clock CHRYSLER CARAVAN 2002 Service Manual

GEARSHIFT MECHANISM
REMOVAL
(1) Disconnect battery negative cable.
(2) Remove gearshift knob by pushing down and
rotating
1¤4turn clock-wise (Fig. 185).
(3) Remove gearshift boot from center console by
disengaging at three (3) retaining clips (Fig. 186).(4) Apply park brake to allow park brake handle to
clear center console upon removal.
(5) Remove two (2) cupholder bottom plugs (Fig.
187).
(6) Remove four (4) center console-to-gearshift
mechanism screws. Remove console assembly (Fig.
188).
Fig. 185 Gearshift Knob Removal/Installation
1 - GEARSHIFT KNOB
2 - GEARSHIFT LEVER
Fig. 186 Gearshift Boot Removal/Installation
1 - GEARSHIFT BOOT
2 - CENTER CONSOLE
Fig. 187 Cup Holder Plugs
1 - CUPHOLDER PLUG (2)
Fig. 188 Center Console Removal/Installation (LHD
Shown Ð RHD Typical)
1 - CENTER CONSOLE
2 - SCREW (4)
3 - GEARSHIFT MECHANISM
RST850 MANUAL TRANSAXLE21 - 375
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(6) Install center console assembly (Fig. 201).
Install and torque center console-to-gearshift mecha-
nism screws to 5 N´m (45 in. lbs.).
(7) Install cupholder plugs (Fig. 202).(8) Install gearshift boot to console (Fig. 203).
Secure with three (3) retainer clips.
(9) Install gearshift knob to gearshift lever (Fig.
204). Orient shift pattern
1¤4-turn clockwise, push
down and rotate1¤4-turn counter-clockwise and
release. Secure boot to knob.
(10) Connect battery negative cable.
Fig. 201 Center Console Removal/Installation (LHD
Shown Ð RHD Typical)
1 - CENTER CONSOLE
2 - SCREW (4)
3 - GEARSHIFT MECHANISM
Fig. 202 Cup Holder Plugs
1 - CUPHOLDER PLUG (2)
Fig. 203 Gearshift Boot Removal/Installation
1 - GEARSHIFT BOOT
2 - CENTER CONSOLE
Fig. 204 Gearshift Knob Removal/Installation
1 - GEARSHIFT KNOB
2 - GEARSHIFT LEVER
RST850 MANUAL TRANSAXLE21 - 379
GEARSHIFT MECHANISM (Continued)
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Inspect for the following:
²Verify correct (OEM) wheel and tire, as well as
correct wheel weights. Aluminum wheels require
unique wheel weights. They are designed to fit the
contour of the wheel (Fig. 1).
²Inspect tires and wheels for damage, mud pack-
ing and unusual wear; correct as necessary.
²Check and adjust tire air pressure to the pres-
sure listed on the label attached to the rear face of
the driver's door.
ROAD TEST
Road test vehicle on a smooth road for a least five
miles to warm tires (remove any flat spots). Lightly
place hands on steering wheel at the 10:00 and 2:00
positions while slowly sweeping up and down from 90 to
110 km/h (55 to 70 mph) where legal speed limits allow.
Observe the steering wheel for:
²Visual Nibble (oscillation: clockwise/counter-
clockwise, usually due to tire imbalance)
²Visual Buzziness (high frequency, rapid vibra-
tion up and down)
To rule out vibrations due to brakes or powertrain:
²Lightly apply brakes at speed; if vibration occurs
or is enhanced, vibration is likely due to causes other
than tire and wheel assemblies.
²
Shift transmission into neutral while vibration is
occurring; if vibration is eliminated, vibration is likely
due to causes other than tire and wheel assemblies.
For brake vibrations, (Refer to 5 - BRAKES -
BASE/HYDRAULIC/MECHANICAL/ROTORS -
DIAGNOSIS AND TESTING).
