fuel cap CHRYSLER VOYAGER 2004 User Guide

SPECIAL TOOLS
EXHAUST SYSTEM
CATALYTIC CONVERTER
DESCRIPTION
The toe board three-way catalytic converter is con-
nected to the exhaust manifold by the use of flex
joint and a gasket. The outlet connects to the muffler
inlet pipe and is secured with a band type clamp
(Fig. 1).
The exhaust flex-joint coupling (Fig. 3) is used to
secure the catalytic converter to the exhaust manifold.
The flex-joint has four bolts, four flag nuts and a gas-
ket that are separate parts from the exhaust flex-joint.
The flex-joint is welded to the catalytic converter.
CAUTION: When servicing, care must be exercised
not to dent or bend the bellows or bellows cover of
the flex-joint. Should this occur, the flex-joint will
eventually fail and require the catalytic converter be
replaced.
OPERATION
The three-way catalytic converter simultaneously
converts three exhaust emissions into harmless
gases. Specifically, HC and CO emissions are con-
verted into water (H2O) and carbon dioxide (CO2).
Oxides of Nitrogen (NOx) are converted into elemen-
tal Nitrogen (N) and water. The three-way catalyst is
most efficient in converting HC, CO and NOx at the
stoichiometric air fuel ratio of 14.7:1.
The oxygen content in a catalyst is important for
efficient conversion of exhaust gases. When a high
oxygen content (lean) air/fuel ratio is present for an
extended period, oxygen content in a catalyst can
reach a maximum. When a rich air/fuel ratio is
present for an extended period, the oxygen content in
the catalyst can become totally depleted. When this
occurs, the catalyst fails to convert the gases. This is
known as catalyst9punch through.9
Catalyst operation is dependent on its ability to
store and release the oxygen needed to complete the
emissions-reducing chemical reactions. As a catalyst
deteriorates, its ability to store oxygen is reduced.
Since the catalyst's ability to store oxygen is some-
what related to proper operation, oxygen storage can
be used as an indicator of catalyst performance.
Refer to the appropriate Diagnostic Information for
diagnosis of a catalyst related Diagnostic Trouble
Code (DTC).
Back Pressure Test Adapter - CH8519
Pressure Transducer CH7063
DRB III & PEP Module - OT-CH6010A
Fig. 3 Flex-joint
1 - FLANGE
2 - END CAPS
3 - CATALYTIC CONVERTER
4 - FLEXIBLE BELLOWS
11 - 4 EXHAUST SYSTEMRS
EXHAUST SYSTEM (Continued)

FUEL DELIVERY
DESCRIPTION
The front wheel drive car uses a plastic fuel tank
located rear center of the vehicle.
The Fuel Delivery System consists of: the following
items:
²Electric fuel pump module
²Fuel filter
²Tubes/lines/hoses
²Fuel injectors
The in-tank fuel pump module contains the fuel
pump. The pump is serviced as part of the fuel pump
module. Refer to Fuel Pump Module.
The fuel filter is replaceable only as part of the
fuel pump module.
OPERATION
The fuel system provides fuel pressure by an
in-tank pump module. The Powertrain Control Mod-
ule (PCM) controls the operation of the fuel system
by providing battery voltage to the fuel pump
through the fuel pump relay. The PCM requires only
three inputs and a good ground to operate the fuel
pump relay. The three inputs are:
²Ignition voltage
²Crankshaft Position (CKP) sensor
²Camshaft Position (CMP) sensor
DIAGNOSIS AND TESTING - FUEL DELIVERY
SYSTEM
(Refer to Appropriate Diagnostic Information)
STANDARD PROCEDURE
STANDARD PROCEDURE - FUEL SYSTEM
PRESSURE RELEASE PROCEDURE
(1) Remove Fuel Pump relay from Power Distribu-
tion Center (PDC). For location of relay, refer to label
on underside of PDC cover.
(2) Start and run engine until it stalls.
(3) Attempt restarting engine until it will no
longer run.
(4) Turn ignition key to OFF position.
(5) Return fuel pump relay to PDC.
