relay CHRYSLER VOYAGER 2001 Service Manual

and is accessed for service by rolling down the glove
box from the instrument panel.
The power module heat sink will get hot when in
use. Do not touch the heat sink if the blower motor
has been running. The blower power module cannot
be adjusted or repaired and, if faulty or damaged, it
must be replaced.
OPERATION
The blower power module is connected to the vehi-
cle electrical system through a dedicated take out
and connector of the instrument panel wire harness.
A second connector receptacle receives the pigtail
wire connector from the blower motor. The blower
power module allows the microprocessor-based Auto-
matic Temperature Control (ATC) heater-A/C control
module to calculate and provide infinitely variable
blower motor speeds based upon either manual
blower switch input or the ATC programming using a
Pulse Width Modulated (PWM) circuit strategy. The
PWM voltage is applied to a comparator circuit
which compares the PWM signal voltage to the
blower motor feedback voltage. The resulting output
drives the power module circuitry, which adjusts the
voltage output received from the blower motor relay
to change or maintain the desired blower speed. The
blower power module is diagnosed using a DRBIIIt
scan tool. Refer to the appropriate diagnostic infor-
mation.
REMOVAL
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE AIRBAG SYSTEM BEFORE
ATTEMPTING ANY STEERING WHEEL, STEERING
COLUMN, 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.
(2) Open the glove box.
(3) Flex both sides of the glove box bin inward
near the top far enough for the rubber glove box stop
bumpers to clear the sides of the glove box opening,
then roll the glove box downward.
(4) Reach through the glove box opening to access
and disconnect the instrument panel wire harness
connector for the power module from the module con-
nector receptacle.
(5) Reach through the glove box opening to access
and disconnect the blower motor pigtail wire connec-
tor from the power module connector receptacle.
(6) Remove the two screws that secure the power
module to the evaporator housing.
(7) Remove the power module from the evaporator
housing.
INSTALLATION
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE AIRBAG SYSTEM BEFORE
ATTEMPTING ANY STEERING WHEEL, STEERING
COLUMN, 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) Position the power module into the evaporator
housing.
Fig. 23 Power Module
1 - POWER MODULE
2 - LOWER GLOVE BOX OPENING REINFORCEMENT
3 - EVAPORATOR HOUSING
RSCONTROLS - FRONT24-27
POWER MODULE (Continued)

CONTROLS - REAR
TABLE OF CONTENTS
page page
A/C-HEATER CONTROL
REMOVAL..............................30
INSTALLATION...........................31
BLEND DOOR ACTUATOR
DESCRIPTION...........................31
OPERATION.............................31
REMOVAL..............................32
INSTALLATION...........................32
BLOWER MOTOR RELAY
DESCRIPTION...........................33
OPERATION.............................33
DIAGNOSIS AND TESTING.................34
BLOWER MOTOR RELAY.................34
REMOVAL..............................34
INSTALLATION...........................34
BLOWER MOTOR RESISTOR
DESCRIPTION...........................35
OPERATION.............................35
DIAGNOSIS AND TESTING.................35BLOWER MOTOR RESISTOR.............35
REMOVAL..............................36
INSTALLATION...........................36
EXPANSION VALVE SOLENOID
DESCRIPTION...........................36
OPERATION.............................37
INFRARED TEMPERATURE SENSOR
DESCRIPTION...........................37
OPERATION.............................37
MODE DOOR ACTUATOR
DESCRIPTION...........................37
OPERATION.............................38
REMOVAL..............................38
INSTALLATION...........................38
POWER MODULE
DESCRIPTION...........................39
OPERATION.............................39
REMOVAL..............................40
INSTALLATION...........................40
A/C-HEATER CONTROL
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Using a trim stick or another suitable wide flat
bladed tool, gently pry the top edge of the rear heat-
er-A/C control bezel away from the headliner far
enough to release the two snap clip retainers (Fig. 1).
(3) Pull the rear heater-A/C control and bezel unit
rearward far enough to access the headliner wire
harness connector on the back of the control.
(4) Disconnect the headliner wire harness connec-
tor for the rear heater-A/C control from the control
connector receptacle.
(5) Remove the rear heater-A/C control from the
headliner.
