2000 DODGE NEON relay

FUEL TUBES/LINES/HOSES AND CLAMPS
OPERATION
Also refer to Quick-Connect Fittings.
WARNING: THE FUEL SYSTEM IS UNDER A CON-
STANT PRESSURE (EVEN WITH THE ENGINE OFF).
BEFORE SERVICING ANY FUEL SYSTEM HOSES,
FITTINGS OR LINES, THE FUEL SYSTEM PRES-
SURE MUST BE RELEASED. REFER TO THE FUEL
SYSTEM PRESSURE RELEASE PROCEDURE IN
THIS GROUP.
Inspect all hose connections such as clamps, cou-
plings and fittings to make sure they are secure and
leaks are not present. The component should be
replaced immediately if there is any evidence of deg-
radation that could result in failure.
Never attempt to repair a plastic fuel line/tube.
Replace as necessary.
Avoid contact of any fuel tubes/hoses with other
vehicle components that could cause abrasions or
scuffing. Be sure that the plastic fuel lines/tubes areproperly routed to prevent pinching and to avoid heat
sources.
The lines/tubes/hoses used on fuel injected vehicles
are of a special construction. This is due to the
higher fuel pressures and the possibility of contami-
nated fuel in this system. If it is necessary to replace
these lines/tubes/hoses, only those marked EFM/EFI
may be used.
If equipped:The hose clamps used to secure rub-
ber hoses on fuel injected vehicles are of a special
rolled edge construction. This construction is used to
prevent the edge of the clamp from cutting into the
hose. Only these rolled edge type clamps may be
used in this system. All other types of clamps may
cut into the hoses and cause high-pressure fuel leaks.
Use new original equipment type hose clamps.
Tighten hose clamps to 3 N´m (25 in. lbs.) torque.
SERVICE PROCEDURES
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.
CAUTION: Steps 1, 2, 3 and 4 must be performed to
relieve high pressure fuel from within fuel rail. Do
not attempt to use following steps to relieve this
pressure as excessive fuel will be forced into a cyl-
inder chamber.
(5) Place a rag or towel below fuel line quick-con-
nect fitting at fuel rail.
(6) Return fuel pump relay to PDC.
(7) 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.
INJECTOR CONNECTOR
REMOVAL
(1) Disconnect electrical connectors at the fuel
injectors. To remove connector refer to (Fig. 8). Pull
the red colored slider away from injector (1). While
pulling the slider, depress tab (2) and remove connec-
tor (3) from injector. The factory fuel injection wiring
harness is numerically tagged (INJ 1, INJ 2, etc.) for
injector position identification. If harness is not
tagged, make note of wiring location before removal.
Fig. 6 Plastic Quick-Connect Fittings
1 ± CASING
2 ± WINDOW
3 ± RETAINER TAB
4 ± NIPPLE
5 ± O RINGS
6 ± WINDOW
7 ± RETAINER ªEARº
14 - 8 FUEL SYSTEMPL
DESCRIPTION AND OPERATION (Continued)

(3) Squeeze retainer tabs together and pull fuel
tube/quick-connect fitting assembly off of fuel tube
nipple. The retainer will remain on fuel tube.
INSTALLATION
CAUTION: Never install a quick-connect fitting
without the retainer being either on the fuel tube or
already in the quick-connect fitting. In either case,
ensure the retainer locks securely into the quick-
connect fitting by firmly pulling on fuel tube and fit-
ting to ensure it is secured.
(1) Using a clean lint free cloth, clean the fuel tube
nipple and retainer.
(2) Prior to connecting the fitting to the fuel tube,
coat the fuel tube nipple with clean 30 weight engine
oil.
(3) Push the quick-connect fitting over the fuel
tube until theretainer seats and a click is heard.
(4) The plastic quick-connect fitting has windows
in the sides of the casing. When the fitting com-
pletely attaches to the fuel tube, the retainer locking
ears and the fuel tube shoulder are visible in the
windows. If they are not visible, the retainer was not
properly installed (Fig. 9).Do not rely upon the
audible click to confirm a secure connection.
(5) Connect negative cable to battery or auxiliary
jumper terminal.
CAUTION: When using the ASD Fuel System Test,
the Auto Shutdown (ASD) Relay remains energized
for either 7 minutes, until the test is stopped, or
until the ignition switch is turned to the Off posi-
tion.(6) Use the DRB scan tool ASD Fuel System Test
to pressurize the fuel system. Check for leaks.