(6) One or more Diagnostic Trouble Codes (DTC's)
may have been stored in PCM memory due to fuel
pump relay removal. The DRB IIItscan tool must be
used to erase a DTC.
STANDARD PROCEDURE - DRAINING FUEL
TANK
Two different procedures may be used to drain fuel
tank (lowering tank or using DRBIIItscan tool).The quickest draining procedure involves lowering
the fuel tank.
WARNING: RELEASE FUEL SYSTEM PRESSURE
BEFORE SERVICING FUEL SYSTEM COMPONENTS.
SERVICE VEHICLES IN WELL VENTILATED AREAS
AND AVOID IGNITION SOURCES. NEVER SMOKE
WHILE SERVICING THE VEHICLE. THIS MAY
RESULT IN PERSONAL INJURY OR DEATH.
As an alternative procedure, the electric fuel pump
may be activated allowing tank to be drained at fuel
rail connection. Refer to DRBIIItscan tool for fuel
pump activation procedures. Before disconnecting
fuel line at fuel rail, release fuel pressure. Refer to
the Fuel System Pressure Release Procedure in this
group for procedures. Disconnect the fuel line at the
fuel rail and remove the plastic retainer from the
fuel rail. Take plastic retainer and install it back into
the fuel line from body. Check the O-ring and make
sure that it is in place and not damaged. Attach end
of special test hose tool number 6539 at fuel line con-
nection from the body line. Position opposite end of
this hose tool to an approved gasoline draining sta-
tion. Activate fuel pump and drain tank until empty.
When done remove the special test hose tool number
6539 from the body line. Remove the plastic retainer
from the special test hose tool number 6539 and rein-
stall it into the fuel line from the body. Check the
O-ring and make sure that it is in place and not
damaged. Install the fuel line to the fuel rail.
If electric fuel pump is not operating, tank must be
lowered for fuel draining. Refer to following proce-
dures.
(1) Remove fuel filler cap.
(2) Perform the Fuel System Pressure Release pro-
cedure.
(3) Disconnect negative cable from battery.
(4) Raise vehicle and support.
(5) Certain models are equipped with a separate
grounding wire (strap) connecting the fuel fill tube
assembly to the body. Disconnect wire by removing
screw.
(6) Open fuel fill door and remove screws mount-
ing fuel filler tube assembly to body. Do not discon-
nect rubber fuel fill or vent hoses from tank at this
time.
(7) Place a transmission jack under center of fuel
tank. Apply a slight amount of pressure to fuel tank
with transmission jack.
(8) Remove fuel tank mounting straps.
(9)Lower the tank just enough so that the
filler tube fitting is the highest point of the fuel
tank.
(10) Remove filler tube from fuel tank. Tank will
be drained through this fitting.
14 - 2 FUEL DELIVERYRS

FUEL LEVEL SENDING UNIT /
SENSOR
DESCRIPTION
The fuel gauge level sending unit is attached to the
side of fuel pump module. The level sensor is a vari-
able resistor.
OPERATION
Its resistance changes with the amount of fuel in
the tank. The float arm attached to the sensor moves
as the fuel level changes.
The fuel level input is used as an input for OBD II.
If the fuel level is below 15% or above 85% of total
tank capacity several monitors are disabled. There
are diagnostics for the level circuit open and shorted.
REMOVAL
Remove fuel pump module. Refer to Fuel Pump
Module in this section.
(1) Depress retaining tab and remove the fuel
pump/level sensor connector from theBOTTOMof
the fuel pump module electrical connector (Fig. 1).
NOTE: The pump module harness on TOP of flange
is not serviceable or removable.
(2) Pull off the locking wedge.
(3) Using a small screwdriver lift locking finger
away from terminal and push terminal out of connec-
tor (Fig. 2).
(4) Push level sensor signal and ground terminals
out of the connector (Fig. 3).(5) Insert a screwdriver between the fuel pump
module and the top of the level sensor housing (Fig.
4). Push level sensor down slightly.
(6) Slide level sensor wires through opening fuel
pump module (Fig. 5).
