2001 CHRYSLER VOYAGER fan

TABLE OF CONTENTS - Continued
3.9.2.1SYSTEM AVAILABILITY....................................17
3.9.2.2CABIN HEATER..........................................17
3.9.2.3ZONE CONTROL ± SINGLE-ZONE...........................17
3.9.2.4ZONE CONTROL ± DUAL-ZONE.............................17
3.9.2.5AIR DISTRIBUTION.......................................17
3.9.2.6DOOR ACTUATORS.......................................17
3.9.2.7DOOR ACTUATOR CONTROL..............................17
3.9.2.8HVAC SYSTEM RELAYS...................................18
3.9.2.9EVAPORATOR TEMPERATURE SENSOR.....................18
3.9.2.10A/C ± HEATER CONTROL MODULE, SWITCH OPERATION......18
3.9.2.11HVAC DIAGNOSTICS.....................................19
3.10CABIN HEATER...................................................19
3.10.1GENERAL SAFETY INFORMATION..........................19
3.10.2COMPONENT DESCRIPTION AND OPERATION...............19
3.10.2.1DCHA ASSEMBLY.........................................19
3.10.2.2COMBUSTION AIR FAN...................................20
3.10.2.3BURNER HOUSING.......................................20
3.10.2.4BURNER INSERT.........................................20
3.10.2.5CONTROL UNIT/HEAT EXCHANGER.........................20
3.10.2.6DOSING PUMP...........................................20
3.10.3OPERATION.............................................20
3.10.3.1ACTIVATION.............................................20
3.10.3.2HEATING................................................21
3.10.3.3DEACTIVATION...........................................21
3.10.4DIAGNOSTICS...........................................21
3.11INSTRUMENT CLUSTER............................................21
3.11.1INSTRUMENT CLUSTER SELF TEST........................22
3.11.2MESSAGE CENTER.......................................22
3.12INTERIOR LIGHTING...............................................22
3.12.1COURTESY LAMP CONTROL...............................22
3.12.2ILLUMINATED ENTRY.....................................22
3.12.3INTERIOR LIGHTING BATTERY SAVER......................22
3.13MEMORY SYSTEM.................................................22
3.13.1POWER SEAT............................................22
3.13.2MEMORY MIRRORS.......................................23
3.14OVERHEAD CONSOLE.............................................23
3.14.1COMPASS/MINI-TRIP COMPUTER (CMTC)....................23
3.14.2ELECTRONIC VEHICLE INFORMATION CENTER (EVIC)........23
3.14.3SETTING THE COMPASS..................................23
3.14.4SETTING THE VARIANCE..................................23
3.15POWER DOOR LOCK SYSTEM......................................24
3.15.1SLIDING DOOR MEMORY LOCK............................24
3.15.2DOOR LOCK INHIBIT......................................24
3.15.3AUTOMATIC DOOR LOCKS................................24
3.15.4REMOTE KEYLESS ENTRY (RKE)...........................24
3.16POWER FOLDING MIRRORS........................................24
3.17POWER LIFTGATE SYSTEM.........................................25
3.17.1POWER LIFTGATE........................................25
3.17.2DIAGNOSTIC FEATURES..................................25
3.17.3SYSTEM INHIBITORS.....................................25
3.18POWER SLIDING DOOR SYSTEM....................................25
3.18.1POWER SLIDING DOOR...................................25
3.18.2DIAGNOSTIC FEATURES..................................26
ii

TABLE OF CONTENTS - Continued
REMOTE RADIO SWITCH OPEN OR *REMOTE RADIO CONTROLS
INOPERATIVE.........................................................217
REMOTE RADIO SWITCH STUCK........................................219
RIGHT OUTPUT SHORT................................................222
AUTOMATIC TEMPERATURE CONTROL
AC PRESSURE TOO HIGH (ACTIVE)......................................225
AC PRESSURE TOO LOW (ACTIVE)......................................225
AC PRESSURE TOO HIGH (STORED).....................................226
AC PRESSURE TOO LOW (STORED).....................................226
DRIVER BLEND DOOR NOT RESPONDING (STORED)......................226
DRIVER BLEND DOOR RANGE TOO LARGE (STORED).....................226
DRIVER BLEND DOOR TRAVEL TOO SMALL (STORED).....................226