For powertrain vibrations, (Refer to 3 - DIFFEREN-
TIAL & DRIVELINE - DIAGNOSIS AND TESTING).
For tire and wheel assembly vibrations, continue
with this diagnosis and testing procedure.
TIRE AND WHEEL BALANCE
(1) Balance the tire and wheel assemblies as nec-
essary following the wheel balancer manufacturer's
instructions and using the information listed in Stan-
dard Procedure - Tire And Wheel Balance. (Refer to
22 - TIRES/WHEELS - STANDARD PROCEDURE)
(2) Road test the vehicle for at least 5 miles, fol-
lowing the format described in Road Test.
(3) If the vibration persists, continue with this
diagnosis and testing procedure.
TIRE AND WHEEL RUNOUT/MATCH MOUNTING
(1)System Radial Runout.This on-the-vehicle
system check will measure the radial runout includ-
ing the hub, wheel and tire.
(a) Raise vehicle so tires clear floor. (Refer to
LUBRICATION & MAINTENANCE/HOISTING -
STANDARD PROCEDURE)
(b) Apply masking tape around the circumfer-
ence of the tire in the locations to be measured
(Fig. 2). Do not overlap the tape.
(c) Check system runout using Dial Indicator
Set, Special Tool C-3339A with 25-W wheel, or
equivalent. Place the end of the indicator against
each taped area (one at a time) (Fig. 2) and rotate
the tire and wheel. System radial runout should
not exceed 0.76 mm (0.030 inch) with no tread
ªdipsº or ªsteps.º Tread ªdipsº and ªstepsº can be
identified by spikes of the dial indicator gauge.
²Tread9dips9; Rapid decrease then increase in
dial indicator reading over 101.6 mm (4.0 inch) of
tread circumference.
²Tread9steps9; Rapid decrease or increase in dial
indicator reading over 101.6 mm (4.0 inch) of tread
circumference.
(d) If system runout is excessive, re-index the
tire and wheel assembly on the hub. Remove
assembly from vehicle and install it back on the
hub two studs over from original mounting posi-
tion. If re-indexing the tire and wheel assembly
corrects or reduces system runout, check hub
runout and repair as necessary (Refer to 5 -
BRAKES - BASE/HYDRAULIC/MECHANICAL/
ROTORS - DIAGNOSIS AND TESTING).
(e) If system runout is still excessive, continue
with this diagnosis and testing procedure.
(2)Tire and Wheel Assembly Radial Runout.
This radial runout check is performed with the tire
and wheel assembly off the vehicle.
(a) Remove tire and wheel assembly from vehicle
and install it on a suitable wheel balancer.
(b) Check system runout using Dial Indicator
Set, Special Tool C-3339A with 25-W wheel, or
equivalent. Place the end of the indicator against
each taped area (one at a time) (Fig. 2) and rotate
the tire and wheel. Radial runout should not
Fig. 1 Aluminum Wheel Weight
1 - TIRE
2 - WHEEL
3 - WHEEL WEIGHT
22 - 2 TIRES/WHEELSRS
TIRES/WHEELS (Continued)
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(3) Grasp the wheel cover at the edges in line with
the remaining installed wheel mounting nuts and
pull straight outward from the wheel. This will pop
the wheel cover retaining tabs over the two remain-
ing wheel nuts, removing the wheel cover from the
vehicle.
(4) Remove the two remaining wheel mounting
nuts from the hub's studs.
(5) Remove the wheel and tire from the hub.
INSTALLATION
INSTALLATION - TIRE AND WHEEL ASSEMBLY
(ALUMINUM WHEEL)
NOTE: Never use oil or grease on studs or wheel
mounting nuts.
(1) Position the tire and wheel assembly on the
wheel mounting studs using the hub pilot as a guide.
Place and hold the wheel flush up against the mount-
ing surface.
(2) Loosely install all 5 wheel mounting nuts.
Lightly snug the wheel nuts, then progressively
tighten them in the proper sequence (Fig. 13).