(7) Slide level sensor out of installation channel in
module.
INSTALLATION
(1) Insert level sensor wires into bottom of opening
in module.
(2) Wrap wires into groove in back of level sensor
(Fig. 6).
(3) While feeding wires into guide grooves, slide
level sensor up into channel until it snaps into place
(Fig. 7). Ensure tab at bottom of sensor locks in
place.
Fig. 1 Fuel Pump/Level Sensor Electrical Connector
1 - ELECTRICAL CONNECTOR
2 - RETAINING TAB
Fig. 2 Wire Terminal Locking Finger
1 - LOCKING FINGER
2 - WIRE TERMINAL
Fig. 3 Removing Wires From
1 - FUEL PUMP FEED (RED B+)
2 - LEVEL SENSOR SIGNAL
3 - LEVEL SENSOR GROUND
4 - FUEL PUMP GROUND (BK)
RSFUEL DELIVERY14-5

FUEL PUMP
DESCRIPTION
The electric fuel pump is located in and is part of
the fuel pump module. It is a positive displacement,
gerotor type, immersible pump with a permanent
magnet electric motor. The fuel pump module is sus-
pended in fuel in the fuel tank.
OPERATION
The pump draws fuel through a strainer and
pushes it through the motor to the outlet. The pump
contains a check valve. The valve, in the pump out-
let, maintains pump pressure during engine off con-
ditions, for a short while. It is normal for fuel
pressure to drop to zero after cooldown. The fuel
pump relay provides voltage to the fuel pump. The
fuel pump has a maximum deadheaded pressure out-
put of approximately 880 kPa (130 psi). The regula-
tor adjusts fuel system pressure to approximately
400 kpa  34 kpa (58 psi   5 psi).
FUEL PUMP MODULE
DESCRIPTION
The fuel pump module is installed in the top of the
fuel tank (Fig. 9).
The fuel pump module contains the following:
²Electric fuel pump²Fuel pump reservoir
²Inlet strainer
²Fuel pressure regulator
²Fuel gauge sending unit
²Fuel supply line connection
The inlet strainer, fuel pressure regulator
and fuel level sensor are the only serviceable
items. If the fuel pump or electrical wiring har-
ness requires service, replace the fuel pump
module.
The electric fuel pump is located in and is part of
the fuel pump module. It is a positive displacement,
gerotor type, immersible pump with a permanent
magnet electric motor.
OPERATION
The pump draws fuel through a strainer and
pushes it through the motor to the outlet. The pump
contains one check valve. The check valve, in the
pump outlet, maintains pump pressure during engine
off conditions. The fuel pump relay provides voltage
to the fuel pump.
The fuel pump has a maximum deadheaded pres-
sure output of approximately 880 kPa (130 psi). The
regulator adjusts fuel system pressure to approxi-
mately 400  34 kPa (58  5 psi).
FUEL PUMP ELECTRICAL CONTROL
Voltage to operate the electric pump is supplied
through the fuel pump relay. For an electrical opera-
tional description of the fuel pump refer to fuel Pump
RelayÐPCM Output.
ELECTRICAL PUMP REPLACEMENT
The electric fuel pump is not serviceable. If the
fuel pump or electrical wiring harness needs replace-
ment, the complete fuel pump module must be
replaced. Perform the Fuel System Pressure Release
procedure before servicing the fuel pump.
REMOVAL
WARNING: RELEASE FUEL SYSTEM PRESSURE
BEFORE SERVICING FUEL SYSTEM COMPONENTS.
SERVICE VEHICLES IN WELL VENTILATED AREAS
AND AVOID IGNITION SOURCES. NEVER SMOKE
WHILE SERVICING THE VEHICLE.
(1) Remove fuel filler cap and perform Fuel Sys-
tem Pressure Release procedure.
(2) Disconnect negative cable from auxiliary
jumper terminal.
(3) Drain fuel tank, refer to the Fuel Tank proce-
dure in the Fuel Delivery section.
(4) Remove fuel tank, refer to the Fuel Tank
removal section.