(6) Remove the three screws that secure the rear
heater-A/C control to the bezel (Fig. 2).
(7) Remove the rear heater-A/C control from the
bezel.
Fig. 1 Heater-A/C Control
1 - TRIM STICK
2 - BEZEL
3 - HEATER-A/C CONTROL
4 - HEADLINER
24 - 30 CONTROLS - REARRS

quarter inner panel. Tighten the screw to 11 N´m (97
in. lbs.).
(7) Install and tighten the screw that secures the
back of the rear heater-A/C unit housing to the right
D-pillar. Tighten the screw to 11 N´m (97 in. lbs.).
(8) Install and tighten the two screws that secure
the top of the quarter trim panel attaching bracket to
the quarter inner panel. Tighten the screws to 1.7
N´m (15 in. lbs.).
(9) Reinstall the right quarter trim panel and
right D-pillar trim panel onto the quarter inner
panel. (Refer to 23 - BODY/INTERIOR/QUARTER
TRIM PANEL - INSTALLATION).
(10) Reconnect the battery negative cable.
(11) Perform the heater-A/C control calibration
procedure. (Refer to 24 - HEATING & AIR CONDI-
TIONING/CONTROLS - FRONT/A/C-HEATER CON-
TROL - STANDARD PROCEDURE - HEATER-A/C
CONTROL CALIBRATION).
BLOWER MOTOR RELAY
DESCRIPTION
TERMINAL LEGEND
NUMBER IDENTIFICATION
30 COMMON FEED
85 COIL GROUND
86 COIL BATTERY
87 NORMALLY OPEN
87A NORMALLY CLOSED
The blower motor relay (Fig. 5) is a International
Standards Organization (ISO) mini-relay. Relays con-
forming to the ISO specifications have common phys-ical dimensions, current capacities, terminal
patterns, and terminal functions. The ISO mini-relay
terminal functions are the same as a conventional
ISO relay. However, the ISO mini-relay terminal pat-
tern (or footprint) is different, the current capacity is
lower, and the physical dimensions are smaller than
those of the conventional ISO relay. The blower
motor relay is located in the Intelligent Power Mod-
ule (IPM), which is in the engine compartment near
the battery. See the fuse and relay layout map
molded into the inner surface of the IPM cover for
compressor clutch relay identification and location.
The black, molded plastic case is the most visible
component of the blower motor relay. Five male
spade-type terminals extend from the bottom of the
base to connect the relay to the vehicle electrical sys-
tem, and the ISO designation for each terminal is
molded into the base adjacent to each terminal. The
ISO terminal designations are as follows:
²30 (Common Feed)- This terminal is con-
nected to the movable contact point of the relay.
²85 (Coil Ground)- This terminal is connected
to the ground feed side of the relay control coil.
²86 (Coil Battery)- This terminal is connected
to the battery feed side of the relay control coil.
²87 (Normally Open)- This terminal is con-
nected to the normally open fixed contact point of the
relay.
²87A (Normally Closed)- This terminal is con-
nected to the normally closed fixed contact point of
the relay.
The factory-installed blower motor relay cannot be
adjusted or repaired. If the relay is damaged or
faulty, it must be replaced.
OPERATION
The blower motor relay is an electromechanical
switch that uses a low current input from the Front
Control Module (FCM) to control the high current
output to the blower motor resistor (manual heater-
A/C control) or blower power module (automatic heat-
er-A/C control). The movable common feed contact
point is held against the fixed normally closed con-
tact point by spring pressure. When the relay coil is
energized, an electromagnetic field is produced by the
coil windings. This electromagnetic field draws the
movable relay contact point away from the fixed nor-
mally closed contact point, and holds it against the
fixed normally open contact point. When the relay
coil is de-energized, spring pressure returns the mov-
able contact point back against the fixed normally
closed contact point. The resistor or diode is con-
nected in parallel with the relay coil in the relay, and
helps to dissipate voltage spikes and electromagnetic
interference that can be generated as the electromag-
netic field of the relay coil collapses.
Fig. 5 Blower Motor Relay
RSCONTROLS - REAR24-33
BLEND DOOR ACTUATOR (Continued)

The blower motor relay terminals are connected to
the vehicle electrical system through a receptacle in
the Intelligent Power Module (IPM). The inputs and
outputs of the compressor clutch relay include:
²The common feed terminal (30) receives a bat-
tery current input from the battery through a B(+)
circuit at all times.
