ldp CHRYSLER VOYAGER 2004 Service Manual

SPECIAL TOOLS
BATTERY TEMPERATURE
SENSOR
DESCRIPTION
(NGC Vehicles) The PCM incorporates a Battery
Temperature Sensor (BTS) on its circuit board.
OPERATION
The PCM uses the temperature of the battery area
to control the charge system voltage. This tempera-
ture, along with data from monitored line voltage, is
used by the PCM to vary the battery charging rate.
The system voltage is higher at cold temperatures
and is gradually reduced as temperature around the
battery increases.
(NGC Vehicles) The ambient temperature sensor is
used to control the battery voltage based upon ambi-
ent temperature (approximation of battery tempera-
ture). The PCM maintains the optimal output of the
generator by monitoring battery voltage and control-
ling it to a range of 13.5 - 14.7 volts based on battery
temperature. The system target voltage is 13.5 ± 14.7
volts. However the actual voltage go below this dur-
ing heavy electrical loads and generator speeds. Also
the actual voltage can be lower than the target volt-
age between the battery and the battery voltage
sense circuit, approximately 0.2 Ð 0.3 volts.
The battery temperature sensor is also used for
OBD II diagnostics. Certain faults and OBD II mon-
itors are either enabled or disabled depending upon
the battery temperature sensor input (example: dis-
able purge and EGR, enable LDP). Most OBD II
monitors are disabled below 20ÉF.
REMOVAL
The battery temperature sensor is not serviced sep-
arately. If replacement is necessary, the PCM must
be replaced.
GENERATOR
DESCRIPTION
The generator is belt-driven by the engine. The
generator produces DC voltage at the B+ terminal. If
the generator is failed, the generator assembly sub-
components (generator and decoupler pulley) must be
inspected for individual failure and replaced accord-
ingly.
OPERATION
As the energized rotor begins to rotate within the
generator, the spinning magnetic field induces a cur-
rent into the windings of the stator coil. Once the
generator begins producing sufficient current, it also
provides the current needed to energize the rotor.
The Y type stator winding connections deliver the
induced AC current to 3 positive and 3 negative
diodes for rectification. From the diodes, rectified DC
current is delivered to the vehicles electrical system
through the generator, battery, and ground terminals.
Excessive or abnormal noise emitting from the gen-
erator may be caused by:
²Worn, loose or defective bearings
²Loose or defective drive pulley (2.4L) or decou-
pler (3.3/3.8L)
²Incorrect, worn, damaged or misadjusted drive
belt
²Loose mounting bolts
²Misaligned drive pulley
²Defective stator or diode
²Damaged internal fins
REMOVAL
REMOVAL - 2.4L
(1) Release hood latch and open hood.
(2) Disconnect battery negative cable.
(3) Disconnect the Inlet Air Temperature sensor.
(4) Remove the Air Box, refer to the Engine/Air
Cleaner for more information.
(5) Remove the EVAP Purge solenoid from its
bracket and reposition.
(6) Disconnect the push-in field wire connector
from back of generator.
(7) Remove nut holding B+ wire terminal to back
of generator.
(8) Separate B+ terminal from generator.
(9) Remove accessory drive belt, refer to the Cool-
ing System section for proper procedures.
(10) Remove the generator.
GENERATOR DECOUPLER 8433
RSCHARGING8F-23
CHARGING (Continued)

SPECIAL TOOLS
BATTERY TEMPERATURE
SENSOR
DESCRIPTION
(NGC Vehicles) The PCM incorporates a Battery
Temperature Sensor (BTS) on its circuit board.
OPERATION
The PCM uses the temperature of the battery area
to control the charge system voltage. This tempera-
ture, along with data from monitored line voltage, is
used by the PCM to vary the battery charging rate.
The system voltage is higher at cold temperatures
and is gradually reduced as temperature around the
battery increases. For vehicles with 1.6L engine, there is no physical
battery temp sensor in place to detect battery temp.