Fig. 9 Fuel Pump Module
1 - INLET STRAINER
2 - FUEL RESERVOIR
3 - FUEL PRESSURE REGULATOR
4 - FUEL LEVEL SENSOR
5 - FILTER
6 - GROUND STRAPS
14 - 8 FUEL DELIVERYRS

(5) Clean top of tank to remove loose dirt and
debris.
(6) Using a brass punch and hammer remove lock-
nut to release pump module (Fig. 10).
WARNING: THE FUEL RESERVOIR OF THE FUEL
PUMP MODULE DOES NOT EMPTY OUT WHEN THE
TANK IS DRAINED. THE FUEL IN THE RESERVOIR
MAY SPILL OUT WHEN THE MODULE IS REMOVED.
(7) Remove fuel pump module and O-ring from
tank (Fig. 11). Discard O-ring.
INSTALLATION
NOTE: Be careful not to allow dirt/debris to fall into
the fuel tank.
(1) Wipe seal area of tank clean and place a new
O-ring seal in position on pump.
(2) Position fuel pump module in tank.
(3) Tighten lockring using a brass punch and ham-
mer to install the lockring (Fig. 10).
(4) Install fuel tank, refer to the Fuel Tank instal-
lation section.
(5) Lower vehicle.
(6) Connect negative cable battery.
(7) Fill fuel tank. Use the DRB IIItscan tool to
pressurize the fuel system. Check for leaks.
(8) Install fuel filler cap.
FUEL RAIL
REMOVAL
REMOVAL - 2.4L
(1) Perform fuel system pressure release procedure
before servicing or starting repairs.Refer to
Fuel System Pressure Release Procedure in this sec-
tion.
(2) Disconnect negative cable from battery.
(3) Disconnect the wiring connectors for fuel injec-
tors harness (Fig. 12).
(4) Remove wiring harness from brackets.
(5) Disconnect the connectors from the fuel injec-
tors.
Fig. 10 FUEL PUMP MODULE LOCKING RING
Fig. 11 Fuel Pump Module Removal
1 - FUEL PUMP MODULE
2 - O-RING
Fig. 12 FUEL RAIL AND INJECTORS 2.4L
1 - Fuel Injectors
2 - Fuel Rail
RSFUEL DELIVERY14-9
FUEL PUMP MODULE (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)

INSTALLATION
(1) Position fuel tank on transmission jack. Con-
nect check valve hose. Connect fuel filler tube vent
hose to fuel filler tube.
(2) Feed filler vent line thru frame rail.
(3) Raise tank into position and carefully work fuel
filler metal tube into the rubber hose on fuel tank. A
light coating of clean engine oil on the tube end may
be used to aid assembly.
(4) Tighten strap bolts to 54 N´m (40 ft. lbs.)
torque. Tighten T strap bolt to 28.2 N´m (250 in.
lbs.). Remove transmission jack.
(5) Tighten filler hose clamp to 3.3 N´m (30 in.
lbs.).CAUTION: Ensure straps are not twisted or bent
before or after tightening strap screws.
(6) Connect fuel pump/module electrical connector.
Place retainer in locked position.
(7) Lubricate the fuel supply line with clean 30
weight engine oil, install the quick connect fuel fit-
ting. Refer to Tube/Fitting Assembly in the Fuel
Delivery section of this section.
(8) Connect the control vapor lines at front of
tank.
(9) Pull-pull-push on all connections to make sure
of connection.
(10) Fill fuel tank, replace cap, and connect bat-
tery negative cable.
(11) Use the DRBIIItscan tool to pressurize the
fuel system. Check for leaks.
FUEL TANK FILLER TUBE
REMOVAL
(1) Disconnect the negative battery cable.
(2) Remove the 3 screws at the filler door.
(3) Raise and support vehicle
(4) Remove the left rear tire.
(5) Remove the splash shield (Fig. 19) or (Fig. 18).
(6)For RGRemove the canister from filler tube
(Fig. 20).
(7)For RGDisconnect the vent at the top of the
filler tube.
(8) Remove the ground strap.