FRONT IR SENSOR AND CONTROL HEAD MISMATCH (STORED).............226
FRONT IR SENSOR CHANGE TOO LARGE (STORED).......................226
FRONT IR SENSOR HIGH (STORED).....................................226
FRONT IR SENSOR LOW (STORED)......................................226
FRONT IR SENSOR NOT CALIBRATED (STORED)..........................226
FRONT KEYBOARD COMMUNICATION FAULT (STORED)....................226
FRONT KEYBOARD FAULT (STORED)....................................226
FRONT MODE DOOR NOT RESPONDING (STORED)........................226
FRONT MODE DOOR TRAVEL TOO LARGE (STORED)......................226
FRONT MODE DOOR TRAVEL TOO SMALL (STORED)......................226
PASS BLEND DOOR NOT RESPONDING (STORED).........................226
PASS BLEND DOOR TRAVEL TOO LARGE (STORED).......................226
PASS BLEND DOOR TRAVEL TOO SMALL (STORED).......................226
PCI BUS SHORTED HIGH (STORED).....................................226
PCI BUS SHORTED LOW (STORED)......................................226
REAR BLEND DOOR NOT RESPONDING (STORED)........................226
REAR BLEND DOOR RANGE TOO LARGE (STORED).......................226
REAR BLEND DOOR TRAVEL TOO SMALL (STORED).......................226
REAR FAN POT OPEN (STORED)........................................226
REAR FAN POT SHORTED (STORED)....................................226
REAR IR SENSOR HIGH (STORED)......................................226
REAR IR SENSOR LOW (STORED).......................................226
REAR IR SENSOR NOT CALIBRATED (STORED)...........................226
REAR KEYBOARD FAULT (STORED).....................................226
REAR MODE DOOR NOT RESPONDING (STORED).........................226
REAR MODE DOOR TRAVEL TOO LARGE (STORED).......................226
REAR MODE DOOR TRAVEL TOO SMALL (STORED)........................226
REAR MODE POT OPEN (STORED)......................................226
REAR MODE POT SHORTED (STORED)..................................226
RECIRC DOOR NOT RESPONDING (STORED).............................226
RECIRC DOOR TRAVEL TOO LARGE (STORED)............................226
RECIRC DOOR TRAVEL TOO SMALL (STORED)............................226
COOLDOWN TEST FAILED..............................................232
DRIVER BLEND DOOR NOT RESPONDING (ACTIVE).......................234
DRIVER BLEND DOOR TRAVEL TOO LARGE (ACTIVE)......................236
DRIVER BLEND DOOR TRAVEL TOO SMALL (ACTIVE)......................238
EEPROM CHECKSUM ERROR (ACTIVE)..................................240
EVAP TEMP SENSOR OPEN............................................241
EVAP TEMP SENSOR SHORTED.........................................243
FRONT IR SENSOR AND CONTROL HEAD MISMATCH (ACTIVE)..............245
viii

TABLE OF CONTENTS - Continued
FRONT IR SENSOR CHANGE TOO LARGE (ACTIVE)........................245
FRONT IR SENSOR HIGH (ACTIVE)......................................245
FRONT IR SENSOR LOW (ACTIVE).......................................245
FRONT IR SENSOR NOT CALIBRATED (ACTIVE)...........................246
FRONT KEYBOARD FAULT (ACTIVE).....................................246
FRONT KEYBOARD COMMUNICATION FAULT (ACTIVE).....................251
FRONT MODE DOOR NOT RESPONDING (ACTIVE).........................252
FRONT MODE DOOR TRAVEL TOO LARGE (ACTIVE).......................254
FRONT MODE DOOR TRAVEL TOO SMALL (ACTIVE).......................256
INVALID CONDITIONS FOR COOLDOWN TEST, EVAP TEMPERATURE TOO
LOW.................................................................258
PASS BLEND DOOR NOT RESPONDING (ACTIVE)..........................261
PASS BLEND DOOR TRAVEL TOO LARGE (ACTIVE)........................263
PASS BLEND DOOR TRAVEL TOO SMALL (ACTIVE)........................265
PCI BUS SHORTED HIGH (ACTIVE)......................................267
PCI BUS SHORTED LOW (ACTIVE).......................................267
REAR BLEND DOOR NOT RESPONDING (ACTIVE).........................268
REAR BLEND DOOR TRAVEL TOO LARGE (ACTIVE)........................270
REAR BLEND DOOR TRAVEL TOO SMALL (ACTIVE)........................272
REAR FAN POT OPEN (ACTIVE).........................................274
REAR FAN POT SHORTED (ACTIVE).....................................274
