fuel cap CHRYSLER VOYAGER 2004 Owner's Manual

pressures may increase from 2 to 6 pounds per
square inch (psi) (14 to 41 kPa) during operation. Do
not reduce this normal pressure buildup.
Improper inflation can cause:
²Uneven wear patterns
²Reduced tread life
²Reduced fuel economy
²Unsatisfactory ride
²The vehicle to drift.
WARNING: OVER OR UNDER INFLATED TIRES CAN
AFFECT VEHICLE HANDLING. THE TIRE CAN FAIL
SUDDENLY, RESULTING IN LOSS OF VEHICLE
CONTROL.
Under inflation causes rapid shoulder wear, tire
flexing, and can result in tire failure (Fig. 25).
Over inflation causes rapid center wear and loss of
the tire's ability to cushion shocks (Fig. 26).STANDARD PROCEDURE - TIRE PRESSURE
FOR HIGH SPEED OPERATION
DaimlerChrysler Corporation advocates driving at
safe speeds within posted speed limits. Where speed
limits allow the vehicle to be driven at high speeds,
correct tire inflation pressure is very important.
Vehicles loaded to maximum capacity should not be
driven at continuous speeds over 120 km/h (75 mph).
Never exceed the maximum speed capacity of the
tire. For information on tire identification and speed
ratings, (Refer to 22 - TIRES/WHEELS/TIRES -
DESCRIPTION).
STANDARD PROCEDURE - TIRE LEAK
REPAIRING
For proper repairing, a radial tire must be removed
from the wheel. Repairs should only be made if the
defect, or puncture, is in the tread area (Fig. 27). The
tire should be replaced if the puncture is located in
the sidewall.
Deflate tire completely before attempting to dis-
mount the tire from the wheel.Use a lubricant
such as a mild soap solution when dismounting
or mounting tire.Use tools free of burrs or sharp
edges which could damage the tire or wheel rim.
Before mounting tire on wheel, make sure all rust
is removed from the rim bead and repaint if neces-
sary.
Install wheel on vehicle, and progressively tighten
the 5 wheel nuts to a torque of 135 N´m (100 ft. lbs.).
CLEANING - TIRES
Before delivery of a vehicle, remove the protective
coating on the tires with white sidewalls or raised
Fig. 25 Under Inflation Wear
1 - THIN TIRE TREAD AREAS
Fig. 26 Over Inflation Wear
1 - THIN TIRE TREAD AREA
Fig. 27 Tire Repair Area
1 - REPAIRABLE AREA
RSTIRES/WHEELS22-17
TIRES (Continued)

pressures may increase from 2 to 6 pounds per
square inch (psi) (14 to 41 kPa) during operation. Do
not reduce this normal pressure buildup.Improper inflation can cause:
² Uneven wear patterns
² Reduced tread life
² Reduced fuel economy
² Unsatisfactory ride
² The vehicle to drift.
WARNING: OVER OR UNDER INFLATED TIRES CAN
AFFECT VEHICLE HANDLING. THE TIRE CAN FAIL
SUDDENLY, RESULTING IN LOSS OF VEHICLE
CONTROL. Under inflation causes rapid shoulder wear, tire
flexing, and can result in tire failure (Fig. 4).
Over inflation causes rapid center wear and loss of
the tire's ability to cushion shocks (Fig. 5).STANDARD PROCEDURE - TIRE PRESSURE
FOR HIGH SPEED OPERATION
DaimlerChrysler Corporation advocates driving at
safe speeds within posted speed limits. Where speed
limits allow the vehicle to be driven at high speeds,
correct tire inflation pressure is very important.
Vehicles loaded to maximum capacity should not be
driven at continuous speeds over 120 km/h (75 mph).
Never exceed the maximum speed capacity of the
tire. For information on tire identification and speed
ratings, (Refer to 22 - TIRES/WHEELS/TIRES -
DESCRIPTION).