Rather, an algorithm buit in PCM is employed to pre-
dict battery temp using inlet air temp, vehicle speed,
and coolant temp, among other signals. The PCM
maintains the optimal output of the generator by
monitoring battery voltage and controlling it to a
range of 13.5 - 14.7 volts based on battery tempera-
ture. The system target voltage is 13.5 ± 14.7 volts.
However the actual voltage go below this during
heavy electrical loads and generator speeds. Also the
actual voltage can be lower than the target voltage
between the battery and the battery voltage sense
circuit, approximately 0.2 Ð 0.3 volts. The battery temperature sensor is also used for
OBD II diagnostics. Certain faults and OBD II mon-
itors are either enabled or disabled depending upon
the battery temperature sensor input (example: dis-
able purge and EGR, enable LDP). Most OBD II
monitors are disabled below 20ÉF.
REMOVAL
The battery temperature sensor is not serviced sep-
arately. If replacement is necessary, the PCM must
be replaced.
GENERATOR
DESCRIPTION
The generator is belt-driven by the engine. The
generator produces DC voltage at the B+ terminal. If
the generator is failed, the generator assembly sub-
components (generator and decoupler pulley) must be
inspected for individual failure and replaced accord-
ingly.
OPERATION
As the energized rotor begins to rotate within the
generator, the spinning magnetic field induces a cur-
rent into the windings of the stator coil. Once the
generator begins producing sufficient current, it also
provides the current needed to energize the rotor. The Y type stator winding connections deliver the
induced AC current to 3 positive and 3 negative
diodes for rectification. From the diodes, rectified DC
current is delivered to the vehicles electrical system
through the generator, battery, and ground terminals. Excessive or abnormal noise emitting from the gen-
erator may be caused by: ² Worn, loose or defective bearings
² Loose or defective drive pulley (2.4L) or decou-
pler (3.3/3.8L) ² Incorrect, worn, damaged or misadjusted drive
belt ² Loose mounting bolts
² Misaligned drive pulley
² Defective stator or diode
² Damaged internal fins
REMOVAL
REMOVAL - 2.4L
(1) Release hood latch and open hood.
(2) Disconnect battery negative cable.
(3) Disconnect the Inlet Air Temperature sensor.
(4) Remove the Air Box, refer to the Engine/Air
Cleaner for more information. (5) Remove the EVAP Purge solenoid from its
bracket and reposition. (6) Disconnect the push-in field wire connector
from back of generator. (7) Remove nut holding B+ wire terminal to back
of generator. (8) Separate B+ terminal from generator.
GENERATOR DECOUPLER 8433
RS CHARGING8Fs-23
CHARGING (Continued)

INTAKE MANIFOLD
DESCRIPTION
The intake manifold is a two piece aluminum cast-
ing (Fig. 101) that attaches to the cylinder head with
fasteners. The manifold is a long branch design to
enhance low and mid-range torque
DIAGNOSIS AND TESTING - INTAKE
MANIFOLD LEAKS
An intake manifold air leak is characterized by
lower than normal manifold vacuum. Also, one or
more cylinders may not be functioning.
WARNING: USE EXTREME CAUTION WHEN THE
ENGINE IS OPERATING. DO NOT STAND IN A
DIRECT LINE WITH THE FAN. DO NOT PUT YOUR
HANDS NEAR THE PULLEYS, BELTS OR THE FAN.
DO NOT WEAR LOOSE CLOTHING.
(1) Start the engine.
(2) Spray a small stream of water (Spray Bottle) at
the suspected leak area.
(3) If engine RPM'S change, the area of the sus-
pected leak has been found.
(4) Repair as required.
INTAKE MANIFOLD - UPPER
REMOVAL
(1) Disconnect negative cable from battery.
(2) Disconnect connector from inlet air tempera-
ture sensor (Fig. 102).
(3) Disconnect air intake tube at throttle body and
remove upper air cleaner housing.
(4) Disconnect connector from throttle position
sensor (TPS) (Fig. 104).
(5) Disconnect connector from idle air control (IAC)
motor (Fig. 104).
(6)
Disconnect connector from MAP sensor (Fig. 103).
(7) Remove vacuum lines for purge solenoid and
PCV valve at intake manifold.
