mileage DODGE NEON 2000 Service Repair Manual

MAINTENANCE SCHEDULES
TABLE OF CONTENTS
page page
DESCRIPTION AND OPERATION
MAINTENANCE SCHEDULES................3
SPECIFICATIONS
UNSCHEDULED INSPECTION................3SCHEDULE ± A...........................3
SCHEDULE ± B...........................4
DESCRIPTION AND OPERATION
MAINTENANCE SCHEDULES
There are two maintenance schedules that show
proper service for your vehicle.
First is Schedule ±A. It lists all the scheduled
maintenance to be performed under ªnormalº operat-
ing conditions.
Second is Schedule ±B. It is a schedule for vehi-
cles that are operated under the following conditions:
²Frequent short trip driving less than 5 miles (8
km)
²Frequent driving in dusty conditions
²Extensive idling
²More than 50% of the driving is at sustained
high speeds during hot weather, above 90É F (32É C)
SPECIFICATIONS
UNSCHEDULED INSPECTION
At Each Stop For Fuel
²Check engine oil level and add as required.
²Check windshield washer solvent and add as
required.
Once A Month
²Check tire pressure and look for unusual wear
or damage.
²Inspect the battery and clean and tighten termi-
nals as required.
²Check fluid levels of coolant reservoir, brake
master cylinder, power steering and transmission.
Add fluid as required.
²Check all lights and all other electrical items for
correct operation.
At Each Oil Change
²Inspect the exhaust system.
²Inspect brake hoses.
²Inspect the CV joints and front suspension com-
ponent boots and seals.²Rotate the tires at each oil change interval
shown on Schedule ± A (7,500 miles - 12 000 km) or
every other interval on Schedule ± B (6,000 miles -
10 000 km).
²Check the engine coolant level, hoses, and
clamps.
If mileage is less than 7,500 miles (12 000 km)
yearly, replace the engine oil filter at each oil change.
EMISSION CONTROL SYSTEM MAINTENANCE
The scheduled emission maintenance listed inbold
typeon the Maintenance Schedules, must be done at
the mileage specified to assure the continued proper
functioning of the emission control system. These,
and all other maintenance services included in this
manual, should be done to provide the best vehicle
performance and reliability. More frequent mainte-
nance may be needed for vehicles in severe operating
conditions such as dusty areas and very short trip
driving.
FLUID FILL POINTS AND LUBRICATION
LOCATIONS
The fluid fill/check locations and lubrication loca-
tions are located in each applicable group.
SCHEDULE ± A
7,500 Miles (12 000 km) or at 6 months
²Change the engine oil.
²Replace the engine oil filter.
15,000 Miles (24 000 km) or at 12 months
²Change the engine oil.
²Replace the engine oil filter.
²Adjust the drive belt tension.
22,500 Miles (36 000 km) or at 18 months
²Change the engine oil.
²Replace the engine oil filter.
²Inspect the front brake pads and rear brake lin-
ings.
PLLUBRICATION AND MAINTENANCE 0 - 3

30,000 Miles (48 000 km) or at 24 months
²Change the engine oil.
²Replace the engine oil filter.
²Lubricate the front suspension lower ball joint.
²Inspect the tie rod ends and boot seals.
²Adjust the drive belt tension.
²Replace the engine air cleaner element (fil-
ter).
²Replace the engine spark plugs
²Change the automatic transaxle fluid.
37,500 Miles (60 000 km) or at 30 months
²Change the engine oil.
²Replace the engine oil filter.
45,000 Miles (72 000 km) or at 36 months
²Change the engine oil.
²Replace the engine oil filter.
²Inspect the front brake pads and rear brake lin-
ings.
²Adjust the drive belt tension.
²Flush and replace the engine coolant at 36
months, regardless of mileage.
52,500 Miles (84 000 km) or at 42 months
²Change the engine oil.
²Replace the engine oil filter.
²Flush and replace the engine coolant if not done
at 36 months.
60,000 Miles (96 000 km) or at 48 months
²Change the engine oil.
²Replace the engine oil filter.
²Check the PCV valve and replace, if neces-
sary. Not required if previously changed.*
²Lubricate the front suspension lower ball joints.