TWO-TAB TYPE FITTING
This type of fitting is equipped with tabs located on
both sides of the fitting (Fig. 10). These tabs are sup-
plied for disconnecting the quick-connect fitting from
component being serviced.
CAUTION: The interior components (O-rings, spac-
ers) of this type of quick-connect fitting are not ser-
viced separately, but new plastic retainers are
available. Do not attempt to repair damaged fittings
or fuel lines/tubes. If repair is necessary, replace
the complete fuel tube assembly.
WARNING:
THE FUEL SYSTEM IS UNDER A CON-
STANT PRESSURE (EVEN WITH THE ENGINE OFF).
BEFORE SERVICING ANY FUEL SYSTEM HOSES, FIT-
TINGS OR LINES, THE FUEL SYSTEM PRESSURE
MUST BE RELEASED. REFER TO THE FUEL PRES-
SURE RELEASE PROCEDURE IN THIS GROUP.
DISCONNECTION/CONNECTION
(1) Perform fuel pressure release procedure. Refer
to Fuel Pressure Release Procedure in this group.
(2) Disconnect negative battery cable from battery
or auxiliary jumper terminal.
(3) Clean fitting of any foreign material before dis-
assembly.
(4) To disconnect quick-connect fitting, squeeze
plastic retainer tabs (Fig. 10) against sides of quick-
connect fitting with your fingers. Tool use is not
required for removal and may damage plastic
retainer. Pull fitting from fuel system component
Fig. 9 Plastic Quick-Connect Fitting/Fuel Tube
Connection
1 ± WINDOW
2 ± TAB (2)
3 ± EAR
4 ± SHOULDER (ON TUBE)
Fig. 10 Typical Two-Tab Type Quick-Connect Fitting
1 ± TAB(S)
2 ± QUICK-CONNECT FITTING
14 - 10 FUEL SYSTEMPL
SERVICE PROCEDURES (Continued)

REMOVAL AND INSTALLATION
AUTOMATIC SHUTDOWN RELAY
The relay is located in the Power Distribution Cen-
ter (PDC) (Fig. 12). The PDC is located next to the
battery in the engine compartment. For the location
of the relay within the PDC, refer to the PDC cover
for location. Check electrical terminals for corrosion
and repair as necessary.
FUEL PUMP RELAY
The fuel pump relay is located in the PDC. The
inside top of the PDC cover has a label showing relay
and fuse location.
FUEL PUMP MODULE
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) Drain the fuel. Refer to Draining Fuel Tank in
the Fuel Tank section of this group.
WARNING: THE FUEL RESERVOIR OF THE FUEL
PUMP MODULE DOES NOT EMPTY OUT WHEN THE
TANK IS DRAINED. THE FUEL IN THE RESERVOIR
WILL SPILL OUT WHEN THE MODULE IS
REMOVED.
(2) Remove fuel tank, refer to the Fuel Tank
removal/installation section.
(3) Lower tank.(4) Use Special Tool 6856 to remove fuel pump
module locknut (Fig. 15).
(5) Remove fuel pump and O-ring seal from tank.
Discard old seal.
INSTALLATION
(1) Wipe seal area of tank clean and place a new
seal in position in the tank opening.
(2) Position fuel pump in the tank. Make sure the
alignment tab on the underside of the fuel pump
module flange sits in the notch on the fuel tank (Fig.
14).
(3) Position the locknut over the fuel pump mod-
ule.
Fig. 12 Power Distribution Center (PDC)
Fig. 13 Fuel Pump Module Removal
1 ± FUEL FILTER/PRESSURE REGULATOR
2 ± FUEL LINE
3 ± LOCKNUT
Fig. 14 Alignment Tab
14 - 12 FUEL SYSTEMPL

(7) Disconnect fuel pump module electrical connec-
tor and ground wire (Fig. 31).
(8) Disconnect the fuel tube from Fuel Filter/Reg-
ulator. Refer to Quick Connect Fittings in the Fuel
Delivery section of this group.
(9) Disconnect fuel filler tube and filler vent tube
from filler hose at fuel tank.
(10) Support tank with transmission jack. Loosen
tank mounting straps and lower tank slightly.
(11) Remove tank mounting straps and lower tank.
INSTALLATION
(1) Position fuel tank on transmission jack.
(2) Raise tank into position.
(3) Tighten fuel tank strap nuts to 22.5 N´m (200
in. lbs.) torque. Remove transmission jack. Ensure
straps are not twisted or bent.(4) Connect fuel filler tube tank inlet nipple.