STANDARD PROCEDURE - TIRE LEAK
REPAIRING
For proper repairing, a radial tire must be removed
from the wheel. Repairs should only be made if the
defect, or puncture, is in the tread area (Fig. 6). The
tire should be replaced if the puncture is located in
the sidewall. Deflate tire completely before attempting to dis-
mount the tire from the wheel. Use a lubricant
such as a mild soap solution when dismounting
or mounting tire. Use tools free of burrs or sharp
edges which could damage the tire or wheel rim. Before mounting tire on wheel, make sure all rust
is removed from the rim bead and repaint if neces-
sary. Install wheel on vehicle, and progressively tighten
the 5 wheel nuts to a torque of 135 N´m (100 ft. lbs.).
Fig. 4 Under Inflation Wear
1 - THIN TIRE TREAD AREAS
Fig. 5 Over Inflation Wear
1 - THIN TIRE TREAD AREA
Fig. 6 Tire Repair Area
1 - REPAIRABLE AREA
RS TIRES22s-9
TIRES (Continued)

FUEL LINE
STANDARD PROCEDURE - CLEANING
(1) Remove the cabin heater fuel line (Refer to 24 -
HEATING & AIR CONDITIONING/CABIN HEAT-
ER/FUEL LINE - REMOVAL).
(2) With the cabin heater fuel line removed from
the vehicle, place a shop cloth on the fuel tank end of
the fuel line to catch any residue, then apply a small
amount of air pressure to the other end of the fuel
line.
(3) Check to see if air pressure is coming from the
tank end of the line. If pressure is flowing unre-
stricted the line is clean.
(4) If the fuel line shows any signs of being
restricted after air pressure is applied, the fuel line
should be replaced.
(5) Install the cabin heater fuel line (Refer to 24 -
HEATING & AIR CONDITIONING/CABIN HEAT-
ER/FUEL LINE - INSTALLATION).
(6) Verify function of the cabin heater.
REMOVAL
(1) Raise and support the vehicle. Take note of the
location of the flexible section of the cabin heater
exhaust tube.NOTE: Have an approved fuel holding device ready
to capture any diesel fuel that drains from the fuel
line or cabin heater unit.
(2) Remove clamps on dosing pump end of fuel line
and separate line from the pump (Fig. 5).
(3) Remove clamp from the fuel line at the fuel
tank connection and separate the line from the tank.
(4) Remove any retaining clips and remove the
fuel line from vehicle.
Fig. 5 Cabin Heater Dosing Pump Fuel Line
1 - FUEL LINE
2 - RETAINING CLAMP3 - DOSING PUMP
4 - HEATER AIR INTAKE PIPE
RSCABIN HEATER24 - 117

INSTALLATION
WARNING: DO NOT OPERATE THE DIESEL SUP-
PLEMENTAL CABIN HEATER IN AN ENCLOSED
AREA SUCH AS A GARAGE THAT DOES NOT HAVE
EXHAUST VENTILATION FACILITIES. ALWAYS VENT
THE CABIN HEATER EXHAUST WHEN OPERATING
THE CABIN HEATER. ALLOW THE DIESEL SUPPLE-
MENTAL CABIN HEATER TO COOL BEFORE PER-
FORMING ANY SERVICE PROCEDURES TO THE
CABIN HEATER. VERIFY THAT ALL DIESEL SUP-
PLEMENTAL CABIN HEATER FUEL LINES ARE
SECURELY FASTENED TO THEIR RESPECTIVE
COMPONENTS BEFORE PERFORMING ANY SER-
VICE PROCEDURES TO THE CABIN HEATER. FAIL-
URE TO FOLLOW THESE INSTRUCTION MAY
RESULT IN PERSONAL INJURY OR DEATH.
NOTE: Verify that there is more than 1/8 of a tank of
fuel in the vehicle's fuel tank before performing this
procedure. Add fuel, if necessary.
(1) Install the cabin heater fuel supply line into
vehicle and fuel line retainers.
(2) Install the fuel line connection at the fuel tank
and tighten the connection securely.
(3) Install the fuel line at the dosing pump and
tighten the connection securely.
(4) Lower the vehicle.