(9) Remove filler tube at tank.
Fig. 16 Pump Module Connector Retainer and Lock
1 - PUSH DOWN ON RETAINER
2 - CONNECTOR LOCK
Fig. 17 VENT HOSE
Fig. 18 FUEL FILLER TUBE (RS)
14 - 12 FUEL DELIVERYRS
FUEL TANK (Continued)

and is determined by the PCM processing all the
data previously discussed to obtain the optimum
injector pulse width for each operating condition. The
pulse width is controlled by the duration of the
ground path provided.
REMOVAL
REMOVAL - 2.4L
The fuel rail must be removed first (Fig. 12). Refer
to Fuel Rail Removal in this section.
(1) Disconnect injector wiring connector from injec-
tor.
(2) Position fuel rail assembly so that the fuel
injectors are easily accessible (Fig. 13).(3) Rotate injector and pull injector out of fuel rail.
The clip will stay on the injector.
(4) Check injector O-ring for damage. If O-ring is
damaged, it must be replaced. If injector is reused, a
protective cap must be installed on the injector tip to
prevent damage. Replace the injector clip if it is dam-
aged.
(5) Repeat for remaining injectors.
REMOVAL - 3.3/3.8L
(1) Disconnect the negative battery cable.
(2) Remove the Intake Manifold, (Refer to 9 -
ENGINE/MANIFOLDS/INTAKE MANIFOLD -
REMOVAL)
Fig. 10 Fuel Injector Location - Typical
1 - FUEL RAIL
2 - INTAKE MANIFOLD
3 - FUEL INJECTORS
Fig. 11 FUEL INJECTOR - TYPICAL
1 - FUEL INJECTOR
2 - NOZZLE
3 - TOP (FUEL ENTRY)
Fig. 12 FUEL RAIL AND INJECTORS 2.4L
1 - Fuel Injectors
2 - Fuel Rail
Fig. 13 FUEL INJECTOR AND RAIL TYPICAL
1 - FUEL RAIL ASSEMBLY
2 - FUEL INJECTOR
3 - FUEL RAIL RECEIVER
RSFUEL INJECTION14-27
FUEL INJECTOR (Continued)

(3) Disconnect injector wiring connector from injec-
tor.
(4) Position fuel rail assembly so that the fuel
injectors are easily accessible (Fig. 13).
(5) Rotate injector and pull injector out of fuel rail.
The clip will stay on the injector.
(6) Check injector O-ring for damage. If O-ring is
damaged, it must be replaced. If injector is reused, a
protective cap must be installed on the injector tip to
prevent damage. Replace the injector clip if it is dam-
aged.
(7) Repeat for remaining injectors.
INSTALLATION
INSTALLATION - 2.4L
The fuel rail must be removed first. Refer to Fuel
Injector Rail Removal in this section.
(1) Before installing an injector the rubber O-ring
must be lubricated with a drop of clean engine oil to
aid in installation.
(2) Install injector clip by sliding open end into the
top slot of the injector. The edge of the receiver cup
will slide into the side slots of clip.
(3) Install injector top end into fuel rail receiver
cap. Be careful not to damage O-ring during installa-
tion (Fig. 14).
(4) Repeat steps for remaining injectors.
(5) Connect fuel injector wiring.
INSTALLATION - 3.3/3.8L
(1) Before installing an injector the rubber O-ring
must be lubricated with a drop of clean engine oil to
aid in installation.(2) Install injector clip by sliding open end into the
top slot of the injector. The edge of the receiver cup
will slide into the side slots of clip (Fig. 13).
(3) Install injector top end into fuel rail receiver
cap. Be careful not to damage O-ring during installa-
tion (Fig. 13).
(4) Repeat steps for remaining injectors.
(5) Install fuel rail, refer to Fuel Rail in the Fuel
Delivery section.
(6) Connect fuel injector wiring.
(7) Install the Intake Manifold, (Refer to 9 -
ENGINE/MANIFOLDS/INTAKE MANIFOLD -
INSTALLATION)
(8) Connect the negative battery cable.