²The coil ground terminal (85) receives a ground
input through the front/rear blower motor relay con-
trol circuit only when the FCM electronically pulls
the control circuit to ground.
²The coil battery terminal (86) receives a battery
current input from the battery through a B(+) circuit
at all times.
²The normally open terminal (87) provides a bat-
tery current output to the blower motor resistor
(manual heater-A/C control) or blower power module
(automatic heater-A/C control) through a fuse in the
IPM on the fused rear blower motor relay output cir-
cuit only when the blower motor relay coil is ener-
gized.
²The normally closed terminal (87A) is not con-
nected to any circuit in this application, but provides
a battery current output only when the blower motor
relay coil is de-energized.
Refer to the appropriate wiring information. The
wiring information includes wiring diagrams, proper
wire and connector repair procedures, further details
on wire harness routing and retention, as well as
pin-out and location views for the various wire har-
ness connectors, splices, and grounds.
DIAGNOSIS AND TESTING - BLOWER MOTOR
RELAY
The rear blower motor relay (Fig. 5) is located in
the Intelligent Power Module (IPM), which is in the
engine compartment near the battery. See the fuse
and relay layout map molded into the inner surface
of the IPM cover for rear blower motor relay identi-
fication and location. Remove the relay from the IPM
to perform the following tests:
(1) A relay in the de-energized position should
have continuity between terminals 87A and 30, and
no continuity between terminals 87 and 30. If OK, go
to Step 2. If not OK, replace the faulty relay.
(2) Resistance between terminals 85 and 86 (elec-
tromagnet) should be 7565 ohms. If OK, go to Step
3. If not OK, replace the faulty relay.
(3) Connect a battery to terminals 85 and 86.
There should now be continuity between terminals
30 and 87, and no continuity between terminals 87A
and 30. If OK, use a DRBIIItscan tool to perform
further diagnosis of the relay circuits. Refer to the
appropriate diagnostic information. If not OK,
replace the faulty relay.
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Unlatch and remove the cover from the Intelli-
gent Power Module (IPM) (Fig. 6).
(3) See the fuse and relay layout map molded into
the inner surface of the IPM cover for rear blower
motor relay identification and location.
(4) Remove the rear blower motor relay from the
IPM.
INSTALLATION
(1) See the fuse and relay layout map molded into
the inner surface of the Intelligent Power Module
(IPM) cover for rear blower motor relay identification
and location (Fig. 6).
(2) Position the rear blower motor relay to the
proper receptacle in the IPM.
(3) Align the rear blower motor relay terminals
with the terminal cavities in the IPM relay recepta-
cle.
(4) Push down firmly on the rear blower motor
relay until the terminals are fully seated in the ter-
minal cavities in the IPM receptacle.
(5) Install and latch the cover onto the IPM.
(6) Reconnect the battery negative cable.
Fig. 6 Intelligent Power Module
1 - BATTERY THERMAL GUARD
2 - INTELLIGENT POWER MODULE
3 - FRONT CONTROL MODULE
24 - 34 CONTROLS - REARRS
BLOWER MOTOR RELAY (Continued)

OPERATION
The rear expansion valve solenoid is designed to
control the flow of refrigerant to the rear evaporator.
The solenoid receives fused battery current through
the rear blower motor relay on a fused rear blower
motor relay output circuit, and receives a ground
feed from the front ATC heater-A/C control module
on a TXV solenoid feed circuit. The front ATC heater-
A/C control module is programmed to control solenoid
operation. When the solenoid blocks refrigerant flow
to the rear evaporator, the resulting increase in the
refrigerant circulation rate between the condenser
and the front evaporator provides improved A/C cool-
ing performance for the front seat occupants. The
solenoid may be diagnosed using a DRBIIItscan
tool. Refer to the appropriate diagnostic information.
INFRARED TEMPERATURE
SENSOR
DESCRIPTION
The rear infrared temperature sensor consists of
an infrared transducer that is concealed behind the
lens of the rear heater-A/C control in the headliner.
