix of floor
and defrost outlets, or defrost outlets. Rotating the
switch results in the A/C ± Heater Control Module
signaling the actuator to move the mode door. All
door positions are determined relative to the num-
ber of commutator pulses required to provide full
travel of the door. On command, the A/C ± Heater
Control Module runs the actuator for the number of
pulses corresponding to the desired door position.
18
GENERAL INFORMATION

3.9.2.11 HVAC DIAGNOSTICS
The A/C ± Heater Control Module is fully addres-
sable with the DRBIIIt. Two of the Control Mod-
ule's diagnostic capabilities that the DRBIIItwill
actuate include the A/C Cooldown Test to test A/C
system performance and the HVAC Door Recalibra-
tion Test to determine actuator travel span. After
performing either test, the Control Module will
display one or more messages on the DRBIIIt
screen. The message will indicate either that the
HVAC system passed the test or that there is a fault
currently active in the HVAC system. The DRBIIIt
can also extract active and stored Diagnostic Trou-
ble Codes (DTCs) from the control module. Active
DTCs are faults that currently exit in the HVAC
system. Active DTCs cannot be erased until the
condition causing the code is repaired. Stored DTCs
are faults that occurred in the HVAC system since
the control module received the last ªclear diagnos-
tic infoº message.
3.10 CABIN HEATER
NOTE: The Cabin Heater, also known as the
Diesel Cabin Heater Assist (DCHA), will be
referred to as the DCHA throughout most of
the General Information and the Diagnostic
Procedures in this manual.
3.10.1 GENERAL SAFETY INFORMATION
WARNING: DO NOT OPERATE THE DCHA IN
AN ENCLOSED AREA SUCH AS A GARAGE
THAT DOES NOT HAVE EXHAUST
VENTILATION FACILITIES. ALWAYS VENT
THE DCHA's EXHAUST WHEN OPERATING
THE DCHA. FAILURE TO FOLLOW THESE
INSTRUCTIONS MAY RESULT IN PERSONAL
INJURY OR DEATH.
WARNING: ALLOW THE DCHA ASSEMBLY
TO COOL BEFORE PERFORMING A COM-
PONENT INSPECTION/REPAIR/REPLACE-
MENT. FAILURE TO FOLLOW THESE
INSTRUCTIONS MAY RESULT IN PERSONAL
INJURY.
WARNING: ALWAYS DISCONNECT THE
VEHICLE'S BATTERY PRIOR TO PER-
FORMING ANY TYPE OF WORK ON THE
DCHA. FAILURE TO FOLLOW THESE
INSTRUCTIONS MAY RESULT IN PERSONAL
INJURY OR DEATH.WARNING: NEVER ATTEMPT TO REPAIR THE
DCHA HEATER MODULE OR ANY OF ITS
INTERNAL COMPONENTS. ALWAYS PER-
FORM DCHA COMPONENT REPLACEMENT
IN ACCORDANCE WITH THE SERVICE
INFORMATION. FAILURE TO FOLLOW
THESE INSTRUCTIONS MAY RESULT IN
PERSONAL INJURY OR DEATH.
CAUTION: Do not actuate the DCHA Field
Mode Test with the engine off. Failure to
follow these instructions may result in
internal damage to the DCHA Heater Module.
CAUTION: Always Perform The Cabin Heater
Pre-Test Prior To Performing Any Other Cabin
Heater Test For The Test Result To Be Valid.
NOTE: Do not disconnect the vehicle's
battery or the DCHA's main power-supply
while the DCHA is in operation or in
run-down mode. Failure to follow these
instructions may result in excess emissions
from the DCHA Heater Module.
NOTE: Failure to prime the Dosing Pump
after draining the DCHA fuel line will prevent
DCHA heater activation during the first
attempt to start the heater. This will also set a
Diagnostic Trouble Code (DTC) in the DCHA
Control's memory. Do not perform the Dosing
Pump Priming Procedure if an attempt was
made to start the DCHA without priming the
Dosing Pump first. This will put excess fuel
in the DCHA Heater Module and cause smoke
to emit from the DCHA exhaust pipe when
heater activation occurs.
NOTE: Waxed fuel can obstruct the fuel line
and reduce flow. Check for the appropriate
winter grade fuel and replace as necessary.