²Replace the drive belts.
²Replace the engine air cleaner element (fil-
ter).
²Replace the ignition cables.
²Replace the spark plugs.
²Change the automatic transaxle fluid.
67,500 Miles (108 000 km) or at 54 months
²Change the engine oil.
²Replace the engine oil filter.
²Inspect the front brake pads and rear brake lin-
ings.
75,000 Miles (120 000 km) or at 60 months
²Change the engine oil.
²Replace the engine oil filter.
²Adjust the drive belt tension.
²Flush and replace engine coolant if has been
30,000 miles (48 000 km) or 24 months since last
change.
82,500 Miles (132 000 km) or at 66 months
²Change the engine oil.
²Replace the engine oil filter.
²Flush and replace engine coolant if it has been
30,000 miles (48 000 km) or 24 months since last
change.
90,000 Miles (144 000 km) or at 72 months
²Change the engine oil.
²Replace the engine oil filter.
²Check the PCV valve and replace, if neces-
sary. Not required if previously changed.*
²Lubricate the front suspension lower ball joints.
²Inspect the front brake pads and rear brake lin-
ings.
²Adjust the drive belt tension.
²Replace the engine air cleaner element (fil-
ter).
²Replace the spark plugs.
²Inspect the serpentine drive belt, replace if nec-
essary. This maintenance is not required if the belt
was previously replaced.
²Change the automatic transaxle fluid.
97,500 Miles (156 000 km) or at 78 months
²Change the engine oil.
²Replace the engine oil filter.
105,000 Miles (168 000 km) or at 84 months
²Change the engine oil.
²Replace the engine oil filter.
²Replace the engine timing belt.
²Adjust the drive belt tension.
*This maintenance is recommended by Daimler-
Chrysler Corporation to the owner but is not
required to maintain the emissions warranty.
NOTE: Inspection and service should also be per-
formed anytime a malfunction is observed or sus-
pected. Retain all receipts.
SCHEDULE ± B
3,000 Miles (5 000 km)
²Change the engine oil.
6,000 Miles (10 000 km)
²Change the engine oil.
²Replace the engine oil filter.
9,000 Miles (14 000 km)
²Change the engine oil.
²Inspect the front brake pads and rear brake lin-
ings.
0 - 4 LUBRICATION AND MAINTENANCEPL
SPECIFICATIONS (Continued)

CONDITION POSSIBLE CAUSE CORRECTION
TEMPERATURE GAUGE READS
HIGH OR ENGINE COOLANT
WARNING LAMP ILLUMINATES.
COOLANT MAY OR MAY NOT BE
LOST FROM SYSTEM. (CONT.)6. Poor seals at radiator cap. 6. (a) Check condition of cap and
cap seals. Refer to Radiator cap
Inspection. Replace cap if
necessary.
(b) Check condition of filler neck. If
neck is bent or damaged, replace
neck.
7. Coolant level low in radiator, but
not in coolant recovery/reserve
container. This indicates the
radiator is not drawing coolant from
the coolant recovery/reserve
container as the engine cools. As
the engine cools, a vacuum is
formed inside the cooling system. If
the radiator cap seals are defective,
or the cooling system has a leak, a
vacuum cannot be formed.7. (a) Check condition of radiator
cap and cap seals. Replace cap if
necessary.
(b) Check condition of filler neck.
Replace if damaged.
(c) Check condition of hose from
filler neck to coolant container. It
should be tight at both ends without
any kinks or tears. Replace hose as
necessary.
(d) Check coolant recovery/reserve
container and hose for blockage.
Repair as necessary.
8. Freeze point of coolant not
correct. Mixture ratio may be too
rich.8. Check coolant concentration.
Refer to Coolant Concentration
Testing in this section. Adjust
glycol-to-water ration as required.
9. Coolant not flowing through
system.9. Check for coolant flow at filler
neck with some coolant removed,
engine warm, and thermostat open.
Coolant should be observed flowing
through filler neck. If flow is not
observed, determine reason for lack
of flow and repair as necessary.
10. Radiator or A/C condenser fins
are dirty or clogged.10. Clean obstruction from fins.