This sensor is used only on models equipped with the
optional Automatic Temperature Control (ATC) heat-
ing and air conditioning system. The rear infrared
temperature sensor is integral to the rear heater-A/C
control. The infrared sensor cannot be adjusted orrepaired and, if faulty or damaged, the rear heater-
A/C control unit must be replaced.
OPERATION
The rear infrared temperature sensor provides an
independent measurement input to the Automatic
Temperature Control (ATC) heater-A/C control mod-
ule that indicates the surface temperature of the rear
seat occupants. By using a surface temperature mea-
surement, rather than an air temperature measure-
ment, the ATC system is able to adjust itself to the
comfort level as perceived by the occupant. This
allows the system to detect and compensate for other
ambient conditions affecting comfort levels, such as
solar heat gain or evaporative heat loss. The ATC
system logic responds to the infrared sensor input by
calculating and adjusting the air flow temperature
and air flow rate needed to properly obtain and
maintain the selected comfort level temperatures for
the rear seat occupants. The ATC heater-A/C control
module continually monitors the infrared sensor cir-
cuit, and will store a Diagnostic Trouble Code (DTC)
for any problem it detects. This DTC information can
be retrieved and the infrared temperature sensor
diagnosed using a DRBIIItscan tool. Refer to the
appropriate diagnostic information.
MODE DOOR ACTUATOR
DESCRIPTION
Fig. 9 Expansion Valve Solenoid
1 - SOLENOID
2 - SOLENOID CONNECTOR
3 - SEALING PLATE
4 - EXPANSION VALVE
5 - SEALING PLATE
6 - HVAC CONNECTOR
Fig. 10 Mode Door Actuator
1 - SCREW (2)
2 - MODE DOOR ACTUATOR
3 - SCREW (2)
4 - CONNECTOR
5 - BLEND DOOR ACTUATOR
6 - CONNECTOR
RSCONTROLS - REAR24-37
EXPANSION VALVE SOLENOID (Continued)

voltage is applied to a comparator circuit which com-
pares the PWM signal voltage to the blower motor
feedback voltage. The resulting output drives the
power module circuitry, which adjusts the voltage
output received from the blower motor relay to
change or maintain the desired blower speed. The
blower power module is diagnosed using a DRBIIIt
scan tool. Refer to the appropriate diagnostic infor-
mation.
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Remove the right quarter trim panel and right
D-pillar trim panel from the quarter inner panel.
(Refer to 23 - BODY/INTERIOR/QUARTER TRIM
PANEL - REMOVAL).
(3) Disconnect the rear HVAC wire harness con-
nector for the blower power module from the resistor
connector receptacle (Fig. 13).
(4) Disconnect the blower motor pigtail wire con-
nector from the blower power module connector
receptacle.
(5) Remove the two screws that secure the blower
power module to the rear heater-A/C unit housing.
(6) Remove the blower power module from the rear
heater-A/C unit housing.
INSTALLATION
(1) Position the blower power module into the rear
heater-A/C unit housing (Fig. 13).
(2) Install and tighten the two screws that secure
the blower power module to the rear heater-A/C unit
housing. Tighten the screws to 2 N´m (17 in. lbs.).
(3) Reconnect the blower motor pigtail wire to the
blower power module connector receptacle.
(4) Reconnect the rear HVAC wire harness connec-
tor for the blower power module to the module con-
nector receptacle.
(5) Reinstall the right quarter trim panel and
right D-pillar trim panel onto the quarter inner
panel. (Refer to 23 - BODY/INTERIOR/QUARTER
TRIM PANEL - INSTALLATION).
(6) Reconnect the battery negative cable.
Fig. 13 Power Module
1 - REAR HEATER-A/C UNIT HOUSING
2 - SCREW (2)
3 - D-PILLAR
4 - BLOWER PIGTAIL WIRE
5 - REAR HVAC WIRE HARNESS
6 - EXPANSION VALVE
7 - EXPANSION VALVE SOLENOID
8 - BLOWER POWER MODULE
24 - 40 CONTROLS - REARRS
POWER MODULE (Continued)

BLOWER MOTOR
DESCRIPTION
The blower motor is a 12-volt, Direct Current (DC)
motor with a squirrel cage-type blower wheel that is
secured to the blower motor shaft (Fig. 7). The
blower motor and wheel are located near the passen-
ger side end of the heater-A/C unit within the two
halves of the intake air housing in the passenger
compartment below the instrument panel. The
instrument panel must be rolled rearward to access
the blower motor and blower wheel for service. The
blower motor and blower motor wheel are a factory
balanced unit and cannot be adjusted or repaired. If
faulty or damaged, the blower motor and blower
wheel must be replaced as a unit.