Tighten clamp.
(5) Connect EVAP vent hose.
(6) Attach fuel tubes to pump module and chassis
fuel tube. Refer to Quick Connect Fittings in the Fuel
Delivery section of this Group.
(7) Attach electrical connector and ground wire to
fuel pump module.
(8) Install vapor lines to EVAP canister.
(9) Install EVAP canister.
(10) Lower vehicle.
(11) Fill fuel tank, install filler cap, and connect
battery cable.
CAUTION: When using the ASD Fuel System Test,
the Auto Shutdown (ASD) Relay remains energized
for either 7 minutes, until the test is stopped, or
until the ignition switch is turned to the Off posi-
tion.
(12) Use the DRB scan tool ASD Fuel System Test
to pressurize the fuel system. Check for leaks.
FUEL FILLER NECK
REMOVAL
(1) Loosen fuel filler tube cap.
(2) Remove fuel filler neck screws (Fig. 32).
(3) Raise and support vehicle.
(4) Remove splash shield from wheel well.
(5) Disconnect fuel fill vapor tube.
(6) Disconnect fuel filler tube from fuel tank.
(7) Remove groundstrap from body.
(8) Remove filler neck (Fig. 33).
Fig. 29 EVAP Canister
Fig. 30 Fuel Tank
Fig. 31 Pump Module Electrical Connector
1 ± ELECTRICAL CONNECTOR
2 ± FUEL LINE
PLFUEL SYSTEM 14 - 17
REMOVAL AND INSTALLATION (Continued)

FUEL INJECTION SYSTEM
TABLE OF CONTENTS
page page
DESCRIPTION AND OPERATION
INJECTION SYSTEM......................22
MODES OF OPERATION...................22
SYSTEM DIAGNOSIS......................24
POWER DISTRIBUTION CENTER............24
POWERTRAIN CONTROL MODULE...........24
PCM GROUND...........................26
5 VOLT SUPPLYÐPCM OUTPUT.............26
8-VOLT SUPPLYÐPCM OUTPUT.............26
FUEL CORRECTION or ADAPTIVE MEMORIES . . 26
PROGRAMMABLE COMMUNICATIONS
INTERFACE (PCI) BUS...................27
AIR CONDITIONING PRESSURE
TRANSDUCERÐPCM INPUT..............27
AUTOMATIC SHUTDOWN (ASD) SENSEÐ
PCM INPUT...........................27
BATTERY VOLTAGEÐPCM INPUT............28
BRAKE SWITCHÐPCM INPUT...............28
CAMSHAFT POSITION SENSORÐPCM INPUT . . 28
CLUTCH INTERLOCK/UPSTOP SWITCH.......29
CRANKSHAFT POSITION SENSORÐPCM
INPUT................................30
ENGINE COOLANT TEMPERATURE
SENSORÐPCM INPUT...................30
FUEL LEVEL SENSORÐPCM INPUT..........31
HEATED OXYGEN SENSOR (O2 SENSOR)Ð
PCM INPUT...........................32
IGNITION CIRCUIT SENSEÐPCM INPUT......34
INLET AIR TEMPERATURE SENSORÐPCM
INPUT................................34
KNOCK SENSORÐPCM INPUT..............34
MANIFOLD ABSOLUTE PRESSURE (MAP)
SENSORÐPCM INPUT...................35
POWER STEERING PRESSURE SWITCHÐ
PCM INPUT...........................35
SENSOR RETURNÐPCM INPUT.............35
SPEED CONTROLÐPCM INPUT.............36
SCI RECEIVEÐPCM INPUT.................36
PARK/NEUTRAL POSITION SWITCHÐPCM
INPUT................................36
THROTTLE POSITION SENSORÐPCM INPUT . . 36VEHICLE SPEED SIGNAL (VSS)ÐPCM INPUT . . 37
AIR CONDITIONING CLUTCH RELAYÐPCM
OUTPUT..............................38
AUTOMATIC SHUTDOWN RELAYÐPCM
OUTPUT..............................38
CHARGING SYSTEM INDICATOR LAMPÐPCM
OUTPUT..............................38
FUEL PUMP RELAYÐPCM OUTPUT..........38
PROPORTIONAL PURGE SOLENOIDÐPCM
OUTPUT..............................39
GENERATOR FIELDÐPCM OUTPUT..........39
IDLE AIR CONTROL MOTORÐPCM OUTPUT . . . 39
DATA LINK CONNECTOR...................40
FUEL INJECTORSÐPCM OUTPUT...........40
IGNITION COILÐPCM OUTPUT..............40
MALFUNCTION INDICATOR (CHECK ENGINE)
LAMPÐPCM OUTPUT...................41
SPEED CONTROLÐPCM INPUT.............41
SCI RECEIVEÐPCM OUTPUT...............41
TACHOMETERÐPCM OUTPUT..............42
TORQUE CONVERTOR CLUTCH SOLENOIDÐ
PCM OUTPUT..........................42
REMOVAL AND INSTALLATION
THROTTLE BODY........................42