NOTE: Failure to prime the dosing pump after drain-
ing the supplemental cabin fuel line will prevent
cabin heater activation during the first attempt to
start the cabin heater. This will also set a diagnostic
trouble code (DTC) in the cabin heater control's
memory. Do not perform the Dosing Pump Priming
procedure if an attempt was made to start the cabin
heater without priming the dosing pump first. This
will put excess fuel in the cabin heater and cause
smoke to emit from the cabin heater exhaust pipe
when cabin heater activation occurs.
(5) Connect the DRBIIItscan tool to the diagnos-
tic link connector.
(6) Turn the ignition to the ON position.
NOTE: Do not activate the dosing pump prime more
than one time. This will put excess fuel in the sup-
plemental cabin heater and cause smoke to emit
from the cabin heater exhaust pipe when cabin
heater activation occurs.
NOTE: A clicking noise heard coming from the dos-
ing pump indicates that the pump is operational.(7) With the DRBIIItscan tool in Cabin Heater,
select System Tests and Dosing Pump Prime. Allow
the dosing pump to run for the full 45 second cycle
time. When the 45 second cycle is complete, press
Page Back on the DRBIIItscan tool key pad to exit
the Dosing Pump Prime. The Dosing Pump Priming
procedure is now complete.
HEATER UNIT
REMOVAL
WARNING: DO NOT OPERATE THE DIESEL SUP-
PLEMENTAL CABIN HEATER IN AN ENCLOSED
AREA SUCH AS A GARAGE THAT DOES NOT HAVE
EXHAUST VENTILATION FACILITIES. ALWAYS VENT
THE CABIN HEATER EXHAUST WHEN OPERATING
THE CABIN HEATER. ALLOW THE DIESEL SUPPLE-
MENTAL CABIN HEATER TO COOL BEFORE PER-
FORMING ANY SERVICE PROCEDURES TO THE
CABIN HEATER. VERIFY THAT ALL DIESEL SUP-
PLEMENTAL CABIN HEATER FUEL LINES ARE
SECURELY FASTENED TO THEIR RESPECTIVE
COMPONENTS BEFORE PERFORMING ANY SER-
VICE PROCEDURES TO THE CABIN HEATER. FAIL-
URE TO FOLLOW THESE INSTRUCTION MAY
RESULT IN PERSONAL INJURY OR DEATH.
(1) Raise and support the vehicle. Take note of the
location of the flexible section of the cabin heater
exhaust tube.
(2) Drain the engine cooling system (Refer to 7 -
COOLING - STANDARD PROCEDURE).
(3) Carefully open one hose to the underbody tube
assembly and drain the remaining coolant. A salvage
hose is a good idea to control the residual coolant, as
flow will occur from both the cabin heater and the
hose and tube assemblies.
(4) Remove the second hose from the underbody
hose and tube assembly.
(5) Loosen the hose and tube assembly from the
toe-board crossmember at two locations.
(6) Disconnect the electrical connector from the
body harness near the toe-board crossmember and
rail.
(7) Remove the wiring harness from the toe-board
crossmember (Refer to 24 - HEATING & AIR CON-
DITIONING/CABIN HEATER/HEATER UNIT -
REMOVAL).
(8) Open the fuel filler cap. Disconnect the rubber
fuel hose between the body tube assembly and the
fuel pump nipple at the body tube joint. A minimal
amount of fuel may flow from the open port.
NOTE: Utilize an approved fuel storage container to
catch any residual fuel.
24 - 118 CABIN HEATERRS
FUEL LINE (Continued)

(9) Loosen the two fasteners at the rail. Take care
to notice that the exhaust tube bracket tab is on top
of the heater bracket and that there are two spacer
washers installed between the rubber grommets.
(10) Remove the flexible section of the cabin
heater exhaust tube from the exhaust tube by loos-
ening the clamp. Remove the hose from the exhaust
tube. Removal of the rail tube assembly may aid in
this service operation (Refer to 24 - HEATING & AIR
CONDITIONING/CABIN HEATER/EXHAUST TUBE
- REMOVAL).
(11) Remove seat hex nut at the heater mounting
flange to crossmember.