Tighten wheel mounting nuts to 135 N´m (100 ft.
lbs.).
(3) Lower the vehicle.
INSTALLATION - TIRE AND WHEEL ASSEMBLY
(STEEL WHEEL)
NOTE: Never use oil or grease on studs or wheel
mounting nuts.(1) Position the tire and wheel assembly on the
wheel mounting studs using the hub pilot as a guide.
Place and hold the wheel flush up against the mount-
ing surface.
NOTE: Wheel mounting nuts must be installed on
the studs as shown (Fig. 14) to allow proper instal-
lation of the wheel cover.
(2) Using the valve stem as an index placed at the
12 O'clock position, install andlightly tightentwo
wheel mounting nuts on the studs located at the 4
O'clock and 8 O'clock positions as shown (Fig. 14).
(3) Place the wheel cover on the wheel in the fol-
lowing fashion:
Fig. 12 NUTS SECURING WHEEL COVER
1 - VALVE STEM
2 - BOLT-ON WHEEL COVER
3 - NUTS SECURING WHEEL COVER
Fig. 13 Tightening Sequence
Fig. 14 TWO WHEEL MOUNTING NUTS INSTALLED
1 - WHEEL
2 - VALVE STEM
3 - HUB PILOT
4 - NUTS
22 - 8 TIRES/WHEELSRS
TIRES/WHEELS (Continued)
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CAUTION: Over-torquing the sensor nut by as little
as 12 N´m (106 in. lbs.) may result in sensor sepa-
ration from the valve stem. Under this condition,
the sensor may still function, however, the condi-
tion should be corrected immediately.(4) Mount tire on wheel following tire changer
manufacturers instructions, paying special attention
to the following to avoid damaging tire pressure sen-
sor:
(a) Rotating Wheel Tire Changers - Once the
wheel is mounted to the changer, position the sen-
sor valve stem approximately 210É from the head
of the changer in a clockwise direction before rotat-
ing the wheel (also in a clockwise direction) to
mount the tire (Fig. 20). Use this procedure on
both the upper and lower tire beads.
(b) Rotating Tool Tire Changers - Position the
wheel on the changer so that the sensor valve stem
is approximately 210É from the head of the changer
in a clockwise direction from the mounting end of
the tool (Fig. 21) Make sure the sensor is clear of
the lower bead breaker area to avoid damaging the
sensor when the breaker rises (Fig. 21). Rotate the
tool in a counterclockwise direction to mount the
tire. Use this procedure on both the upper and
lower tire beads.
(5) Install wheel and tire assembly on vehicle.
(Refer to 22 - TIRES/WHEELS - INSTALLATION)
Fig. 18 Start Mount/Dismount Tool Within 10
Degrees Of Valve Stem
Fig. 19 Sensor Mounting To Wheel
1 - TIRE PRESSURE SENSOR
2 - WHEEL
3 - NUT
Fig. 20 Mounting Tire Using Rotating Wheel
Machine
1 - HEAD OF CHANGER LOCATED HERE
2 - VALVE STEM
22 - 12 TIRES/WHEELSRS
SENSOR - TPM (Continued)
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(2) Fully open the sliding door.
(3) Verify that all center hinge bolts are tight.
(4) Adjust the rear of the sliding door up by turn-
ing the center hinge bolt clockwise (Fig. 13).
(5) Close the door and check the sliding door align-
ment.
(6) Adjust the front of the sliding door up by
adjusting lower hinge bolts.
(7) Open door half way and remove lower hinge
bolt access plug.
(8) Loosen bolts as necessary to move the front of
door up or down.
(9) Check the upper hinge for possible bind, adjust
as necessary.
(10) Close the door and check the sliding door
alignment.
(11) Fully open door and apply thread lock nut
onto the center hinge bolt. Tighten nut until till it
butts up against the welded nut on the center hinge.