THROTTLE POSITION SENSOR.............43
IDLE AIR CONTROL MOTOR................43
MAP SENSOR...........................44
POWERTRAIN CONTROL MODULE (PCM).....44
UPSTREAM HEATED OXYGEN SENSOR......45
DOWNSTREAM HEATED OXYGEN SENSOR
1/2 ..................................46
AIR CLEANER BOX.......................46
AIR CLEANER ELEMENT...................47
ENGINE COOLANT TEMPERATURE SENSOR . . . 47
VEHICLE SPEED SENSOR.................47
KNOCK SENSOR.........................48
SPECIFICATIONS
VECI LABEL.............................49
TORQUE...............................49
SPECIAL TOOLS
FUEL..................................49
PLFUEL SYSTEM 14 - 21

DESCRIPTION AND OPERATION
INJECTION SYSTEM
All engines used in this section have a sequential
Multi-Port Electronic Fuel Injection system. The MPI
system is computer regulated and provides precise
air/fuel ratios for all driving conditions. The Power-
train Control Module (PCM) operates the fuel injec-
tion system.
The PCM regulates:
²Ignition timing
²Air/fuel ratio
²Emission control devices
²Cooling fan
²Charging system
²Idle speed
²Vehicle speed control
Various sensors provide the inputs necessary for
the PCM to correctly operate these systems. In addi-
tion to the sensors, various switches also provide
inputs to the PCM.
All inputs to the PCM are converted into signals.
The PCM can adapt its programming to meet chang-
ing operating conditions.
Fuel is injected into the intake port above the
intake valve in precise metered amounts through
electrically operated injectors. The PCM fires the
injectors in a specific sequence. Under most operat-
ing conditions, the PCM maintains an air fuel ratio
of 14.7 parts air to 1 part fuel by constantly adjust-
ing injector pulse width. Injector pulse width is the
length of time the injector is open.
The PCM adjusts injector pulse width by opening
and closing the ground path to the injector. Engine
RPM (speed) and manifold absolute pressure (air
density) are the primary inputs that determine injec-
tor pulse width.
MODES OF OPERATION
OPERATION
As input signals to the PCM change, the PCM
adjusts its response to output devices. For example,
the PCM must calculate a different injector pulse
width and ignition timing for idle than it does for
Wide Open Throttle (WOT). There are several differ-
ent modes of operation that determine how the PCM
responds to the various input signals.
There are two different areas of operation, OPEN
LOOP and CLOSED LOOP.
During OPEN LOOP modes the PCM receives
input signals and responds according to preset PCM
programming. Inputs from the upstream and down-
stream heated oxygen sensors are not monitored dur-
ing OPEN LOOP modes, except for heated oxygensensor diagnostics (they are checked for shorted con-
ditions at all times).
During CLOSED LOOP modes the PCM monitors
the inputs from the upstream and downstream
heated oxygen sensors. The upstream heated oxygen
sensor input tells the PCM if the calculated injector
pulse width resulted in the ideal air-fuel ratio of 14.7
to one. By monitoring the exhaust oxygen content
through the upstream heated oxygen sensor, the
PCM can fine tune injector pulse width. Fine tuning
injector pulse width allows the PCM to achieve opti-
mum fuel economy combined with low emissions.
For the PCM to enter CLOSED LOOP operation,
the following must occur:
(1) Engine coolant temperature must be over 35ÉF.
²If the coolant is over 35É the PCM will wait 44
seconds.
²If the coolant is over 50ÉF the PCM will wait 38
seconds.
²If the coolant is over 167ÉF the PCM will wait
11 seconds.
(2) For other temperatures the PCM will interpo-
late the correct waiting time.
(3) O2 sensor must read either greater than 0.745
volts or less than 0.1 volt.