(12) Loosen the remaining fasteners which mount
the exhaust tube assembly to the vehicle.
(a) Install a suitable support device under the
cabin heater and secure the cabin heater to the
support.
(13) Loosen the remaining three fasteners to the
crossmembers.
(14) Remove the loosened fasteners that support
the cabin heater while supporting the weight of the
heater.
(15) Swing the cabin heater mounting bracket
from between the exhaust bracket and rail mounting
location. Drain any residual coolant from the cabin
heater.
(16) Remove the cabin heater from the vehicle.
INSTALLATION
(1) Install the cabin heater mounting bracket
between the exhaust bracket and the rail mounting
location.
(2) Support the cabin heater and install the fasten-
ers that secure the cabin heater to the mounting
bracket.
(3) Install the three fasteners to the crossmem-
bers. Tighten the M6 fasteners to 7 N´m (62 in. lbs.).
(4) Position the two spacer washers between the
body and the rubber grommets for the two mounting
points on the rail.
(5) Tighten the remaining M6 fasteners to 7 N´m
(62 in. lbs.) and the M8 fasteners to 23 N´m (17 ft.
lbs.) which mount the exhaust tube assembly to the
vehicle.
(6) Install the seat hex nut at the heater mounting
flange to the crossmembers. Tighten the nut to 60
N´m (44 ft. lbs.)
(7) Install the flexible section of the cabin heater
exhaust tube to the exhaust tube. Tighten the M6
bolt of the clamp securley. Install the hose to the
exhaust tube.
(8) Tighten the two M8 fasteners at the rail to 23
N´m (17 ft. lbs.). Taking care so that the exhaust
tube bracket tab is on the top of the heater bracket.(9) Install the wiring harness (Refer to 24 - HEAT-
ING & AIR CONDITIONING/CABIN HEATER/
HEATER UNIT - INSTALLATION).
(10) Tighten the hose and tube assembly to the
toe-board crossmember at two locations.
(11) Install the second hose to the underbody hose
and tube assembly.
(12) Connect the rubber fuel hose between the
body tube assembly and the fuel pump nipple at the
body tube joint. Close the fuel fill cap.
(13) Remove the cabin heater support device from
under the vehicle.
(14) Lower the vehicle.
(15) Fill the engine cooling system (Refer to 7 -
COOLING - STANDARD PROCEDURE).
(16) Verify function of the cabin heater.
SUPPLEMENTAL DIESEL
HEATER WIRING
REMOVAL
(1) Elevate vehicle on a lift taking note of the
exhaust tube flexible section.
(2) Unplug connector from vehicle wiring harness
to cabin heater harness.
(3) Unplug connector from cabin heater harness to
dosing pump connector.
(4) Unplug two connectors from cabin heater har-
ness to cabin heater controller connectors.
(5) Remove two wiring harness connectors from
underbody.
(6) Remove two wiring harness connectors from
cabin heater shield.
(7) Carefully route the cabin heater harness to the
left side between the cabin heater unit and the cabin
heater shield.
INSTALLATION
(1) Carefully route the cabin heater harness from
the left side of the cabin heater between the cabin
heater unit and the cabin heater shield.
(2) Install the two wiring harness retaining con-
nectors to the cabin heater shield.
(3) Route the wiring harness along the underside
of the vehicle and install the two wiring harness
retaining connectors.
(4) Plug the two connectors from the cabin heater
harness to the cabin heater controller.
(5) Plug the connector to the cabin heater harness
to the dosing pump connector.
(6) Plug the connector from the vehicle wiring har-
ness to the cabin heater harness.
(7) Lower the vehicle.
(8) Verify function of the cabin heater.
RSCABIN HEATER24 - 119
HEATER UNIT (Continued)

OPERATIONÐThe Oxygen Sensor Heater Moni-
tor begins after the ignition has been turned OFF.
The PCM sends a 5 volt bias to the oxygen sensor
every 1.6 seconds. The PCM keeps it biased for 35
ms each time. As the sensor cools down, the resis-
tance increases and the PCM reads the increase in
voltage. Once voltage has increased to a predeter-
mined amount, higher than when the test started,
the oxygen sensor is cool enough to test heater oper-
ation.