3.10.2 COMPONENT DESCRIPTION AND
OPERATION
3.10.2.1 DCHA ASSEMBLY
The DCHA is a supplemental heater designed to
pre-heat the engine's coolant in order to supply the
vehicle's occupants with heat prior to the engine
reaching operating temperature. The DCHA assem-
bly mounts underneath the vehicle on the left side
floor pan near the front door opening. The DCHA
assembly connects to the vehicle's heater hoses and
has a fuel supply line that connects to the vehicle's
fuel tank.
19
GENERAL INFORMATION

ating and the combustion air fan operation is sus-
pended for 3 seconds. Subsequently, the combustion
air fan speed is increased in two ramps within 56
seconds to nearly full load operation. After a stabi-
lization phase of 15 seconds, the combustion air fan
speed is again increased in a ramp within 50
seconds to nearly full load. After reaching full load
fuel delivery, the glow plug is deactivated and the
combustion air fan operation is increased to full
load. During the subsequent 45 seconds, as well as
in normal operation, the glow plug functions as a
flame sensor to monitor the flame condition. After
all these events, the automatically controlled heat-
ing operation starts.
In case of a no flame or a flame out condition, a
restart is automatically initiated. If the no flame
condition persists, fuel delivery is stopped and the
heater enters an error lockout mode with a run-
down of the combustion air fan. This will set one or
more DTCs in the DCHA Control's memory. If six
continuous attempts to start the heater fail due to
one or more faults in the DCHA system, the heater
enters a heater lockout mode. This will set DTC
B1813 along with any other fault(s) that the DCHA
Control identified.
3.10.3.2 HEATING
During the automatically controlled heating op-
eration, when the coolant temperature reaches
72ÉC (162ÉF), the heater will switch to a part load
operation. When the coolant temperature reaches
75ÉC (167ÉF) or if the heater runs for longer than 76
minutes the heater will switch to a control idle
period. If the coolant temperature drops to 71ÉC
(160ÉF) during a control idle period, the heater will
perform a regular starting sequence into full load
operation. A drop in coolant temperature to 65ÉC
(149ÉF) during part load operation will cause the
heater to switch to a full load operation.
3.10.3.3 DEACTIVATION
The DCHA will deactivate if the:
²engine is turned off.
²coolant temperature reaches 75ÉC (167ÉF).
²heater runs longer than 76 minutes.
²fuel tank has less than 1/8 of a tank of fuel.
²Power switch on the A/C ± Heater Control Module
is off.
²Blend Control on the A/C ± Heater Control Mod-
ule is set below 75% reheat.
When the heater is deactivated, the combustion
stops and a run-down sequence begins. During the
run-down sequence, the combustion air fan contin-
ues operation to cool down the heater. The fan is
automatically switched off after the run-down se-
quence is complete. The run-down time and thecombustion air fan speed depend on the heater
operating condition at the time of deactivation.
Run-down time is approximately 175 seconds when
deactivated in full load operation and approxi-
mately 100 seconds when deactivated in part load
operation.
3.10.4 DIAGNOSTICS
The DCHA is fully addressable with the DRBIIIt.
System tests include a Field Mode Test to activate
the DCHA for diagnostic testing purposes. The
DCHA Control will store up to three DTCs in its
memory. If the Controller detects a new fault in the
DCHA system, one that is not already stored in its
memory, it will clear the oldest of the three stored
DTCs, and it will store the new fault's DTC. If the
Controller detects a reoccurrence of a stored fault, it
will overwrite that fault's DTC with the most recent
occurrence.
3.11 INSTRUMENT CLUSTER
The Instrument Cluster receives and sends mes-
sages to other modules via the PCI bus circuit. The
indicator lamps will illuminate briefly for a bulb
check when the ignition is turned from off to run.
All of the gauges receive their information via the
PCI bus from the powertrain control module and
body control module.
The gauges and the LEDs are not individually
replaceable thereby requiring complete replace-
ment of the Instrument Cluster if a repair is neces-
sary. In the event that the Instrument Cluster loses
communication with other modules on the PCI bus,
the cluster will display ªno busº in the VF display.
The Trip/Reset button is used to switch the dis-
play from trip to total mileage. Holding the button
when the display is in the trip mode will reset the
trip mileage. This button is also used to put the
cluster in self-diagnostic mode. The odometer dis-
play uses blue-green vacuum fluorescent digital
characters.
On base vehicles, the Instrument Cluster has
three gauges: Speedometer, Fuel and Engine Cool-
ant Temperature. A red dot moves transversely
through openings in the Instrument Cluster face
(P-R-N-D-2-1) to indicate the gear selected.