(8) Remove vacuum lines for power brake booster,
LDP, EGR transducer, and speed control vacuum res-
ervoir (if equipped) at upper intake manifold fittings.
Fig. 101 Intake Manifold - Upper and Lower
1 - UPPER INTAKE MANIFOLD
2 - LOWER INTAKE MANIFOLD
Fig. 102 INLET AIR TEMPERATURE SENSOR - 2.4L
Fig. 103 MAP SENSOR - 2.4L
1 - MAP SENSOR
9 - 58 ENGINE 2.4LRS

(9) Disconnect throttle and speed control (if
equipped) cables from throttle lever and bracket.
(Refer to 14 - FUEL SYSTEM/FUEL INJECTION/
THROTTLE CONTROL CABLE - REMOVAL)
(10) Remove the EGR tube. (Refer to 25 - EMIS-
SIONS CONTROL/EXHAUST GAS RECIRCULA-
TION/TUBE - REMOVAL)
(11) Remove the upper manifold support bracket
bolt to manifold (Fig. 105).
(12) Remove engine oil dipstick from tube.
(13) Remove upper intake manifold bolts (Fig.
106). Remove upper intake manifold.
CAUTION: Cover intake manifold to prevent foreign
material from entering engine.
INSPECTION
(1) Check manifold surfaces for flatness with
straight edge. Surface must be flat within 0.15 mm
per 300 mm (0.006 in. per foot) of manifold length.
(2) Inspect manifold for cracks or distortion.
Replace manifold if necessary.
INSTALLATION
(1) Clean manifold sealing surfaces.
(2) Apply a 1.5 mm (0.060 in.) bead MopartGas-
ket Maker to the perimeter of the lower intake man-
ifold runner openings.
(3) Install upper intake manifold and tighten fas-
teners to 28 N´m (250 in. lbs.) in sequence shown in
(Fig. 106). Repeat this procedures until all fasteners
are at specified torque.
(4) Install engine oil dipstick.
(5) Install upper bolt in intake manifold to front
support bracket (Fig. 105). Torque to 28 N´m (250 in.
lbs.).
(6) Install EGR tube. (Refer to 25 - EMISSIONS
CONTROL/EXHAUST GAS RECIRCULATION/
TUBE - INSTALLATION)
(7) Install throttle cables in bracket.
(8) Connect throttle and speed control (if equipped)
cables to throttle lever.
(9) Connect vacuum lines for power brake booster,
LDP, EGR transducer, and speed control vacuum res-
ervoir (if equipped) at upper intake manifold fittings.
(10) Connect vacuum lines for purge solenoid and
PCV valve.
(11) Connect electrical connectors for MAP sensor,
throttle position sensor (TPS), and idle air control
(IAC) motor.
(12) Install air cleaner upper housing and air
intake tube to throttle body.
(13) Connect inlet air temperature sensor connec-
tor (Fig. 102).
(14) Connect negative cable to battery.
Fig. 104 Throttle Body Electrical Connectors -
Typical
1 - IDLE AIR CONTROL MOTOR CONNECTOR
2 - TPS CONNECTOR
Fig. 105 Upper Intake Manifold Support Bracket
1 - NUT - BRACKET TO CYLINDER HEAD COVER
2 - BOLT - BRACKET TO UPPER INTAKE MANIFOLD
3 - UPPER INTAKE MANIFOLD SUPPORT BRACKET
Fig. 106 Upper Intake Manifold Tightening Sequence
- 2.4L
RSENGINE 2.4L9-59
INTAKE MANIFOLD - UPPER (Continued)

DIAGNOSIS AND TESTING - INTAKE
MANIFOLD LEAKS
An intake manifold air leak is characterized by
lower than normal manifold vacuum. Also, one or
more cylinders may not be functioning.
WARNING: USE EXTREME CAUTION WHEN THE
ENGINE IS OPERATING. DO NOT STAND IN A
DIRECT LINE WITH THE FAN. DO NOT PUT YOUR
HANDS NEAR THE PULLEYS, BELTS OR THE FAN.
DO NOT WEAR LOOSE CLOTHING.
(1) Start the engine.