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 3 minutes
²Engine run time at a predetermined speed
and throttle opening.
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
PCM calculates the A/F mixture from the output of
the O2S. A low voltage indicates high oxygen content
(lean mixture). A high voltage indicates a low content
of oxygen (rich mixture).
When the upstream O2S detects a lean condition,
there is an abundance of oxygen in the exhaust gas.
A functioning converter would store this oxygen so it
can use it for the oxidation of HC and CO. As the
converter absorbs the oxygen, there will be a lack of
oxygen downstream of the converter. The output of
the downstream O2S will indicate limited activity in
this condition.
As the converter loses the ability to store oxygen,
the condition can be detected from the behavior of
the downstream O2S. When the efficiency drops, no
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.
Monitor OperationÐTo monitor catalyst effi-
ciency, the PCM expands the rich and lean switch
points of the heated oxygen sensor. With extended
switch points, the air/fuel mixture runs richer and
leaner to overburden the catalytic converter. Once
the test is started, the air/fuel mixture runs rich and
lean and the O2 switches are counted. A switch is
counted when an oxygen sensor signal goes from
below the lean threshold to above the rich threshold.
The number of Rear O2 sensor switches is divided by
the number of Front O2 sensor switches to determine
the switching ratio.
The test runs for 20 seconds. As catalyst efficiency
deteriorated over the life of the vehicle, the switch
rate at the downstream sensor approaches that of the
upstream sensor. If at any point during the test
25 - 4 EMISSIONS CONTROLRS
EMISSIONS CONTROL (Continued)

Effective control of exhaust emissions is achieved
by an oxygen feedback system. The most important
element of the feedback system is the O2S. The O2S
is located in the exhaust path. Once it reaches oper-
ating temperatures of 300É to 350ÉC (572 É to 662ÉF),
the sensor generates a voltage that is inversely pro-
portional to the amount of oxygen in the exhaust.
The information obtained by the sensor is used to
calculate the fuel injector pulse width. This main-
tains a 14.7 to 1 Air Fuel (A/F) ratio. At this mixture
ratio, the catalyst works best to remove hydrocarbons
(HC), carbon monoxide (CO) and nitrogen oxide
(NOx) from the exhaust.
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 O2S circuit is monitored for a drop in voltage.
The sensor output is used to test the heater by iso-
lating the effect of the heater element on the O2S
output voltage from the other effects.
EGR MONITOR (if equipped)
The Powertrain Control Module (PCM) performs
an on-board diagnostic check of the EGR system.
The EGR monitor is used to test whether the EGR
system is operating within specifications. The diag-
nostic check activates only during selected engine/
driving conditions. When the conditions are met, the
EGR is turned off (solenoid energized) and the O2S
compensation control is monitored. Turning off the
EGR shifts the air fuel (A/F) ratio in the lean direc-
tion. The O2S data should indicate an increase in the
O2 concentration in the combustion chamber when
the exhaust gases are no longer recirculated. While
this test does not directly measure the operation of
the EGR system, it can be inferred from the shift in
the O2S data whether the EGR system is operating
correctly. Because the O2S is being used, the O2S
test must pass its test before the EGR test. Also
looks at EGR linear potentiometer for feedback.
MISFIRE MONITOR
Excessive engine misfire results in increased cata-
lyst temperature and causes an increase in HC emis-
sions. Severe misfires could cause catalyst damage.
To prevent catalytic convertor damage, the PCM
monitors engine misfire.
The Powertrain Control Module (PCM) monitors
for misfire during most engine operating conditions
(positive torque) by looking at changes in the crank-
shaft speed. If a misfire occurs the speed of the
crankshaft will vary more than normal.FUEL SYSTEM 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. The catalyst works best
when the air fuel (A/F) ratio is at or near the opti-
mum of 14.7 to 1.