(4) The multi-port fuel injection systems has the
following modes of operation:
²Ignition switch ON (Zero RPM)
²Engine start-up
²Engine warm-up
²Cruise
²Idle
²Acceleration
²Deceleration
²Wide Open Throttle
²Ignition switch OFF
(5) The engine start-up (crank), engine warm-up,
deceleration with fuel shutoff and wide open throttle
modes are OPEN LOOP modes. Under most operat-
ing conditions, the acceleration, deceleration (with
A/C on), idle and cruise modes,with the engine at
operating temperatureare CLOSED LOOP modes.
IGNITION SWITCH ON (ZERO RPM) MODE
When the ignition switch activates the fuel injec-
tion system, the following actions occur:
²The PCM monitors the engine coolant tempera-
ture sensor and throttle position sensor input. The
PCM determines basic fuel injector pulse width from
this input.
²The PCM determines atmospheric air pressure
from the MAP sensor input to modify injector pulse
width.
When the key is in the ON position and the engine
is not running (zero rpm), the Auto Shutdown (ASD)
and fuel pump relays de-energize after approximately
14 - 22 FUEL SYSTEMPL

1 second. Therefore, battery voltage is not supplied to
the fuel pump, ignition coil, fuel injectors and heated
oxygen sensors.
ENGINE START-UP MODE
This is an OPEN LOOP mode. If the vehicle is in
park or neutral (automatic transaxles) or the clutch
pedal is depressed (manual transaxles) the ignition
switch energizes the starter relay. The following
actions occur when the starter motor is engaged.
²If the PCM receives the camshaft position sensor
and crankshaft position sensor signals, it energizes
the Auto Shutdown (ASD) relay and fuel pump relay.
If the PCM does not receive both signals within
approximately one second, it will not energize the
ASD relay and fuel pump relay. The ASD and fuel
pump relays supply battery voltage to the fuel pump,
fuel injectors, ignition coil and heated oxygen sen-
sors.
²The PCM energizes the injectors (on the 69É
degree falling edge) for a calculated pulse width until
it determines crankshaft position from the camshaft
position sensor and crankshaft position sensor sig-
nals. The PCM determines crankshaft position within
1 engine revolution.
²After determining crankshaft position, the PCM
begins energizing the injectors in sequence. It adjusts
injector pulse width and controls injector synchroni-
zation by turning the individual ground paths to the
injectors On and Off.
²When the engine idles within664 RPM of its
target RPM, the PCM compares current MAP sensor
value with the atmospheric pressure value received
during the Ignition Switch On (zero RPM) mode. If
the PCM does not detect a minimum difference
between the two values, it sets a MAP diagnostic
trouble code into memory.
Once the ASD and fuel pump relays have been
energized, the PCM determines injector pulse width
based on the following:
²Battery voltage
²Engine coolant temperature
²Engine RPM
²Intake air temperature (IAT)
²Throttle position
²The number of engine revolutions since cranking
was initiated.
During Start-up the PCM maintains ignition tim-
ing at 9É BTDC.
ENGINE WARM-UP MODE
This is an OPEN LOOP mode. The following inputs
are received by the PCM:
²Engine coolant temperature
²Manifold Absolute Pressure (MAP)
²Intake air temperature (IAT)²Crankshaft position (engine speed)
²Camshaft position
²Knock sensor
²Throttle position
²A/C switch
²Battery voltage
²Power steering pressure switch
²Vehicle speed
²Speed control
²O2 sensors
²All diagnostics
The PCM adjusts injector pulse width and controls
injector synchronization by turning the individual
ground paths to the injectors On and Off.
The PCM adjusts ignition timing and engine idle
speed. Engine idle speed is adjusted through the idle
air control motor.
CRUISE OR IDLE MODE
When the engine is at operating temperature this
is a CLOSED LOOP mode. During cruising or idle
the following inputs are received by the PCM:
²Intake air temperature
²Engine coolant temperature
²Manifold absolute pressure
²Crankshaft position (engine speed)
²Camshaft position
²Knock sensor
²Throttle position
²Exhaust gas oxygen content
²A/C control positions
²Power steering pressure switch
²Battery voltage
²Vehicle speed
The PCM adjusts injector pulse width and controls
injector synchronization by turning the individual
ground paths to the injectors On and Off.
The PCM adjusts engine idle speed and ignition
timing. The PCM adjusts the air/fuel ratio according
to the oxygen content in the exhaust gas (measured
by the upstream and downstream heated oxygen sen-
sor).
