2003 CHRYSLER CARAVAN clutch

pin-out and location views for the various wire har-
ness connectors, splices, and grounds.
DIAGNOSIS AND TESTING - COMPRESSOR
CLUTCH RELAY
The compressor clutch relay (Fig. 17) 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 compressor clutch relay identifi-
cation 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 75   5 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.
TERMINAL LEGEND
NUMBER IDENTIFICATION
30 COMMON FEED
85 COIL GROUND
86 COIL BATTERY
87 NORMALLY OPEN
87A NORMALLY CLOSED
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Unlatch and remove the cover from the Intelli-
gent Power Module (IPM).
(3) See the fuse and relay layout map molded into
the inner surface of the IPM cover for compressor
clutch relay identification and location.
(4) Remove the compressor clutch relay from the
IPM by pulling it straight up.
INSTALLATION
(1) See the fuse and relay layout map molded into
the inner surface of the Intelligent Power Module
(IPM) cover for compressor clutch relay identification
and location.
(2) Position the compressor clutch relay to the
proper receptacle in the IPM.
(3) Align the compressor clutch relay terminals
with the terminal cavities in the IPM relay recepta-
cle.
(4) Push down firmly on the compressor clutch
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.
EVAPORATOR TEMPERATURE
SENSOR
DESCRIPTION
Fig. 17 Compressor Clutch Relay
Fig. 18 Evaporator Temperature Sensor
1 - RIGHT FRONT STRUT TOWER
2 - EVAPORATOR TEMPERATURE SENSOR
3 - EXPANSION VALVE
4 - DASH PANEL
5 - RETAINER
24 - 22 CONTROLS - FRONTRS
COMPRESSOR CLUTCH RELAY (Continued)
ProCarManuals.com

The evaporator temperature sensor is a switch that
is installed on the top of the expansion valve in the
right rear corner of the engine compartment (Fig.
18). The sensor has a small probe that is inserted in
a small well in the body of the expansion valve that
is filled with a special silicone-based thermal grease.
A small molded plastic push-in retainer secures the
sensor to a threaded hole in the top surface of the
expansion valve. Two terminals within a molded
plastic connector receptacle on the sensor connect it
to the vehicle electrical system through a take out
and connector of the HVAC wire harness.
The evaporator temperature sensor cannot be
adjusted or repaired and, if faulty or damaged, it
must be replaced.
OPERATION
The evaporator temperature sensor monitors the
temperature of the evaporator through its connection
to the top of the expansion valve. The sensor will
change its internal resistance in response to the tem-
peratures it monitors. The heater-A/C control module
is connected to the sensor through a sensor ground
circuit and a sensor signal circuit. As the evaporator
temperature increases, the resistance of the sensor
decreases and the voltage monitored by the module
decreases. The module uses this monitored voltage
reading to an indication of the evaporator tempera-
ture. The heater-A/C control module is programmed
to respond to this input by sending electronic mes-
sages to the Powertrain Control Module (PCM) over
the Programmable Communications Interface (PCI)
data bus, and the PCM then cycles the air condition-
ing compressor clutch as necessary to optimize air
conditioning system performance and to protect the
system from evaporator freezing. The external loca-
tion of the sensor and the use of a screw allows the
sensor to be removed or installed from the expansion
valve without disturbing the refrigerant in the sys-
tem. The evaporator temperature sensor is diagnosed
using a DRBIIItscan tool. Refer to the appropriate
diagnostic information.
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Remove the air cleaner housing from the right
side of the engine compartment.
(3) Remove the windshield wiper assembly from
the vehicle(Refer to 8 - ELECTRICAL/WIPERS/
WASHERS/WIPER MODULE - REMOVAL).
(4) Remove the temperature sensor attaching
screw from the expansion valve.
(5) Pull the evaporator temperature sensor away
from the expansion valve far enough to access the
red release ring on the wiring connector. Push thered ring toward the connector to release lock and
remove the HVAC wire harness connector from the
temperature sensor.
(6) Remove the evaporator temperature sensor
from the engine compartment. Please note that any
grease removed with the old temperature sensor
must be replaced, failure to do so could result in poor
a/c performance.