REAR IR SENSOR HIGH (ACTIVE).......................................274
REAR IR SENSOR LOW (ACTIVE)........................................274
REAR MODE POT OPEN (ACTIVE).......................................274
REAR MODE POT SHORTED (ACTIVE)...................................274
REAR IR SENSOR NOT CALIBRATED (ACTIVE)............................276
REAR KEYBOARD FAULT (ACTIVE)......................................280
REAR MODE DOOR NOT RESPONDING (ACTIVE)..........................284
REAR MODE DOOR TRAVEL TOO LARGE (ACTIVE)........................286
REAR MODE DOOR TRAVEL TOO SMALL (ACTIVE).........................288
RECIRC DOOR NOT RESPONDING (ACTIVE)..............................290
RECIRC DOOR TRAVEL TOO LARGE (ACTIVE).............................292
RECIRC DOOR TRAVEL TOO SMALL (ACTIVE).............................294
CABIN HEATER
CABIN HEATER PRE-TEST..............................................296
CABIN HEATER CONTROL CIRCUIT OPEN (STORED).......................296
CABIN HEATER CONTROL CIRCUIT SHORT TO BATTERY (STORED)..........296
B1000 CONTROL UNIT ERRONEOUS.....................................299
B1800 NO START......................................................300
B1801 FLAME OUT: DURING HEATING CYCLE.............................300
B1801 FLAME OUT: UNSTABLE OPERATION...............................300
B1802 POWER SUPPLY OUT OF RANGE: LOW VOLTAGE THRESHOLD........304
B1802 POWER SUPPLY OUT OF RANGE: VOLTAGE ABOVE 15.5 VOLTS.......307
B1803 FLAME DETECTED PRIOR TO COMBUSTION........................308
B1811 HEATER OVERHEATED...........................................309
B1813 HEATER IN LOCKOUT MODE......................................313
B1820 DOSING PUMP CIRCUIT: OPEN OR SHORT TO BATTERY.............315
B1820 DOSING PUMP CIRCUIT: SHORT TO GROUND.......................318
B1821 COMBUSTION AIR FAN CIRCUIT: OPEN.............................321
B1821 COMBUSTION AIR FAN CIRCUIT: SHORT TO GROUND................321
B1822 GLOW PIN/FLAME SENSOR: OPEN................................322
B1822 GLOW PIN/FLAME SENSOR: SHORT TO GROUND...................322
ix

TABLE OF CONTENTS - Continued
B1823 WATER PUMP CIRCUIT: OPEN.....................................323
B1823 WATER PUMP CIRCUIT: SHORT TO GROUND........................323
B1824 FAN SWITCH LINE SHORT TO GROUND............................324
CABIN HEATER CONTROL CIRCUIT OPEN (ACTIVE)........................325
CABIN HEATER CONTROL CIRCUIT SHORT TO BATTERY (ACTIVE)...........329
*CABIN HEATER INOPERABLE FROM A/C - HEATER MODULE...............332
CHIME
*CHIME INOPERATIVE..................................................334
*KEY IN IGNITION AND DRIVER'S DOOR OPEN CHIME NOT OPERATING
PROPERLY...........................................................336
*PROBLEM WITH THE HIGH VEHICLE SPEED WARNING CHIME.............337
COMMUNICATION
ATC MESSAGES NOT RECEIVED........................................338
AUDIO MESSAGES NOT RECEIVED......................................339
BCM, PCI BUS SHORTED TO BATTERY...................................340
BCM, PCI BUS SHORTED TO GROUND...................................340
FCM, PCI BUS SHORTED TO BATTERY...................................340
FCM, PCI BUS SHORTED TO GROUND...................................340
COUNTRY CODE NOT PROGRAMMED...................................342
FCM MESSAGES NOT RECEIVED........................................343
FCM, BCM COMMUNICATION FAULT.....................................344
FCM, HVAC COMMUNICATION FAULT....................................345
FCM, PCI INTERNAL FAULT.............................................346
FCM, PCM COMMUNICATION FAULT.....................................347
FCM, RADIO COMMUNICATION FAULT...................................348
FCM, TCM COMMUNICATION FAULT.....................................349
IGNITION MUX SWITCH INPUT OPEN....................................350
IGNITION MUX SWITCH INPUT SHORT...................................352
IGNITION RUN OUTPUT SHORT.........................................353
INTERNAL BCM FAILURE...............................................357
LEFT PSD MESSAGES NOT RECEIVED...................................358
LIFTGATE MODULE MESSAGES NOT RECEIVED...........................359
MIC MESSAGES NOT RECEIVED........................................360