OPERATION
The blower motor will operate whenever the igni-
tion switch is in the On position and the heater-A/C
control power is turned on. The blower motor can
only be turned off by turning off the power at the
heater-A/C control. The blower motor receives battery
current whenever the front blower motor relay is
energized. The front blower motor relay output cir-
cuit is protected by a fuse in the Intelligent Power
Module (IPM) located in the engine compartment
near the battery. In the Manual system, the blower
motor speed is controlled by regulating the path to
ground through the blower control switch and the
blower motor resistor. In the ATC system, the blower
motor speed is controlled by an electronic blower
power module, which uses a pulse width modulated
input from the ATC module and feedback from the
blower motor to regulate the blower motor ground
path it provides. The blower motor and wheel are
used to control the velocity of air moving through the
heater-A/C unit housing. The blower motor controls
the velocity of the air flowing through the heater-A/C
housing by spinning the blower wheel within the
housing at the selected speed or, in the ATC system,
at the selected or programmed speed.
DIAGNOSIS AND TESTING - FRONT BLOWER
MOTOR
BLOWER MOTOR INOPERATIVE
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE AIRBAG SYSTEM BEFORE
ATTEMPTING ANY STEERING WHEEL, STEERING
COLUMN, 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.
Fig. 7 Blower Motor
1 - BLOWER MOTOR
2 - RUBBER GROMMET
3 - BLOWER MOTOR CONNECTOR
4 - MOUNTING TABS
RSDISTRIBUTION - FRONT24-45

(1) Check the fuse (Fuse 10 - 40 ampere) in the
Intelligent Power Module (IPM). If OK, go to Step 2.
If not OK, repair the shorted circuit or component as
required and replace the faulty fuse.
(2) Turn the ignition switch to the On position. Be
certain that the heater-A/C control power is turned
on. Check for battery voltage at the fuse (Fuse 10 -
40 ampere) in the IPM. If OK, go to Step 3. If not
OK, proceed to diagnosis of the front blower motor
relay. (Refer to 24 - HEATING & AIR CONDITION-
ING/CONTROLS - FRONT/BLOWER MOTOR
RELAY - DIAGNOSIS AND TESTING).
(3) Turn the ignition switch to the Off position.
Disconnect and isolate the battery negative cable.
Disconnect the front HVAC wire harness connector
for the front blower motor resistor (Manual Temper-
ature Control) or the front blower power module
(Automatic Temperature Control) from the resistor or
module connector receptacle. Reconnect the battery
negative cable. Turn the ignition switch to the On
position. Be certain that the heater-A/C control
power is turned on. Check for battery voltage at the
fused front blower motor relay output circuit cavity
of the front HVAC wire harness connector for thefront blower motor resistor (MTC) or the front blower
power module (ATC). If OK, go to Step 4. If not OK,
repair the open fused front blower motor relay output
circuit to the IPM as required.
(4) Turn the ignition switch to the Off position.
Disconnect and isolate the battery negative cable.
Disconnect the front blower motor pigtail wire con-
nector from the connector receptacle of the front
blower motor resistor (MTC) or the front blower
power module (ATC). Use jumper wires to connect a
battery and ground feeds to the blower motor pigtail
wire connector. The blower motor should operate. If
OK with MTC, proceed to diagnosis of the front
blower motor resistor. (Refer to 24 - HEATING & AIR
CONDITIONING/CONTROLS - FRONT/BLOWER
MOTOR RESISTOR - DIAGNOSIS AND TESTING).
If OK with ATC, use a DRBIII scan tool to diagnose
the front blower power module. Refer to the appropri-
ate diagnostic information. If not OK with MTC or
ATC, replace the faulty front blower motor.
BLOWER MOTOR NOISE OR VIBRATION
Refer to the Blower Motor Noise/Vibration Diagno-
sis chart (Fig. 8).