Tighten nut to 15 N´m (130 in. lbs.). It may be nec-
essary to hold the center hinge bolt to prevent it
from turning while tightening nut.
(12) Verify alignment, adjust as necessary.
DOOR GAP ADJUSTMENT - FORE/AFT
(1) Check height of sliding door at the B-post and
C-post to determine which area is contributing the
greatest to the incorrect gaps.
(2) If the sliding door is high at the C-post;
(a) Open the door to mid-point of travel.
(b) Mark outline of center hinge on sliding door
to assist in making adjustments.
(c) Loosen center hinge bolts (Fig. 13).(d) Move hinge fore or aft to position the sliding
door into the correct location.
(e) Tighten center hinge bolts.
(f) Verify alignmen, adjust as necessary.
(3) If the sliding door is low at the B-post;
(a) Remove access plug in the sliding door trim
panel.
(b) Open the door to mid-point of travel.
(c) Mark outline of lower roller arm bracket on
sliding door to assist in making adjustments.
(d) Loosen lower roller arm bracket bolts (Fig.
14).
(e) Move hinge downward to raise the door.
(f) Tighten lower roller arm bracket bolts.
(g) Verify alignment, adjust as necessary.
(4) If the sliding door is low at the C-post;
(a) Open the door to mid-point of travel.
(b) Mark outline of center hinge on sliding door
to assist in making adjustments.
(c) Adjust the adjustment bolt up or down to
move the door position. (Fig. 13).
(d) Move hinge downward to raise the door.
(e) Tighten center hinge bolts.
(f) Verify alignment adjust as necessary.
(5) If the sliding door is high at the B-post;
(a) Remove access plug in the sliding door trim
panel.
(b) Open the door to mid-point of travel.
(c) Mark outline of lower roller arm bracket on
sliding door to assist in making adjustments.
(d) Loosen lower roller arm bracket bolts (Fig.
14).
(e) Move hinge upward to raise the door.
(f) Tighten lower roller arm bracket bolts.
(g) Verify alignment, adjust as necessary.
Fig. 13 SLIDING DOOR CENTER HINGE
1 - ADJUSTING BOLT
2 - WELD NUT
Fig. 14 SLIDING DOOR LOWER ROLLER ARM
1 - LOWER ROLLER ARM BRACKET
2 - BOLTS
2 - SLIDING DOOR
RSDOORS - SLIDING23-31
SLIDING DOOR (Continued)
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LUMBAR SUPPORT
REMOVAL
(1) Remove screw attaching lumbar handle to seat
back (Fig. 47).
(2) Remove seat back assembly from cushion.
(3) Detrim the seat back assembly.
(4) Remove frame and replace.
INSTALLATION
(1) Trim the seat back frame.
(2) Install seat back assembly to cushion.
(3) Install attaching screw to lumbar handle. The
handle is to be installed, between two and three
O'clock position. Tighten screw to 1 N´m (11 ft. lbs.)
torque.
(4) Test lumbar operation.
Fig. 47 LUMBAR HANDLE
1 - LUMBAR HANDLE
23 - 106 SEATSRS
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bezel with the snap clip receptacles on the retainer
above the headliner.
(7) Using hand pressure, press the top edge of the
rear heater-A/C control bezel upward until the two
snap clips are fully seated in their receptacles.
(8) Reconnect the battery negative cable.
(9) Using the DRB-IIItreset the Rear Tempera-
ture Selector calibration values.
(10) Verify that the Actuator Calibration of the
Front Control has passed. If an Actuator Calibration
has not passed correct any errors before proceeding
further.
(11) Rotate the Rear Temperature Selector counter
clockwise to the Cold Position, allow the Selector to
remain in the Cold Position for 5 seconds.
(12) Rotate the Rear Temperature Selector Clock-
wise to the Hot Position, allow the Selector to remain
in the Cold Position for 5 seconds.
(13) calibration is now complete.