INSTALLATION
(1) Position the evaporator temperature sensor
into the right rear corner of the engine compartment.
Please make sure any grease removed with the old
sensor has been replaced before the new sensor is
installed, failure to do so could lead to poor a/c per-
formance.
(2) Reconnect the HVAC wire harness connector
for the evaporator temperature sensor to the sensor
connector receptacle.
(3) Position the evaporator temperature sensor
onto the top of the expansion valve with the sensor
probe inserted into the well in the expansion valve.
(4) Install the temperature sensor retaining screw
and tighten.
(5) Install the window wiper assembly to the vehi-
cle(Refer to 8 - ELECTRICAL/WIPERS/WASHERS/
WIPER MODULE - INSTALLATION).
(6) Reinstall the air cleaner housing into the right
side of the engine compartment.
(7) Reconnect the battery negative cable.
(8) Run the HVAC Cool Down test to verify system
is operating properly(Refer to 24 - HEATING & AIR
CONDITIONING - DIAGNOSIS AND TESTING).
INFRARED TEMPERATURE
SENSOR
DESCRIPTION
The infrared temperature sensor consists of two
infrared transducers that are concealed behind a
clear lens located near the bottom of the center panel
outlet near the top of the instrument panel center
bezel (Fig. 19). These sensors are used only on mod-
els equipped with the optional Automatic Tempera-
ture Control (ATC) heating and air conditioning
system. A molded plastic connector receptacle on the
bottom of the panel outlet unit is concealed behind
the center bezel. A short, dedicated jumper wire har-
ness routed behind the center bezel connects the sen-
sors directly to the ATC heater-A/C control module
near the bottom of the center bezel. The infrared
temperature sensor is integral to the center bezel
panel outlet unit. The infrared sensors cannot be
adjusted or repaired and, if faulty or damaged, the
center bezel panel outlet unit must be replaced.
RSCONTROLS - FRONT24-23
EVAPORATOR TEMPERATURE SENSOR (Continued)
ProCarManuals.com

(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 mapmolded 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.
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-
Fig. 5 Blower Motor Relay
24 - 32 CONTROLS - REARRS
BLEND DOOR ACTUATOR (Continued)
ProCarManuals.com

A/C COMPRESSOR
DESCRIPTION
All vehicles use the Nippondenso 10S20 compres-
sor. This compressor use an aluminum swash plate,
teflon coated pistons and aluminum sleeveless cylin-
der walls. This compressor includes an integral high
pressure relief valve. The compressor is secured low
in the right front corner of the engine compartment
to a mounting bracket on the cylinder block (2.4L
engine), or directly to the cylinder block (3.3L and
3.8L engines) is integral to the compressor. This com-
pressor cannot be repaired. If faulty or damaged, the
entire compressor must be replaced. The compressor
clutch, pulley, and clutch coil are available for service
replacement.
OPERATION
The compressor is driven by the engine through an
electric clutch, drive pulley and belt arrangement.
The compressor is lubricated by refrigerant oil that is
circulated throughout the refrigerant system with the
refrigerant. The compressor draws in low-pressure
refrigerant vapor from the evaporator through its
suction port. It then compresses the refrigerant into
a high-pressure, high-temperature refrigerant vapor.
The compressor pumps high-pressure refrigerant
vapor to the condenser through the compressor dis-
charge port. The mechanical high pressure relief
valve is designed to vent refrigerant from the system
to protect against damage to the compressor or other
system components, caused by condenser air flow
restrictions or an overcharge of refrigerant. The valve
only vents enough refrigerant to reduce the system
pressure, then re-seats itself. The valve opens at a
discharge pressure of 3445 to 4135 kPA (500 to 600
psi) or above, and closes when a minimum discharge
pressure of 2756 kPa (400 psi) is reached.
DIAGNOSIS AND TESTING - COMPRESSOR
NOISE DIAGNOSIS
Excessive noise while the air conditioning compres-
sor is operating can be caused by loose compressor
mounts, a loose compressor clutch, or high operating
pressures in the refrigerant system. Verify compres-
sor drive belt condition, proper compressor mounting,
correct refrigerant charge level, and compressor head
pressure before compressor repair is performed.