(2) Spray a small stream of water (Spray Bottle) at
the suspected leak area.
(3) If engine RPM'S change, the area of the sus-
pected leak has been found.
(4) Repair as required.
INTAKE MANIFOLD - UPPER
STANDARD PROCEDURE
STANDARD PROCEDURE - MANIFOLD
STRIPPED THREAD REPAIR
The composite upper intake manifold thread
bosses, if stripped out, can be repaired by utilizing a
repair screw available through Mopartparts. Repair
screws are available for the following manifold
attached components:
²MAP sensor
²Power steering reservoir
²EGR tube
²Throttle cable bracket
The repair screws require a unique tightening
torque specification from the original screw. Refer to
the following chart for specification.
DESCRIPTION TORQUE*
STRIP-OUT REPAIR SCREWS ONLY
MAP Sensor Repair
Screw4 N´m (35 in. lbs.)
Power Steering Reservoir
Repair Screw9 N´m (80 in. lbs.)
EGR Tube Attaching
Repair Screw9 N´m (80 in. lbs.)
Throttle Cable Bracket
Repair Screw9 N´m (80 in. lbs.)
*Install Slowly Using Hand Tools Only
STANDARD PROCEDURE - INTAKE MANIFOLD
VACUUM PORT REPAIR
The composite intake manifold vacuum ports can
be repaired. Although, if the manifold plenum cham-
ber is damaged or cracked, the manifold must be
replaced.
To repair a broken or damaged vacuum nipple
(port) on the composite intake manifold, perform the
following procedure:
PARTS REQUIRED TOOLS REQUIRED
´ Brass Nipple ± 1/49
O.D. x 1/89pipe thread
(LDP/Speed Control Port)´ Pipe Tap ± 1/89-18
NPT
´ Drill Bit ± 11/329
´ File/Sandpaper
´ Brass Nipple ± 1/29
O.D. x 1/49pipe thread
(Brake Booster Port)´ Pipe Tap ± 1/49-18
NPT
´ Drill Bit ± 7/169
´ File/Sandpaper
NOTE: While performing this procedure, avoid get-
ting the manifold material residue into the plenum
chamber.
(1) File or sand the remaining port back until a
flat surface is obtained (plane normal to nipple (port)
axis).
(2) Drill out the nipple (port) base using a 7/16º
(brake booster port) or 11/32º (LDP/speed control port
) drill bit (Fig. 113).
(3) Using a 1/4º±18 NPT (brake booster port) or
1/8º±18 NPT (LDP/speed control port ) pipe tap, cut
internal threads (Fig. 113). Use caution to start tap
in a axis same as original nipple.
(4) Apply MopartThread Sealant to threads of
repair nipple(s).
(5) Install repair nipple(s). Do not over torque
repair nipple(s).
REMOVAL - UPPER INTAKE MANIFOLD
(1) Disconnect battery negative cable.
(2) Disconnect inlet air temperature (IAT) sensor
electrical connector.
(3) Remove air inlet resonator to throttle body
hose assembly.
(4) Disconnect throttle and speed control cables
from throttle body (Refer to 14 - FUEL SYSTEM/
FUEL INJECTION/THROTTLE CONTROL CABLE -
REMOVAL).
(5) Disconnect make-up air hose support clip from
throttle cable bracket.
(6) Disconnect the automatic idle speed (AIS)
motor and throttle position sensor (TPS) wiring con-
nectors from throttle body.
RSENGINE 3.3/3.8L9 - 145
INTAKE MANIFOLD (Continued)

(7) Disconnect the manifold absolute pressure
(MAP) sensor electrical connector.
(8) Disconnect the vapor purge vacuum hose from
throttle body.
(9) Disconnect the PCV hose (Fig. 114).
(10) Remove the power steering reservoir attach-
ing bolts and only loosen the nut (Fig. 115). Lift res-
ervoir up to disengage lower mount from stud. Set
reservoir aside.Do notdisconnect hose.
(11) Disconnect the brake booster and leak detec-
tion pump (LDP) hoses from intake manifold (Fig.
116).