With all other models, the Instrument Cluster
also includes a Tachometer and uses a vacuum-
fluorescent shift indicator.
The odometer display and door/liftgate ajar indi-
cators turn on when a door is opened to assist both
the customer and service technician to view the
odometer without turning the ignition on.
21
GENERAL INFORMATION

On vehicles equipped with AutoStick, the display
includes an O/D OFF indicator that is illuminated
when the driver presses the Overdrive Off button
on the transaxle shifter.
3.11.1 INSTRUMENT CLUSTER SELF TEST
1. Depress and hold the Odometer Reset button.
2. Turn the ignition switch to the RUN/START
position.
3. Release the Odometer reset button.
The Instrument Cluster will illuminate all indi-
cators and step the gauges through several calibra-
tion points. Also, the odometer will display any
stored codes that may have set.
3.11.2 MESSAGE CENTER
The Message Center is located above the brow of
the Instrument Cluster. It houses the following
warning indicators: Check Engine/Service Engine
Soon, high beam, left and right turn signals, Secu-
rity Alarm Set, and low oil pressure. On base
models equipped with the three-speed transaxle,
these indicators appear in the face of the cluster.
The Security Alarm set indicator is a red circle.
Activation of Instrument Cluster indicators is
coordinated with indicators in the message center
and EVIC to avoid redundancy. A revised safety
standard now requires that the seat belt warning
lamp in the Instrument Cluster remain lit if the
driver seat belt is not buckled. A headlamp out ISO
indicator has been added to the Instrument Cluster
to alert the driver when a headlamp is not function-
ing.
3.12 INTERIOR LIGHTING
3.12.1 COURTESY LAMP CONTROL
The body controller has direct control over all of
the vehicle's courtesy lamps. The body computer
will illuminate the courtesy lamps under any of the
following conditions:
1. Any door ajar and courtesy lamp switch on the
headlamp switch is not in the dome off position.
2. The courtesy lamp switch on the headlamp
switch is in the dome on position.
3. A Remote Keyless Entry unlock message is re-
ceived.
4. Driver door unlocked with key (with VTSS only).
3.12.2 ILLUMINATED ENTRY
Illuminated entry will be initiated when the cus-
tomer enters the vehicle by unlocking the doors
with the key fob, or with the key if the vehicle is
equipped with vehicle theft alarm. Upon exiting thevehicle, if the lock button is pressed with a door
open, illuminated entry will cancel when the door
closes. If the doors are closed and the ignition
switch is turned on, the illuminated entry also
cancels. The illuminated entry feature will not
operate if the courtesy lamp switch is in the dome
off position.
3.12.3 INTERIOR LIGHTING BATTERY
SAVER
If any of the interior lamps are left on after the
ignition is turned off, the BCM will turn them off
after 8 minutes. To return to normal operation, the
courtesy lamps will operate after the dome lamp
switch or door ajar switch changes state. The glove
box and switched reading lamps require that the
ignition be turned to the on/acc position.
3.13 MEMORY SYSTEM
The memory system consists of power driver 's
seat, power mirrors and radio presets. The Memory
Seat/Mirror Module (MSMM) is located under the
driver 's seat. It receives input from the following:
driver 's manual 8-way seat switch, driver 's seat
position sensors, PCI bus circuits, and the power
mirror sensors. The module uses these inputs to
perform the following functions: position the driv-
er 's memory seat, both exterior mirrors (during
recalls), and send/receive the memory system infor-
mation over the PCI bus.
The Memory Set Switch is wired to the Body
Control Module (BCM). When a button (either #1 or
#2) is pressed on the set switch causes the to BCM
send a message to the MSMM which in turn sends
a motion status messages to the BCM. If the BCM
receives no motion from the MSMM it will send a
recall message to the MSMM and radio (once igni-
tion is in run or accessory). The MSMM will in turn
position the drivers seat, both mirrors along with
recalling the radio presets. If the drivers seat or
either exterior mirror is inoperative from its own
respective switches, use the service information
and schematic to diagnose the problem. This man-
ual addresses the memory problems only and it is
assumed there is not a basic component failure.
3.13.1 POWER SEAT
The memory power seat provides the driver with
2 position settings for the driver 's seat. Each power
seat motor is connected to the MSMM with two
motor drive circuits. Each circuit is switched be-
tween battery and ground. By being able to bi-
directionally drive the circuits, the MSMM controls
the movement of the motors based on input from
the power seat switch or from the position sensors
when performing a memory recall. Each motor
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GENERAL INFORMATION