With the close tolerances within the compressor, it
is possible to experience a temporary lockup. The
longer the compressor is inactive, the more likely the
condition is to occur. This condition is the result of
normal refrigerant migration within the refrigerant
system caused by ambient temperature changes. Therefrigerant migration may wash the refrigerant oil
out of the compressor.
NOTE: Prior to a vehicle being removed from ser-
vice or stored for more than two weeks, the com-
pressor should be operated to ensure adequate
refrigerant oil distribution throughout the system
components. Turn on the air conditioner for a min-
imum of five minutes with outside air and the high-
est blower speed selected.
BELT NOISE
If the compressor drive belt slips at initial start-up,
it does not necessarily mean the compressor has
failed. The following procedure can be used to iden-
tify a compressor drive belt noise problem.
A. Start the vehicle and run at idle.
B. Turn the air conditioner On and listen for belt
squeal.
C. If belt squeal is heard, turn the air conditioner
Off immediately.
If the belt squeal stops when the air conditioner is
turned Off, perform the following repair procedures.
(1) Using an appropriate sized oil filter wrench or
a strap wrench, grasp the outer diameter of the com-
pressor clutch hub. While facing the compressor,
rotate the hub clockwise, then counterclockwise. If
the hub rotates, proceed to the next step. If the hub
will not rotate, the compressor is internally damaged,
and must be replaced.
(2) Turn the hub clockwise five complete revolu-
tions and remove the tool.
(3) Start the vehicle and run at idle.
(4) Turn the air conditioner On. Observe the com-
pressor and the system for normal operation, noting
cooling performance and noise levels. Operate for five
minutes before turning the air conditioner Off. If
acceptable cooling performance is observed during
compressor operation, the compressor does not need
to be replaced.
(5) Inspect the drive belt for wear, damage, and
proper tension. (Refer to 7 - COOLING/ACCESSORY
DRIVE/DRIVE BELTS - DIAGNOSIS AND TEST-
ING).
RSPLUMBING - FRONT24-63
ProCarManuals.com

REMOVAL
REMOVAL - COMPRESSOR - 2.4/3.3/3.8L
ENGINES
WARNING: REFER TO THE APPLICABLE WARN-
INGS AND CAUTIONS FOR THIS SYSTEM BEFORE
PERFORMING THE FOLLOWING OPERATION.
(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING - FRONT - WARNING - A/C PLUMBING)
and (Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING - FRONT - CAUTION - A/C PLUMBING).
(1) Recover the refrigerant from the refrigerant
system. (Refer to 24 - HEATING & AIR CONDI-
TIONING/PLUMBING - FRONT/REFRIGERANT -
STANDARD PROCEDURE - REFRIGERANT
RECOVERY).
(2) Disconnect and isolate the battery negative
cable.
(3) Remove the nut that secures the suction line
fitting to the top of the compressor.
(4) Disconnect the suction line fitting from the
compressor suction port.
(5) Remove the seals from the suction line fitting
and discard.
(6) Install plugs in, or tape over the opened suc-
tion line fitting and the compressor suction port.
(7) Remove the nut that secures the discharge line
fitting to the top of the compressor.
(8) Disconnect the discharge line fitting from the
compressor discharge port.
(9) Remove the seals from the discharge line fit-
ting and discard.
(10) Install plugs in, or tape over the opened dis-
charge line fitting and the compressor discharge port.
(11) Raise and support the vehicle.
(12) Remove the serpentine accessory drive belt
from the front of the engine. (Refer to 7 - COOLING/
ACCESSORY DRIVE/DRIVE BELTS - 2.4L -
REMOVAL) or (Refer to 7 - COOLING/ACCESSORY
DRIVE/DRIVE BELTS - 3.3L/3.8L - REMOVAL).
(13) Disconnect the engine wire harness connector
for the compressor clutch coil from the coil pigtail
wire connector on the top of the compressor (Fig. 1)
or (Fig. 2).