The PCM is programmed to maintain the optimum
air/fuel ratio. This is done by making short term cor-
rections in the fuel injector pulse width based on the
O2S output. The programmed memory acts as a self
calibration tool that the engine controller uses to
compensate for variations in engine specifications,
sensor tolerances and engine fatigue over the life
span of the engine. By monitoring the actual air-fuel
ratio with the O2S (short term) and multiplying that
with the program long-term (adaptive) memory and
comparing that to the limit, it can be determined
whether it will pass an emissions test. If a malfunc-
tion occurs such that the PCM cannot maintain the
optimum A/F ratio, then the MIL will be illuminated.
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's 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
PCM calculates the A/F mixture from the output of
the O2S. A low voltage indicates high oxygen content
(lean mixture). A high voltage indicates a low content
of oxygen (rich mixture).
When the upstream O2S detects a lean condition,
there is an abundance of oxygen in the exhaust gas.
A functioning converter would store this oxygen so it
can use it for the oxidation of HC and CO. As the
converter absorbs the oxygen, there will be a lack of
oxygen downstream of the converter. The output of
the downstream O2S will indicate limited activity in
this condition.
As the converter loses the ability to store oxygen,
the condition can be detected from the behavior of
the downstream O2S. When the efficiency drops, no
RSEMISSIONS CONTROL25-7
EMISSIONS CONTROL (Continued)

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.
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). 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.
The NVLD seals the canister vent during engine off
conditions. If the EVAP 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 tem-
perature cycling. The diurnal effect is considered one
of the primary contributors to the leak determination
by this diagnostic. When the vacuum in the system
exceeds about 19H2O (0.25 KPA), a vacuum switch
closes. The switch closure sends a signal to the NGC.
The NGC, via appropriate logic strategies (described
below), utilizes the switch signal, or lack thereof, to
make a determination of whether a leak is present.
The NVLD device is designed with a normally open
vacuum switch, a normally closed solenoid, and a
seal, which is actuated by both the solenoid and a
diaphragm. The NVLD is located on the atmosphericvent side of the canister. The NVLD assembly may
be mounted on top of the canister outlet, or in-line
between the canister and atmospheric vent filter. The
normally open vacuum switch will close with about 19
H2O (0.25 KPA) vacuum in the evaporative system.
The diaphragm actuates the switch. This is above the
opening point of the fuel inlet check valve in the fill
tube so cap off leaks can be detected. Submerged fill
systems must have recirculation lines that do not
have the in-line normally closed check valve that pro-
tects the system from failed nozzle liquid ingestion,
in order to detect cap off conditions.
The normally closed valve in the NVLD is intended
to maintain the seal on the evaporative system dur-
ing the engine off condition. If vacuum in the evapo-
rative system exceeds 39to 69H2O (0.75 to 1.5 KPA),
the valve will be pulled off the seat, opening the seal.
This will protect the system from excessive vacuum
as well as allowing sufficient purge flow in the event
that the solenoid was to become inoperative.
The solenoid actuates the valve to unseal the can-
ister vent while the engine is running. It also will be
used to close the vent during the medium and large
leak tests and during the purge flow check. This sole-
noid requires initial 1.5 amps of current to pull the
valve open but after 100 ms. will be duty cycled down
to an average of about 150 mA for the remainder of
the drive cycle.
Another feature in the device is a diaphragm that
will open the seal in the NVLD with pressure in the
evaporative system. The device will9blow off9at
about 0.59H2O (0.12 KPA) pressure to permit the
venting of vapors during refueling. An added benefit
to this is that it will also allow the tank to9breathe9
during increasing temperatures, thus limiting the
pressure in the tank to this low level. This is benefi-
cial because the induced vacuum during a subse-
quent declining temperature will achieve the switch
closed (pass threshold) sooner than if the tank had to
decay from a built up pressure.
The device itself has 3 wires: Switch sense, sole-
noid driver and ground. It also includes a resistor to
protect the switch from a short to battery or a short
to ground. The NGC utilizes a high-side driver to
energize and duty-cycle the solenoid.