MSM MESSAGES NOT RECEIVED.......................................361
NO PCI MESSAGES FROM CD CHANGER.................................362
ORC MESSAGES NOT RECEIVED........................................364
OTIS MESSAGES NOT RECEIVED.......................................365
PCI INTERNAL HARDWARE FAILURE.....................................366
PCM MESSAGES NOT RECEIVED........................................367
RADIO MEM MSG NOT RECEIVED.......................................368
RIGHT PSD MESSAGES NOT RECEIVED..................................369
RUN/START HARDWIRE INPUT FAILURE..................................370
SKIM MESSAGES NOT RECEIVED.......................................371
TCM MESSAGES NOT RECEIVED........................................372
*BUS +/- SIGNALS OPEN FROM AUTOMATIC TEMPERATURE CONTROL
MODULE.............................................................373
*BUS +/- SIGNALS OPEN FROM MEMORY SEAT/MIRROR MODULE...........375
*BUS +/- SIGNALS OPEN FROM SENTRY KEY IMMOBILIZER MODULE........377
*BUS +/- SIGNALS OPEN OR NO RESPONSE FROM BODY CONTROL
MODULE.............................................................379
*BUS +/- SIGNALS OPEN OR NO RESPONSE FROM HVAC..................381
x

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

the CPA is not properly engaged, a voltage on pin 38
will be interpreted as an unseated connector and a
fault will set.
Flash programming voltage Ð20 volt input on
pin 42. When a DRBIIItis connected and the
proper flash reprogramming sequence is selected,
the 20 volt signal will be applied through pin 42.
3.9 HEATING & A/C
3.9.1 AUTOMATIC TEMPERATURE
CONTROL (ATC)
3.9.1.1 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.
3.9.1.2 SYSTEM OPERATION
The Automatic Temperature Control (ATC) sys-
tem provides fully adjustable three zone climate
control; Driver front zone, Passenger Front zone
and Rear zone. The following is a list of ATC
controls and features:
± a POWER button which allows the operator to
turn the system completely off.
± AUTO HIGH/LOW switch allows the operator
to select what rate (fan speed) the system will
provide the selected comfort level.
± DRIVER, REAR and PASSENGER rocker
switches to select desired temperature for each
zone.
± Recirculation button allows cooling air to be
recirculated which maximizes cooling ability.
± A/C select button allows the operator to turn
the A/C compressor off.
± Defroster button allows the operator to turn on
the defroster independently during automatic
control.
± Fan control rotary switch for selecting fan
speed.
± Mode rotary switch for selecting heating/
cooling direction.
± REAR SYSTEM rotary switch for activating
the Rear ATC Switch allowing intermediate
passenger control over rear climate control.
3.9.1.3 BLOWER MOTOR OPERATION
The Automatic Temperature Control (ATC) front
and rear blower control provides continuously vari-
able control of air flow rate to meet occupant
comfort requirements. Pulse width modulation of
the blower motor power allows the front and rear
blower to operate at any speed from off to full speed.
When front or rear blower operation is required, the
ATC sends a PCI Bus message to the Front Control
Module (FCM) requesting blower relay ON. The
FCM provides a ground for the front and rear
blower motor relay coils, activating both relays. The
front and rear blower relays provide 12 volts to
their respective blower motor power modules. Each
module provides a 12 volt blower motor control
signal to the ATC. The ATC provides a pulse width
modulated (duty-cycle) ground signal to this circuit
based on climate requirements. The higher voltage
on the signal circuit (less duty-cycle ground) the
lower the blower speed request. The lower voltage
on the signal circuit (more duty-cycle ground) the
higher the blower speed request.
3.9.1.4 INFRARED SENSORS
The ATC system uses infrared (I/R) sensors to
monitor and control oocupant comfort levels. This
sensing system replaces interior air temperature
and solar sensors which required complex control
programs to maintain occupant comfort levels. The
front I/R sensor is located in the instrument panel
center bezel outlet. The rear I/R sensor is located in
the rear overhead mounted ATC switch.