24 - 46 DISTRIBUTION - FRONTRS
BLOWER MOTOR (Continued)

system control switch on the front heater-A/C control
is not in the Off position. The blower motor can only
be turned off by turning off the rear system at the
front heater-A/C control. The blower motor receives
battery current whenever the rear blower motor
relay is energized. The rear blower motor relay out-
put circuit is protected by a fuse in the Intelligent
Power Module (IPM) located in the engine compart-
ment near the battery. In the MTC system, the
blower motor speed is controlled by regulating the
path to ground through the blower control switch and
the blower motor resistor. In the ATC system, the
blower motor speed is controlled by an electronic
blower power module, which uses a pulse width mod-
ulated input from the ATC module and feedback from
the blower motor to regulate the blower motor
ground path it provides. The blower motor and wheel
are used to control the velocity of air moving through
the rear heater-A/C unit housing. The blower motor
controls the velocity of the air flowing through the
rear heater-A/C housing by spinning the blower
wheel within the housing at the selected speed or, in
the ATC system, at the selected or programmed
speed.
DIAGNOSIS AND TESTING - REAR BLOWER
MOTOR
BLOWER MOTOR INOPERATIVE
(1) Check the fuse (Fuse 12 - 25 ampere) in the
Intelligent Power Module (IPM). If OK, go to Step 2.
If not OK, repair the shorted circuit or component as
required and replace the faulty fuse.
(2) Turn the ignition switch to the On position. Be
certain that the rear heater-A/C control power is
turned on. Check for battery voltage at the fuse
(Fuse 12 - 25 ampere) in the IPM. If OK, go to Step
3. If not OK, proceed to diagnosis of the rear blower
motor relay. (Refer to 24 - HEATING & AIR CONDI-TIONING/CONTROLS - REAR/BLOWER MOTOR
RELAY - DIAGNOSIS AND TESTING).
(3) Turn the ignition switch to the Off position.
Disconnect and isolate the battery negative cable.
Disconnect the rear HVAC wire harness connector for
the rear blower motor resistor (Manual Temperature
Control) or the rear blower power module (Automatic
Temperature Control) from the resistor or module
connector receptacle. Reconnect the battery negative
cable. Turn the ignition switch to the On position. Be
certain that the rear heater-A/C control power is
turned on. Check for battery voltage at the fused
rear blower motor relay output circuit cavity of the
rear HVAC wire harness connector for the rear
blower motor resistor (MTC) or the rear blower
power module (ATC). If OK, go to Step 4. If not OK,
repair the open fused front blower motor relay output
circuit to the IPM as required.
(4) Turn the ignition switch to the Off position.
Disconnect and isolate the battery negative cable.
Disconnect the rear blower motor pigtail wire connec-
tor from the take out and connector of the rear
HVAC wire harness (MTC) or the connector recepta-
cle of the rear blower power module (ATC). Use
jumper wires to connect a battery and ground feeds
to the blower motor pigtail wire connector. The
blower motor should operate. If OK with MTC, pro-
ceed to diagnosis of the rear blower motor resistor.
(Refer to 24 - HEATING & AIR CONDITIONING/
CONTROLS - REAR/BLOWER MOTOR RESISTOR -
DIAGNOSIS AND TESTING). If OK with ATC, use a
DRBIII scan tool to diagnose the rear blower power
module. Refer to the appropriate diagnostic informa-
tion. If not OK with MTC or ATC, replace the faulty
rear blower motor.
BLOWER MOTOR NOISE OR VIBRATION
Refer to the Blower Motor Noise/Vibration Diagno-
sis chart (Fig. 4).
24 - 56 DISTRIBUTION - REARRS
BLOWER MOTOR (Continued)

²Vehicle Speed Sensor
²Engine Coolant Temperature Sensor
²Throttle Position Sensor
²Engine Controller Self Test Faults
²Cam or Crank Sensor
²Injector and Coil
²Idle Air Control Motor
²EVAP Electrical
²EGR Solenoid Electrical
²Intake Air Temperature
²5 Volt Feed
ConflictÐThe Task Manager does not run the
Oxygen Sensor Monitor if any of the following condi-
tions are present:
²A/C ON (A/C clutch cycling temporarily sus-
pends monitor)
²Purge flow in progress
²Ethanel content learn is takeng place and the
ethenal used once flag is set
SuspendÐThe Task Manager suspends maturing
a fault for the Oxygen Sensor Monitor if an of the fol-
lowing are present:
²Oxygen Sensor Heater Monitor, Priority 1
²Misfire Monitor, Priority 2
OXYGEN SENSOR HEATER MONITOR
DESCRIPTIONÐIf there is an oxygen sensor
(O2S) DTC as well as a O2S heater DTC, the O2S
fault MUST be repaired first. After the O2S fault is
repaired, verify that the heater circuit is operating
correctly.