The PCM monitors for engine misfire. During
active misfire and depending on the severity, the
PCM either continuously illuminates or flashes the
malfunction indicator lamp (Check Engine light on
instrument panel). Also, the PCM stores an engine
misfire DTC in memory.
The PCM performs several diagnostic routines.
They include:
²Oxygen sensor monitor
²Downstream heated oxygen sensor diagnostics
during open loop operation (except for shorted)
²Fuel system monitor
²EGR monitor
²Purge system monitor
PLFUEL SYSTEM 14 - 23
DESCRIPTION AND OPERATION (Continued)

²All inputs monitored for proper voltage range.
²All monitored components (refer to the Emission
section for On-Board Diagnostics).
The PCM compares the upstream and downstream
heated oxygen sensor inputs to measure catalytic
convertor efficiency. If the catalyst efficiency drops
below the minimum acceptable percentage, the PCM
stores a diagnostic trouble code in memory.
During certain idle conditions, the PCM may enter
a variable idle speed strategy. During variable idle
speed strategy the PCM adjusts engine speed based
on the following inputs.
²A/C sense
²Battery voltage
²Battery temperature
²Engine coolant temperature
²Engine run time
²Power steering pressure switch
²Vehicle mileage
ACCELERATION MODE
This is a CLOSED LOOP mode. The PCM recog-
nizes an abrupt increase in Throttle Position sensor
output voltage or MAP sensor output voltage as a
demand for increased engine output and vehicle
acceleration. The PCM increases injector pulse width
in response to increased fuel demand.
DECELERATION MODE
This is a CLOSED LOOP mode. During decelera-
tion the following inputs are received by the PCM:
²A/C pressure transducer
²A/C sense
²Battery voltage
²Intake air temperature
²Engine coolant temperature
²Crankshaft position (engine speed)
²Exhaust gas oxygen content (upstream heated
oxygen sensor)
²Knock sensor
²Manifold absolute pressure
²Power steering pressure switch
²Throttle position
²IAC motor control changes in response to MAP
sensor feedback.
The PCM may receive a closed throttle input from
the Throttle Position Sensor (TPS) when it senses an
abrupt decrease in manifold pressure. This indicates
a hard deceleration. In response, the PCM may
momentarily turn off the injectors. This helps
improve fuel economy, emissions and engine braking.
If decel fuel shutoff is detected, downstream oxy-
gen sensor diagnostics is performed.WIDE-OPEN-THROTTLE MODE
This is an OPEN LOOP mode. During wide-open-
throttle operation, the following inputs are received
by the PCM:
²Intake air temperature
²Engine coolant temperature
²Engine speed
²Knock sensor
²Manifold absolute pressure
²Throttle position
When the PCM senses a wide-open-throttle condi-
tion through the Throttle Position Sensor (TPS) it de-
energizes the A/C compressor clutch relay. This
disables the air conditioning system.
The PCM does not monitor the heated oxygen sen-
sor inputs during wide-open-throttle operation except
for downstream heated oxygen sensor and both
shorted diagnostics. The PCM adjusts injector pulse
width to supply a predetermined amount of addi-
tional fuel.
IGNITION SWITCH OFF MODE
When the operator turns the ignition switch to the
OFF position, the following occurs:
²All outputs are turned off, unless 02 Heater
Monitor test is being run. Refer to the Emission sec-
tion for On-Board Diagnostics.
²No inputs are monitored except for the heated
oxygen sensors. The PCM monitors the heating ele-
ments in the oxygen sensors and then shuts down.
SYSTEM DIAGNOSIS
OPERATION
The PCM can test many of its own input and out-
put circuits. If the PCM senses a fault in a major
system, the PCM stores a Diagnostic Trouble Code
(DTC) in memory.
For DTC information see On-Board Diagnostics.
POWER DISTRIBUTION CENTER
The Power Distribution Center (PDC) is located
next to the battery (Fig. 1). The PDC contains the
starter relay, radiator fan relay, A/C compressor
clutch relay, auto shutdown relay, fuel pump relay
and several fuses.
POWERTRAIN CONTROL MODULE
The Powertrain Control Module (PCM) is a digital
computer containing a microprocessor (Fig. 2). The
PCM receives input signals from various switches
and sensors that are referred to as PCM Inputs.
Based on these inputs, the PCM adjusts various
engine and vehicle operations through devices that
are referred to as PCM Outputs.
PCM Inputs:
14 - 24 FUEL SYSTEMPL
DESCRIPTION AND OPERATION (Continued)