(14) On models with the 3.3L and 3.8L engines,
disengage the retainer on the engine wire harness
compressor clutch coil take out from the bracket on
the top of the compressor.
(15) On models with the 2.4L engine, remove the
four screws that secure the compressor to the mount-
ing bracket on the engine.
(16) On models with the 3.3L and 3.8L engines,
remove the two screws and two nuts that secure the
compressor to the engine.(17) Remove the compressor from the engine com-
partment.
Fig. 1 Compressor - 2.4L Engine
1 - CLUTCH COIL CONNECTOR
2 - DISCHARGE PORT
3 - COMPRESSOR
4 - SUCTION PORT
5 - SCREW (4)
6 - COMPRESSOR MOUNTING BRACKET
Fig. 2 Compressor - 3.3L/3.8L Engine
1 - STUDS (2)
2 - CLUTCH COIL CONNECTOR
3 - DISCHARGE PORT
4 - SCREW (2)
5 - SUCTION PORT
6 - COMPRESSOR
7 - SCREW (IF EQUIPPED)
8 - NUTS (2)
24 - 64 PLUMBING - FRONTRS
A/C COMPRESSOR (Continued)
ProCarManuals.com

NOTE: If a replacement compressor is being
installed, be certain to drain and measure the refrig-
erant oil contained in the removed compressor.
This will determine how much oil the replacement
compressor must contain before it is installed.
(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING - FRONT/REFRIGERANT OIL - STAN-
DARD PROCEDURE - REFRIGERANT OIL LEVEL).
NOTE: The filter drier should always be replaced
when the compressor is replaced. This will remove
any contaminants including moisture from the sys-
tem.
REMOVAL - COMPRESSOR MOUNTING
BRACKET - 2.4L ENGINE
(1) Remove the compressor from the mounting
bracket. (Refer to 24 - HEATING & AIR CONDI-
TIONING/PLUMBING/COMPRESSOR - REMOVAL).
(2) Remove the four screws that secure the com-
pressor mounting bracket to the engine (Fig. 3).
(3) Remove the compressor mounting bracket from
the engine.
INSTALLATION
INSTALLATION - COMPRESSOR
NOTE: If a replacement compressor is being
installed, be certain to check the refrigerant oil
level. (Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING - FRONT/REFRIGERANT OIL - STAN-
DARD PROCEDURE - REFRIGERANT OIL LEVEL).Use only refrigerant oil of the type recommended
for the compressor in the vehicle.
NOTE: The filter drier should always be replaced
when the compressor is replaced. This will remove
any contaminants including moisture from the sys-
tem.
(1) Position the compressor into the engine com-
partment.
(2) On models with the 2.4L engine, loosely install
the four screws that secure the compressor to the
mounting bracket on the engine. Tighten the screws
to 28 N´m (21 ft. lbs.).
(3) On models with the 3.3L and 3.8L engines,
loosely install the two screws and two nuts that
secure the compressor to the engine. Tighten each of
the fasteners using the following sequence to 54 N´m
(40 ft. lbs.).
²The upper nut at the front of the compressor.
²The lower nut at the front of the compressor.
²The upper screw at the rear of the compressor.
²The lower screw at the rear of the compressor.
(4) On models with the 3.3L and 3.8L engines only,
engage the retainer on the engine wire harness com-
pressor clutch coil take out with the bracket on the
top of the compressor.
(5) Reconnect the engine wire harness connector
for the compressor clutch coil to the coil pigtail wire
connector on the top of the compressor.
(6) Reinstall the serpentine accessory drive belt
onto the front of the engine. (Refer to 7 - COOLING/
ACCESSORY DRIVE/DRIVE BELTS - 2.4L -
INSTALLATION) or (Refer to 7 - COOLING/ACCES-
SORY DRIVE/DRIVE BELTS - 3.3L/3.8L - INSTAL-
LATION).
(7) Lower the vehicle.
(8) Remove the tape or plugs from the compressor
discharge port and the discharge line fitting.
(9) Lubricate a new rubber O-ring seal with clean
refrigerant oil and install it on the discharge line fit-
ting.
(10) Install a new gasket and reconnect the dis-
charge line fitting to the compressor discharge port.