BLEND DOOR ACTUATOR
DESCRIPTION
The blend door actuator is a reversible, 12-volt
Direct Current (DC), servo motor (Fig. 3). The single
blend door actuator is located on the outboard side of
the rear heater-A/C unit housing, below the mode
door actuator. The blend door actuator is mechani-
cally connected to the blend air door. The blend door
actuator is interchangeable with the actuator for the
mode door. Each actuator is contained within an
identical black molded plastic housing with an inte-gral wire connector receptacle. Two integral mount-
ing tabs allow the actuator to be secured with two
screws to the rear heater-A/C unit housing. Each
actuator also has an identical output shaft with
splines that connects it to the pivot or linkage of the
proper door. The blend door actuator does not require
mechanical indexing to the blend air door pivot, as it
is electronically calibrated by the front heater-A/C
control module. The blend door actuator cannot be
adjusted or repaired and, if damaged or faulty, it
must be replaced.
OPERATION
The blend door actuator is connected to the front
heater-A/C control module through the vehicle elec-
trical system by a dedicated two-wire take out and
connector of the rear HVAC wire harness. The blend
door actuator can move the blend air door in two
directions. When the front heater-A/C control module
pulls the voltage on one side of the motor connection
Fig. 2 Heater-A/C Control Bezel
1 - BEZEL
2 - SNAP CLIP (2)
3 - HEATER-A/C CONTROL
4 - SCREW (3)
5 - LOCATOR TAB (2)
Fig. 3 Blend Door Actuator
1 - SCREW (2)
2 - MODE DOOR ACTUATOR
3 - SCREW (2)
4 - CONNECTOR
5 - BLEND DOOR ACTUATOR
6 - CONNECTOR
24 - 30 CONTROLS - REARRS
A/C-HEATER CONTROL (Continued)
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CAUTION: All tools, including the refrigerant recy-
cling equipment, the manifold gauge set, and test
hoses should be kept clean and dry. Keep the work
area clean. Contamination of the refrigerant system
through careless work habits must be avoided. The
refrigerant system will remain chemically stable as
long as pure, moisture-free R-134a refrigerant and
refrigerant oil is used. Dirt, moisture, or air can
upset this chemical stability. Operational troubles
or serious damage can occur if foreign material is
introduced to the refrigerant system.
COMPRESSOR
DESCRIPTION
The compressor used on this vehicle can be one of
two models, depending upon the air conditioning sys-
tem in the vehicle. All vehicles use the Nippondenso
10S20 compressor. This compressor use an aluminum
swash plate, teflon coated pistons and aluminum
sleeveless cylinder walls. This compressor includes
an integral high pressure relief valve. The compres-
sor 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 cylin-
der block (3.3L and 3.8L engines) is integral to the
compressor. This compressor 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. The
refrigerant 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.
²Start the vehicle and run at idle.
²Turn the air conditioner On and listen for belt
squeal.
²If 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.
24 - 62 PLUMBING - FRONTRS
PLUMBING - FRONT (Continued)
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chemical reaction takes place. This means the con-
centration of oxygen will be the same downstream as
upstream. The output voltage of the downstream
O2S copies the voltage of the upstream sensor. The
only difference is a time lag (seen by the PCM)
between the switching of the O2S's.
To monitor the system, the number of lean-to-rich
switches of upstream and downstream O2S's is
counted. The ratio of downstream switches to
upstream switches is used to determine whether the
catalyst is operating properly. An effective catalyst
will have fewer downstream switches than it has
upstream switches i.e., a ratio closer to zero. For a
totally ineffective catalyst, this ratio will be one-to-
one, indicating that no oxidation occurs in the device.
The system must be monitored so that when cata-
lyst efficiency deteriorates and exhaust emissions
increase to over the legal limit, the MIL (Check
Engine lamp) will be illuminated.
LEAK DETECTION PUMP MONITOR (if equipped)
The leak detection assembly incorporates two pri-
mary functions: it must detect a leak in the evapora-
tive system and seal the evaporative system so the
leak detection test can be run.