DESCRIPTION - HIGH AND LOW LIMITS
The PCM compares input signal voltages from each
input device with established high and low limits for
the device. If the input voltage is not within limits
and other criteria are met, the PCM stores a diagnos-
tic trouble code in memory. Other diagnostic trouble
code criteria might include engine RPM limits or
input voltages from other sensors or switches that
must be present before verifying a diagnostic trouble
code condition.
25 - 8 EMISSIONS CONTROLRS
EMISSIONS CONTROL (Continued)

EVAPORATIVE EMISSIONS
TABLE OF CONTENTS
page page
EVAPORATIVE EMISSIONS
OPERATION - EVAPORATION CONTROL
SYSTEM............................10
SPECIFICATIONS
TORQUE............................11
EVAP/PURGE SOLENOID
DESCRIPTION.........................12
OPERATION...........................12
REMOVAL.............................12
INSTALLATION.........................12
FUEL FILLER CAP
DESCRIPTION.........................12
OPERATION...........................12
NATURAL VAC LEAK DETECTION ASSY
REMOVAL.............................13
INSTALLATION.........................13
LEAK DETECTION PUMP
REMOVAL.............................13
INSTALLATION.........................13ORVR
OPERATION...........................14
DIAGNOSIS AND TESTING - VEHICLE DOES
NOT FILL............................16
P C V VA LV E
DESCRIPTION.........................16
OPERATION...........................16
DIAGNOSIS AND TESTING - PCV SYSTEM . . . 17
VAPOR CANISTER
DESCRIPTION.........................18
OPERATION...........................18
REMOVAL
REMOVAL...........................18
REMOVAL - WITH NVLD................19
REMOVAL - REAR EVAP CANISTER.......19
INSTALLATION
INSTALLATION.......................19
INSTALLATION - WITH NVLD............20
INSTALLATION - REAR EVAP CANISTER . . . 20
EVAPORATIVE EMISSIONS
OPERATION - EVAPORATION CONTROL
SYSTEM
The evaporation control system prevents the emis-
sion of fuel tank vapors into the atmosphere. When
fuel evaporates in the fuel tank, the vapors pass
through vent hoses or tubes to an activated carbon
filled evaporative canister. The canister temporarily
holds the vapors. The Powertrain Control Module
(PCM) allows intake manifold vacuum to draw
vapors into the combustion chambers during certain
operating conditions (Fig. 1).All engines use a proportional purge solenoid sys-
tem. The PCM controls vapor flow by operating the
purge solenoid. Refer to Proportional Purge Solenoid
in this section.
NOTE: The evaporative system uses specially man-
ufactured hoses. If they need replacement, only use
fuel resistant hose. Also the hoses must be able to
pass an Ozone compliance test.
NOTE: For more information on Onboard Refueling
Vapor Recovery (ORVR), refer to the Fuel Delivery
section.
25 - 10 EVAPORATIVE EMISSIONSRS

SPECIFICATIONS
TORQUE
DESCRIPTION N´m Ft. Lbs. In. Lbs.
PCV VAlve 3.3/3.8L 6.3 55
Fig. 1 ORVR System Schematic
1 - FUEL TANK (PLASTIC)
2 - FUEL FILLER TUBE
3 - FUEL CAP (PRESSURE/RELIEF)
4 - FILL TUBE TO FUEL TANK CONNECTOR (ELASTOMERIC)
5 - TANK VENT/ROLLOVER VALVE(S)
6 - VAPOR RECIRCULATION LINE
7 - TANK VAPOR LINE
8 - VAPOR LINE TO CANISTER
9 - CHECK VALVE (N/C)
10 - CONTROL VALVE
11 - NATURAL VACUUM LEAD DETECTION (NVLD)12 - LIQUID SEPARATOR (IF EQUIPPED)
13 - ENGINE WIRING HARNESS TO NVLD
14 - VAPOR CANISTER
15 - PURGE LINE
16 - PURGE DEVICE
17 - WITHOUT NVLD
18 - BREATHER ELEMENT
19 - FLOW CONTROL ORIFICE
20 - SERVICE PORT
21 - WITH NVLD
RSEVAPORATIVE EMISSIONS25-11
EVAPORATIVE EMISSIONS (Continued)