(11) Install and tighten the nut that secures the
discharge line fitting to the compressor. Tighten the
nut to 23 N´m (17 ft. lbs.).
(12) Remove the tape or plugs from the compressor
suction port and the suction line fitting.
(13) Lubricate a new rubber O-ring seal with clean
refrigerant oil and install it on the suction line fit-
ting.
(14) Install a new gasket and reconnect the suc-
tion line fitting to the compressor suction port.
(15) Install and tighten the nut that secures the
suction line fitting to the compressor. Tighten the nut
to 23 N´m (17 ft. lbs.).
Fig. 3 Compressor Mounting Bracket - 2.4L Engine
1 - MOUNTING BRACKET
2 - SCREWS (4)
3 - ENGINE
RSPLUMBING - FRONT24-65
A/C COMPRESSOR (Continued)
ProCarManuals.com

(4) Open both the suction and discharge valves,
then open the charge valve to allow the heated
refrigerant to flow into the system.
(5) When the transfer of refrigerant has stopped,
close both the suction and discharge valves.
(6) If all of the refrigerant charge did not transfer
from the dispensing device, open all of the windows
in the vehicle and set the heater-air conditioner con-
trols so that the compressor is engaged and the
blower motor is operating at its lowest speed setting.
Run the engine at a steady high idle (about 1400
rpm). If the compressor will not engage, test the com-
pressor clutch control circuit and repair as required.
(7) Open the suction valve to allow the remaining
refrigerant to transfer to the refrigerant system.
WARNING: TAKE CARE NOT TO OPEN THE DIS-
CHARGE (HIGH PRESSURE) VALVE AT THIS TIME.
(8) Close the suction valve and test the system
performance. (Refer to 24 - HEATING & AIR CON-
DITIONING - STANDARD PROCEDURE - A/C PER-
FORMANCE TEST).
(9) Disconnect the charging station and manifold
gauge set from the refrigerant system service ports.
(10) Reinstall the caps onto the refrigerant system
service ports.
(11) Run the HVAC Control Cooldown test to ver-
ify proper operation(Refer to 24 - HEATING & AIR
CONDITIONING - DIAGNOSIS AND TESTING).
STANDARD PROCEDURE - REFRIGERANT
SYSTEM EVACUATE
WARNING: REFER TO THE APPLICABLE WARN-
INGS AND CAUTIONS FOR THIS SYSTEM BEFORE
PERFORMING THE FOLLOWING OPERATION.
(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING - FRONT - WARNING - A/C PLUMBING)
and (Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING - FRONT - CAUTION - A/C PLUMBING).
If the refrigerant system has been open to the
atmosphere, it must be evacuated before the system
can be charged. If moisture and air enters the system
and becomes mixed with the refrigerant, the com-
pressor head pressure will rise above acceptable
operating levels. This will reduce the performance of
the air conditioner and damage the compressor.
Evacuating the refrigerant system will remove the
air and boil the moisture out of the system at near
room temperature. A R-134a refrigerant recovery/re-
cycling/charging station that meets SAE Standard
J2210 must be used to evacuate the refrigerant sys-
tem. See the operating instructions supplied by the
equipment manufacturer for proper care and use ofthis equipment. To evacuate the refrigerant system,
use the following procedure:
NOTE: When connecting the service equipment
couplings to the refrigerant system service ports,
be certain that the valve of each coupling is fully
closed. This will reduce the amount of effort
required to make the connection.
(1) Remove the caps from the refrigerant system
service ports and attach a manifold gauge set and a
R-134a refrigerant recovery/recycling/charging sta-
tion that meets SAE Standard J2210 to the refriger-
ant system.
(2) Open both the suction and discharge valves
and start the charging station vacuum pump.
(3) When the suction gauge has read 88 kPa (26
in. Hg.) vacuum or greater for 45 minutes, close both
the suction and discharge valves and turn off the
vacuum pump. If the refrigerant system fails to
reach the specified vacuum, the system has a leak
that must be corrected. (Refer to 24 - HEATING &
AIR CONDITIONING/PLUMBING - FRONT/RE-
FRIGERANT - STANDARD PROCEDURE -
REFRIGERANT SYSTEM LEAKS).