The primary components within the assembly are:
A three port solenoid that activates both of the func-
tions listed above; a pump which contains a switch,
two check valves, a spring/diaphragm, and a canister
vent valve (CVV) seal which contains a spring loaded
vent seal valve.
Immediately after a cold start, between predeter-
mined temperature thresholds limits, the three port
solenoid is briefly energized. This initializes the
pump by drawing air into the pump cavity and also
closes the vent seal. During non test conditions the
vent seal is held open by the pump diaphragm
assembly which pushes it open at the full travel posi-
tion. The vent seal will remain closed while the
pump is cycling due to the reed switch triggering of
the three port solenoid that prevents the diaphragm
assembly from reaching full travel. After the brief
initialization period, the solenoid is de-energized
allowing atmospheric pressure to enter the pump
cavity, thus permitting the spring to drive the dia-
phragm which forces air out of the pump cavity and
into the vent system. When the solenoid is energized
and de energized, the cycle is repeated creating flow
in typical diaphragm pump fashion. The pump is con-
trolled in 2 modes:
Pump Mode:The pump is cycled at a fixed rate to
achieve a rapid pressure build in order to shorten the
overall test length.
Test Mode:The solenoid is energized with a fixed
duration pulse. Subsequent fixed pulses occur when
the diaphragm reaches the Switch closure point.The spring in the pump is set so that the system
will achieve an equalized pressure of about 7.5º
water. The cycle rate of pump strokes is quite rapid
as the system begins to pump up to this pressure. As
the pressure increases, the cycle rate starts to drop
off. If there is no leak in the system, the pump would
eventually stop pumping at the equalized pressure. If
there is a leak, it will continue to pump at a rate rep-
resentative of the flow characteristic of the size of the
leak. From this information we can determine if the
leak is larger than the required detection limit (cur-
rently set at .020º orifice by CARB). If a leak is
revealed during the leak test portion of the test, the
test is terminated at the end of the test mode and no
further system checks will be performed.
The canister vent valve will unseal the system
after completion of the test sequence as the pump
diaphragm assembly moves to the full travel position.
Evaporative system functionality will be verified by
using the stricter evap purge flow monitor. At an
appropriate warm idle the LDP will be energized to
seal the canister vent. The purge flow will be clocked
up from some small value in an attempt to see a
shift in the 02 control system. If fuel vapor, indicated
by a shift in the 02 control, is present the test is
passed. If not, it is assumed that the purge system is
not functioning in some respect. The LDP is again
turned off and the test is ended.
Natural Vacuum Leak Detection (NVLD) (if equipped)
The Natural Vacuum Leak Detection (NVLD) sys-
tem is the next generation evaporative leak detection
system that will first be used on vehicles equipped
with the Next Generation Controller (NGC) starting
in 2002 M.Y. This new system replaces the leak
detection pump as the method of evaporative system
leak detection. This is to detect a leak equivalent to a
0.0209(0.5 mm) hole. This system has the capability
to detect holes of this size very dependably.
The basic leak detection theory employed with
NVLD is the9Gas Law9. This is to say that the pres-
sure in a sealed vessel will change if the temperature
of the gas in the vessel changes. The vessel will only
see this effect if it is indeed sealed. Even small leaks
will allow the pressure in the vessel to come to equi-
librium with the ambient pressure. In addition to the
detection of very small leaks, this system has the
capability of detecting medium as well as large evap-
orative system leaks.
A vent valve seals the canister vent during engine
off conditions. If the vapor system has a leak of less
than the failure threshold, the evaporative system
will be pulled into a vacuum, either due to the cool
down from operating temperature or diurnal ambient
temperature cycling. The diurnal effect is considered
one of the primary contributors to the leak determi-
25 - 8 EMISSIONS CONTROLRS
EMISSIONS CONTROL (Continued)
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