(12) Remove intake manifold bolts and remove the
manifold (Fig. 117).
(13) Cover the lower intake manifold with a suit-
able cover while the upper manifold is removed.
(14) Clean and inspect the upper intake manifold
(Refer to 9 - ENGINE/MANIFOLDS/INTAKE MANI-
FOLD - CLEANING) and (Refer to 9 - ENGINE/
MANIFOLDS/INTAKE MANIFOLD - INSPECTION).
CLEANING
(1) Discard gasket(s).
(2) Clean all sealing surfaces.
INSPECTION
Check manifold for:
²Damage and cracks.
Fig. 113 Intake Manifold Port Repair
1 - BRAKE BOOSTER PORT = 1/49±18 NPT PIPE TAP
1 - LDP/SPEED CONTROL PORT = 1/89±18 NPT PIPE TAP
2 - DRILL BIT = 7/169BRAKE BOOSTER PORT
2 - DRILL BIT = 11/329LDP/SPEED CONTROL PORT
3 - INTAKE MANIFOLD
Fig. 114 PCV & HOSE
1 - HOSE - PCV
2 - P C V VA LV E
Fig. 115 POWER STEERING FLUID RESERVOIR
1 - POWER STEERING RESERVOIR
2 - BOLT - RESERVOIR TO MANIFOLD
3 - NUT - RESERVOIR TO COIL BRACKET
9 - 146 ENGINE 3.3/3.8LRS
INTAKE MANIFOLD - UPPER (Continued)

²Mounting surface distortion by using a straight-
edge and thickness gauge.
INSTALLATION - UPPER INTAKE MANIFOLD
(1) If the following components were removed from
manifold, install and tighten to specifications:
CAUTION: The special screws used for the compos-
ite manifold attached components must be installed
slowly using hand tools only. This requirement is to
prevent the melting of material that causes stripped
threads. If threads become stripped, an oversize
repair screw is available. For more information and
procedure (Refer to 9 - ENGINE/MANIFOLDS/IN-
TAKE MANIFOLD - STANDARD PROCEDURE - MAN-
IFOLD STRIPPED THREAD REPAIR).
²MAP sensor - 1.7 N´m (15 in. lbs.)
²Throttle cable bracket - 5.6 N´m (50 in. lbs.)
(2) Remove covering on lower intake manifold and
clean surfaces.
(3) Inspect manifold gasket condition. Gaskets can
be re-used, if not damaged. To replace, remove gasket
from upper manifold (Fig. 117). Position new gasket
in seal channel and press lightly in-place. Repeat
procedure for each gasket position.
(4) Position upper manifold on lower manifold (Fig.
117). Apply MopartLock & Seal Adhesive (Medium
Strength Threadlocker) to each upper intake mani-
fold bolt. Install and tighten bolts to 12 N´m (105 in.
lbs.) following torque sequence in (Fig. 118).
(5) Connect the MAP sensor electrical connector.(6) Connect the brake booster and LDP vacuum
hose to intake manifold (Fig. 116).
Fig. 116 BRAKE BOOSTER & LDP VACUUM HOSES
1 - LDP & SPEED CONTROL VACUUM HOSE
2 - BRAKE BOOSTER VACUUM HOSE
3 - MAP SENSOR
Fig. 117 INTAKE MANIFOLD - UPPER
1 - BOLT
2 - MAP SENSOR
3 - SCREW
4 - MANIFOLD - UPPER
5 - WIRE HARNESS
6 - GASKET (3 PER CYL. BANK)
Fig. 118 UPPER MANIFOLD TIGHTENING
SEQUENCE
RSENGINE 3.3/3.8L9 - 147
INTAKE MANIFOLD - UPPER (Continued)

OPERATION
All models pass a full 360 degree rollover test
without fuel leakage. To accomplish this, fuel and
vapor flow controls are required for all fuel tank con-
nections.
All models are equipped with either one or two
check valves mounted into the top of the fuel tank (or
pump module).