11. Radiator core is plugged or
corroded.11. Replace or re-core radiator.
12. Fuel or ignition system
problems.12. Refer to Fuel and Ignition
System groups for diagnosis. Also
refer to the appropriate Powertrain
Diagnostic Procedure manual.
13. Dragging Brakes. 13. Inspect brake system and repair
as necessary. Refer to Group 5,
Brakes for diagnosis.
14 Bug screen or other aftermarket
accessory is being used causing
reduced air flow.14. Remove bug screen or
accessory.
15. Thermostat partially or
completely closed. This is more
prevalent on high mileage vehicles.15. Check thermostat operation and
replace as necessary. Refer to
thermostat in this section for
procedure.
7 - 8 COOLING SYSTEMPL
DIAGNOSIS AND TESTING (Continued)

ENGINE THERMOSTAT TESTING
The thermostat is operated by a wax filled con-
tainer (pellet) which is sealed. When heated coolant
reaches a predetermined temperature the wax pellet
expands enough to overcome the closing spring and
water pump pressure, which forces the valve to open.
Coolant leakage into the pellet will cause a thermo-
stat to fail open. Do not attempt to free up a thermo-
stat with a screwdriver.
The thermostat that opens too soon type failure
mode is included in the on-board diagnosis. Thecheck engine light will not be lit by an open too soon
condition. If it has failed open, a diagnostic trouble
code (DTC) will be set. Do not change a thermostat
for lack of heater performance or temperature gauge
position, unless a DTC is present. See Diagnosis for
other probable causes. Thermostat failing shut is the
normal long term mode of failure, and normally, only
on high mileage vehicles. The temperature gauge will
indicate this. Refer to Diagnosis in this section.
ACCESSORY DRIVE BELT DIAGNOSIS
CONDITION POSSIBLE CAUSE CORRECTION
BELT SLIPPAGE 1. Belt slipping because of
insufficient tension.1. Retension generator belt.
Replace the power steering belt's
automatic belt tensioner.
2. Belt excessively glazed or
hardened from heat and excessive
slippage.2. Replace belt.
3. Incorrect belt. 3. Replace belt.
4. Driven component bearing
failure.4. Replace faulty component.
5. Belt or pulley subjected to
substance (belt dressing, oil,
ethylene glycol) that has reduced
friction.5. Replace belt and clean pulleys.
BELT NOISE (OBJECTIONABLE
SQUEAL, SQUEAK, OR RUMBLE)1. Belt slippage. 1. Retension generator belt, replace
belt, or automatic belt tensioner.
2. Foreign material imbedded in
belt.2. Replace belt.
3. Non-uniform belt. 3. Replace belt.
4. Misaligned pulley(s). 4. Align accessories.
5. Non-uniform groove or eccentric
pulley.5. Replace pulley(s).
6. Bearing noise. 6. Locate and repair.
BELT ROLLED OVER IN GROOVE
OR BELT JUMPS OFF1. Broken cord in belt. 1. Replace belt.
2. Belt tension too loose, or too
tight.2. Retension generator belt.
Replace the power steering belt's
automatic belt tensioner.
3. Misaligned pulleys. 3. Align accessories.
4. Non-uniform grooves or eccentric
pulley.4. Replace pulley(s).
5. Foreign object(s) in grooves. 5. Remove foreign objects in
groove.
7 - 14 COOLING SYSTEMPL
DIAGNOSIS AND TESTING (Continued)

COOLING SYSTEMÐDRAINING
NOTE: Drain, flush, and fill the cooling system at
the mileage or time intervals specified in Group 0,
Lubrication and Maintenance. If the solution is dirty,
rusty, or contains a considerable amount of sedi-
ment; clean and flush with a reliable cooling system
cleaner. Care should be taken in disposing of the
used engine coolant from your vehicle. Check gov-
ernmental regulations for disposal of used engine
coolant.
Without removing radiator pressure cap and
with system not under pressure:
(1) Shut engine off and turn draincock counter-
clockwise to open (Fig. 18).
(2) The coolant reserve tank should empty first,
then remove the pressure cap. (if not, Refer to Test-
ing Cooling System for leaks).
COOLING SYSTEMÐREFILLING
First clean system to remove old glycol, see Cooling
System Cleaning.