(4) If the refrigerant system maintains the speci-
fied vacuum for thirty minutes, restart the vacuum
pump, open both the suction and discharge valves,
and evacuate the system for an additional ten min-
utes.
(5) Close both the suction and discharge valves,
and turn off the charging station vacuum pump.
(6) The refrigerant system is now ready to be
charged with R-134a refrigerant. (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING -
FRONT/REFRIGERANT - STANDARD PROCE-
DURE - REFRIGERANT SYSTEM CHARGE).
STANDARD PROCEDURE - REFRIGERANT
RECOVERY
WARNING: REFER TO THE APPLICABLE WARN-
INGS AND CAUTIONS FOR THIS SYSTEM BEFORE
PERFORMING THE FOLLOWING OPERATION.
(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING - FRONT - WARNING - A/C PLUMBING)
and (Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING - FRONT - CAUTION - A/C PLUMBING).
A R-134a refrigerant recovery/recycling/charging
station that meets SAE Standard J2210 must be
used to recover the refrigerant from an R-134a refrig-
erant system, whenever the refrigerant system must
be opened for service. See the operating instructions
supplied by the equipment manufacturer for the
proper care and use of this equipment.
RSPLUMBING - FRONT24-89
REFRIGERANT (Continued)
ProCarManuals.com

ªBig Slopeº. The PCM checks the oxygen sensor volt-
age in increments of a few milliseconds.
Reduced Output Voltage (Half Cycle)ÐThe
output voltage of the O2S ranges from 0 to 1 volt
(voltages are offset by 2.5 volts on NGC vehicles). A
good sensor can easily generate any output voltage in
this range as it is exposed to different concentrations
of oxygen. To detect a shift in the A/F mixture (lean
or rich), the output voltage has to change beyond a
threshold value. A malfunctioning sensor could have
difficulty changing beyond the threshold value. Each
time the voltage signal surpasses the threshold, a
counter is incremented by one. This is called the Half
Cycle Counter.
Heater PerformanceÐThe heater is tested by a
separate monitor. Refer to the Oxygen Sensor Heater
Monitor.
OPERATIONÐAs the Oxygen Sensor signal
switches, the PCM monitors the half cycle and big
slope signals from the oxygen sensor. If during the
test neither counter reaches a predetermined value, a
malfunction is entered and Freeze Frame data is
stored. Only one counter reaching its predetermined
value is needed for the monitor to pass.
The Oxygen Sensor Monitor is a two trip monitor
that is tested only once per trip. When the Oxygen
Sensor fails the test in two consecutive trips, the
MIL is illuminated and a DTC is set. The MIL is
extinguished when the Oxygen Sensor monitor
passes in three consecutive trips. The DTC is erased
from memory after 40 consecutive warm-up cycles
without test failure.
Enabling ConditionsÐThe following conditions
must typically be met for the PCM to run the oxygen
sensor monitor:
²Battery voltage
²Engine temperature
²Engine run time
²Engine run time at a predetermined speed
²Engine run time at a predetermined speed and
throttle opening
²Transmission in gear and brake depressed (auto-
matic only)
²Fuel system in Closed Loop
²Long Term Adaptive (within parameters)
²Power Steering Switch in low PSI (no load)
²Engine at idle
²Fuel level above 15%
²Ambient air temperature
²Barometric pressure
²Engine RPM within acceptable range of desired
idle
Pending ConditionsÐThe Task Manager typi-
cally does not run the Oxygen Sensor Monitor if over-
lapping monitors are running or the MIL is
illuminated for any of the following:²Misfire Monitor
²Front Oxygen Sensor and Heater Monitor
²MAP Sensor
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 (if equipped)
²Intake/inlet 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
²Ethanol content learn is taking place and the
ethanol used once flag is set (if equipped)
SuspendÐThe Task Manager suspends maturing
a fault for the Oxygen Sensor Monitor if any of the
following 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 a sensor temperature of 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.
RSEMISSIONS CONTROL25-3
EMISSIONS CONTROL (Continued)
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