An evaporation control system is connected to the
check valve(s)/control valve(Refer to 25 - EMIS-
SIONS CONTROL/EVAPORATIVE EMISSIONS/
ORVR - OPERATION) to reduce emissions of fuel
vapors into the atmosphere, when the tank is vented
due to vapor expansion in the tank. When fuel evap-
orates from the fuel tank, vapors pass through vent
hoses or tubes to a charcoal canister where they are
temporarily held. When the engine is running, the
vapors are drawn into the intake manifold. In addi-
tion, fuel vapors produced during vehicle refueling
are allowed to pass through the vent hoses/tubes to
the charcoal canister(s) for temporary storage (prior
to being drawn into the intake manifold). All models
are equipped with a self-diagnosing system using a
Leak Detection Pump (LDP) or Natural Vacuum
Leak Detection (NVLD). Refer to the Emission Con-
trol System for additional information.
INLET CHECK VALVE
All vehicles have an inlet check valve on the inside
of the fuel tank at the filler inlet
The valve prevents fuel from splashing back on
customer during vehicle refueling. The valve is a
non-serviceable item.
REMOVAL
(1) Remove fuel filler cap and perform Fuel Sys-
tem Pressure Release procedure (Fig. 14).
(2) Disconnect negative cable from battery.
(3) Insert fuel siphon hose into fuel filler neck and
push it into the tank.
(4) Drain fuel tank dry into holding tank or a
properly labeledGASOLINEsafety container.
(5) Raise vehicle on hoist and support.
(6) Use a transmission jack to support fuel tank.
Remove bolts from fuel tank straps.
(7) Lower tank slightly.
(8) Disconnect the fuel filler vent tube. Squeeze
tabs and pull apart (Fig. 15).
(9) Disconnect the fuel fill hose at the fuel tank
filler metal tubeNOT AT THE FUEL TANK(Fig.
15).
(10) Disconnect fuel line and vapor line at the
front of the fuel tank.
The fuel pump module electrical connector
has a retainer that locks it in place.(11) Slide fuel pump module electrical connector
lock to unlock.
(12) Push down on connector retainer (Fig. 16) and
pull connector off module.
(13) Lower tank from vehicle. Remove fuel filler
vent tube from frame (Fig. 17).
Fig. 14 Fuel Tank
1 - ROLLOVER VALVE
2 - FUEL FILLER INLET
3 - ROLLOVER VALVE
4 - FUEL PUMP MODULE
Fig. 15 FUEL FILLER AND VENT TUBE
1 - Filler Tube
2 - Vent Tube
RSFUEL DELIVERY14-11
FUEL TANK (Continued)

The following is a list of the monitored compo-
nents:
²Comprehensive Components
²Oxygen Sensor Monitor
²Oxygen Sensor Heater Monitor
²Catalyst Monitor
COMPREHENSIVE COMPONENTS
Along with the major monitors, OBD II requires
that the diagnostic system monitor any component
that could affect emissions levels. In many cases,
these components were being tested under OBD I.
The OBD I requirements focused mainly on testing
emissions-related components for electrical opens and
shorts.
However, OBD II also requires that inputs from
powertrain components to the PCM be tested for
rationality, and that outputs to powertrain compo-
nents from the PCM be tested forfunctionality.
Methods for monitoring the various Comprehensive
Component monitoring include:
(1) Circuit Continuity
²Open
²Shorted high
²Shorted to ground
(2) Rationality or Proper Functioning
²Inputs tested for rationality
²Outputs tested for functionality
NOTE: Comprehensive component monitors are
continuous. Therefore, enabling conditions do not
apply.
Input RationalityÐWhile input signals to the
PCM are constantly being monitored for electrical
opens and shorts, they are also tested for rationality.
This means that the input signal is compared against
other inputs and information to see if it makes sense
under the current conditions.