Fill system with 50/50 glycol/water mix. Use anti-
freeze described in Coolant section.
Continue filling system until full, this provides bet-
ter heater performance.Be careful not to spill
coolant on drive belts or the generator.
Fill coolant reserve/recovery system to at least the
FULL HOT mark with 50/50 solution. It may be nec-
essary to add coolant to the reserve/recovery con-
tainer after three or four warm-up/cool down cycles
to maintain coolant level between the FULL HOT
and ADD marks; if any trapped air was removed
from the system.
REMOVAL AND INSTALLATION
WATER PUMP
REMOVAL
(1) Raise vehicle on a hoist. Remove right inner
splash shield.
(2) Remove accessory drive belts. Refer to proce-
dure in this section.
(3) Drain cooling system. Refer to Cooling System
Draining in this section.
(4) Remove power steering pump attaching bolts
and set pump and assembly aside. Power steering
lines do not need to be disconnected.
(5) Remove upper and lower torque isolator struts.
(6) Support engine from the bottom and remove
right engine mount attaching bolt.
(7) Remove right engine mount bracket.
(8) Remove timing belt and timing belt tensioner.
Refer to Group 9, Engine for procedures.
(9) Remove camshaft sprocket and rear timing belt
cover. Refer to Group 9, Engine for procedures.
(10) Remove water pump attaching screws to
engine and remove pump (Fig. 19).
INSTALLATION
(1) Apply MopartDielectric Grease to O-ring
before installation.
(2) Install new O-ring gasket in water pump body
O-ring groove (Fig. 20).
CAUTION: Make sure O-ring gasket is properly
seated in water pump groove before tightening
screws. An improperly located O-ring may cause
damage to the O-ring, resulting in a coolant leak.
(3) Assemble pump body to block and tighten
screws to 12 N´m (105 in. lbs.). Pressurize cooling
system to 15 psi with pressure tester and check
water pump shaft seal and O-ring for leaks.
Fig. 18 Cooling System Drain Cock Location
1 ± DRAIN COCKFig. 19 Water Pump
1 ± CYLINDER BLOCK
2 ± PUMP BODY
PLCOOLING SYSTEM 7 - 19
SERVICE PROCEDURES (Continued)

IGNITION SYSTEM
TABLE OF CONTENTS
page page
DESCRIPTION AND OPERATION
IGNITION SYSTEM........................1
SPARK PLUGS...........................1
SPARK PLUG CABLES.....................1
ELECTRONIC IGNITION COILS...............2
AUTOMATIC SHUTDOWN RELAY.............2
CRANKSHAFT POSITION SENSORÐPCM
INPUT................................3
CAMSHAFT POSITION SENSORÐPCM
INPUT................................4
KNOCK SENSOR..........................5
IGNITION SWITCH........................5
LOCK KEY CYLINDER......................5
IGNITION INTERLOCK.....................6
REMOVAL AND INSTALLATION
SPARK PLUG SERVICE....................6SPARK PLUG CABLE SERVICE..............6
IGNITION COIL...........................6
AUTOMATIC SHUTDOWN RELAY.............6
CAMSHAFT POSITION SENSOR..............6
CRANKSHAFT POSITION SENSOR............8
KNOCK SENSOR..........................8
IGNITION SWITCH........................8
LOCK KEY CYLINDER......................9
IGNITION INTERLOCK....................10
SPECIFICATIONS
VECI LABEL............................10
FIRING ORDERÐ2.0L....................10
TORQUE SPECIFICATION..................11
SPARK PLUG CABLE RESISTANCEÐSOHC....11
SPARK PLUG...........................11
IGNITION COIL..........................11
DESCRIPTION AND OPERATION
IGNITION SYSTEM
DESCRIPTION
The system's three main components are the coil
pack, crankshaft position sensor, and camshaft posi-
tion sensor.
OPERATION
Basic ignition timing is not adjustable.The
Powertrain Control Module (PCM) determines spark
advance. The 2.0L engines use a fixed ignition timing
system. The distributorless electronic ignition system
is referred to as the Direct Ignition System (DIS).