FUEL PUMP RELAY
DESCRIPTION
The fuel pump relay is located in the PDC. The
inside top of the PDC cover has a label showing relay
and fuse location.
OPERATION
The fuel pump relay supplies battery voltage to the
fuel pump. A buss bar in the Power Distribution Cen-
ter (PDC) supplies voltage to the solenoid side and
contact side of the relay. The fuel pump relay power
circuit contains a fuse between the buss bar in the
PDC and the relay. The fuse is located in the PDC.
Refer to the Wiring Diagrams for circuit information.
The PCM controls the fuel pump relay by switch-
ing the ground path for the solenoid side of the relay
on and off. The PCM turns the ground path off when
the ignition switch is in the Off position. When the
ignition switch is in the On position, the PCM ener-
gizes the fuel pump. If the crankshaft position sensor
does not detect engine rotation, the PCM de-ener-
gizes the relay after approximately one second.
IDLE AIR CONTROL MOTOR
DESCRIPTION
The idle air control valve is mounted on the throt-
tle body. The PCM operates the idle air control valve
(Fig. 15) or (Fig. 16).
OPERATION
The PCM adjusts engine idle speed through the
idle air control valve to compensate for engine load,
coolant temperature or barometric pressure changes.
The throttle body has an air bypass passage that
provides air for the engine during closed throttle idle.
The idle air control valve regulates air flow through
the bypass passage.
Fig. 14 SERVICING FUEL INJECTOR TYPICAL
1 - FUEL INJECTOR
2 - LOCKING SLOT
3 - FUEL RAIL RECEIVER CUP
14 - 28 FUEL INJECTIONRS
FUEL INJECTOR (Continued)

O2 SENSOR
DESCRIPTION
The upstream oxygen sensor threads into the out-
let flange of the exhaust manifold (Fig. 22) or (Fig.
23).
The downstream heated oxygen sensor threads into
the outlet pipe at the rear of the catalytic convertor
(Fig. 24).
OPERATION
A seperate upstream and downstream grounds are
used on the NGC vehicles (4 Cyl.).
As vehicles accumulate mileage, the catalytic con-
vertor deteriorates. The deterioration results in aless efficient catalyst. To monitor catalytic convertor
deterioration, the fuel injection system uses two
heated oxygen sensors. One sensor upstream of the
catalytic convertor, one downstream of the convertor.
The PCM compares the reading from the sensors to
calculate the catalytic convertor oxygen storage
capacity and converter efficiency. Also, the PCM uses
the upstream heated oxygen sensor input when
adjusting injector pulse width.
When the catalytic converter efficiency drops below
emission standards, the PCM stores a diagnostic
trouble code and illuminates the malfunction indica-
tor lamp (MIL).
The O2 sensors produce a constant 2.5 volts on
NGC vehicles, depending upon the oxygen content of
the exhaust gas. When a large amount of oxygen is
present (caused by a lean air/fuel mixture, can be
caused by misfire and exhaust leaks), the sensors
produces a low voltage. When there is a lesser
amount of oxygen present (caused by a rich air/fuel
mixture, can be caused by internal engine problems)
it produces a higher voltage. By monitoring the oxy-
gen content and converting it to electrical voltage,
the sensors act as a rich-lean switch.
The oxygen sensors are equipped with a heating
element that keeps the sensors at proper operating
temperature during all operating modes. Maintaining
correct sensor temperature at all times allows the
system to enter into closed loop operation sooner.
Also, it allows the system to remain in closed loop
operation during periods of extended idle.
In Closed Loop operation the PCM monitors the O2
sensors input (along with other inputs) and adjusts
the injector pulse width accordingly. During Open
Loop operation the PCM ignores the O2 sensor input.
Fig. 22 O2 SENSOR UPSTREAM 1/1 - 2.4L
Fig. 23 O2 SENSOR UPSTREAM 1/1 - 3.3/3.8L
Fig. 24 O2 SENSOR DOWNSTREAM 1/2 - 2.4/3.3/
3.8L
14 - 32 FUEL INJECTIONRS