PCM sensor inputs that are checked for rationality
include:
²Manifold Absolute Pressure (MAP) Sensor
²Oxygen Sensor (O2S)
²Engine Coolant Temperature (ECT) Sensor
²Camshaft Position (CMP) Sensor
²Vehicle Speed Sensor
²Crankshaft Position (CKP) Sensor
²Intake/inlet Air Temperature (IAT) Sensor
²Throttle Position (TPS) Sensor
²Ambient Temperature Sensors
²Power Steering Switch
²Oxygen Sensor Heater
²Brake Switch
²Leak Detection Pump Switch or NVLD switch (if
equipped)
²P/N SwitchOutput FunctionalityÐPCM outputs are tested
for functionality in addition to testing for opens and
shorts. When the PCM provides a voltage to an out-
put component, it can verify that the command was
carried out by monitoring specific input signals for
expected changes. For example, when the PCM com-
mands the Idle Air Control (IAC) Motor to a specific
position under certain operating conditions, it expects
to see a specific (target) idle speed (RPM). If it does
not, it stores a DTC.
PCM outputs monitored for functionality include:
²Fuel Injectors
²Ignition Coils
²Idle Air Control
²Purge Solenoid
²EGR Solenoid (if equipped)
²LDP Solenoid or NVLD solenoid (if equipped)
²Radiator Fan Control
²Trans Controls
OXYGEN SENSOR (O2S) MONITOR
DESCRIPTIONÐEffective 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 operating temperature 300É to 350ÉC
(572É to 662ÉF), the sensor generates a voltage that
is inversely proportional to the amount of oxygen in
the exhaust. When there is a large amount of oxygen
in the exhaust caused by a lean condition, the sensor
produces a low voltage, below 450 mV. When the oxy-
gen content is lower, caused by a rich condition, the
sensor produces a higher voltage, above 450mV (volt-
ages are offset by 2.5 volts on NGC vehicles).
The information obtained by the sensor is used to
calculate the fuel injector pulse width. The PCM is
programmed to maintain the optimum air/fuel ratio.
At this mixture ratio, the catalyst works best to
remove hydrocarbons (HC), carbon monoxide (CO)
and nitrous oxide (NOx) from the exhaust.
The O2S is also the main sensing element for the
EGR (if equipped), Catalyst and Fuel Monitors.
The O2S may fail in any or all of the following
manners:
²Slow response rate (Big Slope)
²Reduced output voltage (Half Cycle)
²Heater Performance
Slow Response Rate (Big Slope)ÐResponse rate
is the time required for the sensor to switch from
lean to rich signal output once it is exposed to a
richer than optimum A/F mixture or vice versa. As
the PCM adjusts the air/fuel ratio, the sensor must
be able to rapidly detect the change. As the sensor
ages, it could take longer to detect the changes in the
oxygen content of the exhaust gas. The rate of
change that an oxygen sensor experiences is called
25 - 2 EMISSIONS CONTROLRS
EMISSIONS CONTROL (Continued)

NATURAL VAC LEAK
DETECTION ASSY
REMOVAL
(1) Disconnect thew negative battery cable.
(2) Raise vehicle and support (Fig. 4).
(3) Unlock and disconnect the electrical connector.
(4) Remove the hoses from the NVLD valve.
(5) Remove the 2 fasteners.
(6) Remove the valve and bracket from vehicle
(Fig. 5).
(7) Remove valve from bracket (Fig. 6).
INSTALLATION
(1) Install NVLD valve to the bracket (Fig. 6).
(2) Install valve and bracket to the vehicle (Fig. 5).
(3) Install the 2 mounting bolts and tighten.
(4) Install the electrical connector and lock.
(5) Install the 2 hoses and lock the clamps.
(6) Lower vehicle.
LEAK DETECTION PUMP
REMOVAL
(1) Disconnect the negative battery cable.
(2) Raise and support the vehicle.
(3) Remove 3 hoses (Fig. 7).
(4) Remove the electrical connector (Fig. 8).
(5) Remove the 3 screws and remove LDP pump.
INSTALLATION
(1) Install LDP.
(2) Install the 3 screws and tighten (Fig. 8).
(3) Install the electrical connector.
(4) Install the 3 hoses (Fig. 7).
(5) Lower vehicle.
(6) Connect the negative battery cable.
Fig. 4 NVLD LOCATION
Fig. 5 NVLD REMOVAL/INSTALLATION
Fig. 6 NVLD VALVE AND BRACKET
RSEVAPORATIVE EMISSIONS25-13