The voltage readings taken from the O2S are very
temperature sensitive. The readings are not accurate
below 300ÉC. Heating of the O2S is done to allow the
engine controller to shift to closed loop control as
soon as possible. The heating element used to heat
the O2S must be tested to ensure that it is heating
the sensor properly.
The heater element itself is not tested. The sensor
output is used to test the heater by isolating the
effect of the heater element on the O2S output volt-
age from the other effects. The resistance is normally
between 100 ohms and 4.5 megaohms. When oxygen
sensor temperature increases, the resistance in the
internal circuit decreases. The PCM sends a 5 volts
biased signal through the oxygen sensors to ground
this monitoring circuit. As the temperature increases,
resistance decreases and the PCM detects a lower
voltage at the reference signal. Inversely, as the tem-
perature decreases, the resistance increases and the
PCM detects a higher voltage at the reference signal.
The O2S circuit is monitored for a drop in voltage.
OPERATIONÐThe Oxygen Sensor Heater Moni-
tor begins after the ignition has been turned OFF
and the O2 sensors have cooled. The PCM sends a 5
volt bias to the oxygen sensor every 1.6 seconds. ThePCM keeps it biased for 35 ms each time. As the sen-
sor cools down, the resistance increases and the PCM
reads the increase in voltage. Once voltage has
increased to a predetermined amount, higher than
when the test started, the oxygen sensor is cool
enough to test heater operation.
When the oxygen sensor is cool enough, the PCM
energizes the ASD relay. Voltage to the O2 sensor
begins to increase the temperature. As the sensor
temperature increases, the internal resistance
decreases. The PCM continues biasing the 5 volt sig-
nal to the sensor. Each time the signal is biased, the
PCM reads a voltage decrease. When the PCM
detects a voltage decrease of a predetermined value
for several biased pulses, the test passes.
The heater elements are tested each time the
engine is turned OFF if all the enabling conditions
are met. If the monitor fails, the PCM stores a
maturing fault and a Freeze Frame is entered. If two
consecutive tests fail, a DTC is stored. Because the
ignition is OFF, the MIL is illuminated at the begin-
ning of the next key cycle.
Enabling ConditionsÐThe following conditions
must be met for the PCM to run the oxygen sensor
heater test:
²Engine run time of at least 5.1 minutes
²Key OFF power down
²Battery voltage of at least 10 volts
²Sufficient Oxygen Sensor cool down
Pending ConditionsÐThere are not conditions or
situations that prompt conflict or suspension of test-
ing. The oxygen sensor heater test is not run pending
resolution of MIL illumination due to oxygen sensor
failure.
SuspendÐThere are no conditions which exist for
suspending the Heater Monitor.
CATALYST MONITOR
To comply with clean air regulations, vehicles are
equipped with catalytic converters. These converters
reduce the emission of hydrocarbons, oxides of nitro-
gen and carbon monoxide.
Normal vehicle miles or engine misfire can cause a
catalyst to decay. A meltdown of the ceramic core can
cause a reduction of the exhaust passage. This can
increase vehicle emissions and deteriorate engine
performance, driveability and fuel economy.
The catalyst monitor uses dual oxygen sensors
(O2S's) to monitor the efficiency of the converter. The
dual O2S strategy is based on the fact that as a cat-
alyst deteriorates, its oxygen storage capacity and its
efficiency are both reduced. By monitoring the oxy-
gen storage capacity of a catalyst, its efficiency can
be indirectly calculated. The upstream O2S is used to
detect the amount of oxygen in the exhaust gas
before the gas enters the catalytic converter. The
RSEMISSIONS CONTROL25-3
EMISSIONS CONTROL (Continued)