3.9.1.5 REAR ATC SWITCH
The rear ATC switch is mounted in the headliner.
The switch contains a rotary adjustment for fan
speed, a rotary adjustment for mode selection, a
push button switch for temperature selection and a
digital display of the selected temperature.
3.9.1.6 COOLDOWN TESTING
The ATC provides a feature referred to as a
Cooldown Test. This test is initiated using the
DRBIIItand is designed to check the performance
of the air conditioning system. The ATC will not
perform this test if the ambient air temperature is
below 12ÉC (53ÉF). During the test, the ATC com-
pares the ambient air temperature to the evapora-
tor temperature sensor. To pass the cooldown test,
the evap temperature sensor must drop -6ÉC (20ÉF)
below ambient temperature within 2 minutes of
start of test. At the completion of the cooldown test
the DRBIIItwill display one of the following mes-
sages indicating test outcome:
± Cooldown Test Passed
± Cooldown Test Failed
16
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

The DCHA assembly consists of a:
²combustion air fan assembly
²burner housing
²burner insert
²control unit/heat exchanger
²combustion chamber
²dosing pump
3.10.2.2 COMBUSTION AIR FAN
The combustion air fan assembly includes the:
²combustion air fan
²combustion air fan inlet
²fuel supply inlet
The combustion air fan delivers the air required
for combustion from the combustion air inlet to the
burner insert.
3.10.2.3 BURNER HOUSING
The burner housing includes the:
²coolant inlet
²coolant outlet
²exhaust outlet
The burner housing accommodates the burner
insert and is combined with the control unit/heat
exchanger as an assembly.
3.10.2.4 BURNER INSERT
The burner insert includes the:
²combustion pipe fuel cross section
²glow plug/flame sensor
Inside the burner insert fuel is distributed across
the combustion pipe fuel cross section. Combustion
of the fuel/air mixture takes place within the com-
bustion pipe to heat the exchanger. The glow plug/
flame sensor located in the burner insert ignites the
fuel/air mixture during heater start up. After heater
start up, the glow plug/flame sensor operates in the
flame sensor function. The glow plug/flame sensor
designed as an electrical resistor is located in the
burner insert opposite the flame side.
3.10.2.5 CONTROL UNIT/HEAT
EXCHANGER
The control unit/heat exchanger includes the:
²control unit
²temperature sensor
²overheat protection
²heat exchanger
²connector terminal
The control unit controls and monitors combus-
tion operation. The control unit is ventilated bymeans of a ventilation hose routed from the com-
bustion air collector compartment of the burner.
The heat exchanger transfers the heat generated by
combustion to the coolant circuit. The control unit/
heat exchanger and the burner housing are an
assembly and must not be disassembled.
The temperature sensor senses the coolant tem-
perature in the heat exchanger as an electrical
resistance. This signal is sent to the control unit for
processing.
The overheat protection, controlled by the tem-
perature resistor, protects the heater against undue
operating temperatures. The overheat protection
will switch the heater off if the water temperature
exceeds 105ÉC (221ÉF).
3.10.2.6 DOSING PUMP
The dosing pump is a combined delivery, dosing,
and shut-off system for the fuel supply of the heater.
The dosing pump receives its supply of fuel from the
vehicle's fuel tank.
3.10.3 OPERATION
3.10.3.1 ACTIVATION
When the ignition is in Run, the FCM monitors
the PCI bus for the Cabin Heater Activation re-
quest. The A/C ± Heater Control Module initiates
this request only when all conditions for Cabin
Heater activation are favorable (see below). 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.
The DCHA will activate only when the:
²engine is running.
²coolant temperature is below 66ÉC (151ÉF).
²fuel tank has greater than 1/8 of a tank of fuel.
²Power switch on the A/C ± Heater Control Module
is on.
²Blend Control on the A/C ± Heater Control Mod-
ule is set above 95% reheat.
²Front Control Module (FCM) sees the Cabin
Heater Activation request that is bussed from the
A/C ± Heater Control Module.
When the DCHA starting sequence begins, the
glow plug and the combustion air fan are activated.
After 30 seconds, the fuel dosing pump begins oper-
20
GENERAL INFORMATION