SPARK PLUGS
The 2.0L engines uses resistor spark plugs. For
spark plug identification and specifications, Refer to
the Specifications section at the end of this group.
Remove the spark plugs and examine them for
burned electrodes and fouled, cracked or broken por-
celain insulators. Keep plugs arranged in the order
in which they were removed from the engine. An iso-
lated plug displaying an abnormal condition indicates
that a problem exists in the corresponding cylinder.
Spark plugs that have low mileage may be cleaned
and reused if not otherwise defective. Refer to the
Spark Plug Condition section of this group. Aftercleaning, file the center electrode flat with a small
point file or jewelers file. Adjust the gap between the
electrodes (Fig. 1) to the dimensions specified in the
chart at the end of this section by bending the
ground electrode (just above the attachment weld)
with the appropriate tool.
Never apply any force between the electrode or
damage to the center electrode assembly will result.
Always tighten spark plugs to the specified torque.
Over tightening can cause distortion and damage.
Tighten spark plugs to 28 N´m (20 ft. lbs.) torque.
SPARK PLUG CABLES
Spark plug cables are sometimes referred to as sec-
ondary ignition wires. The wires transfer electrical
current from the coil pack to individual spark plugs
at each cylinder. The resistor type, nonmetallic spark
plug cables provide suppression of radio frequency
emissions from the ignition system.
Check the spark plug cable connections for good
contact at the coil and spark plugs. Terminals should
be fully seated. The nipples and spark plug covers
should be in good condition. Nipples should fit tightly
on the coil. Spark plug boot should completely cover
the spark plug hole in the cylinder head cover. Install
the boot until the terminal snaps over the spark
plug. A snap must be felt to ensure the spark plug
cable terminal engaged the spark plug.
PLIGNITION SYSTEM 8D - 1

DESCRIPTION AND OPERATION
HEADLAMP SWITCH
The headlamp switch is part of the Multi-Function
Switch. Refer to Group 8J, Turn Signal and Flasher
for the Multi-Function Switch Test, Removal and
Installation procedures.
INSTRUMENT CLUSTER
There are two conventional instrument cluster
assemblies available. The clusters electronically drive
the speedometer, odometer, gauges, and tachometer
(if equipped). Refer to (Fig. 2) and (Fig. 3).
The instrument cluster controls the courtesy
lamps, it receives and sends messages to other mod-
ules via the PCI bus circuit, it controls all the instru-
ment illumination and the chime is also an integral
part of the cluster. The front turn signals are wired
through the cluster and then go to the front lamps.
The reason being that the DRL module is built into
the cluster (if equipped).
All gauges in the electronic clusters are the analog
type gauges. When the ignition switch is moved to
the OFF position, the cluster drives each gauge to its
lowest position. The individual gauges are not servi-
cable and require complete replacement of the cluster
if one or more gauges are inoperable.
One button is used to switch the display from trip
to total mileage. Holding the button when the display
is in the trip mode will reset the trip mileage. This
button is also used to put the cluster in self-diagnos-
tic mode. Refer to Service Procedures, Cluster Self-
Diagnostics in this section. Most of the indicators will
come on briefly for a bulb heck when the ignition is
turned from OFF to ON. All of the LED's are replace-
able.
In the event that the instrument cluster looses
communication with all other modules on the PCI
bus, the cluster will display ªnobusº in the VF dis-
play. The VF display also displays ªDoorº, ªCruiseº,
ªTracº, and odometer trip or total.
If the cluster does not detect voltage on the cour-
tesy lamp circuit, the message ªFUSEº will alternate
with the odometer/trip odometer for 30 seconds after
the ignition is turned on and for 15 seconds after the
vehicle is first moved. The lack of voltage can be due
to the M1 Fused B(+) (IOD) fuse being open, a bad or
missing courtesy lamp bulb, or a circuit problem.
WARNING AND INDICATOR LAMPS
The instrument cluster has warning lamps and
indicators for the following systems:
²Airbag
²Anti-lock Brakes (ABS) if equipped
²Brake warning
²Charging System²Front fog lamps (if equipped)
²High beam indicator
²Low fuel (premium cluster only)
²Low oil pressure
²Malfunction indicator (service engine soon) lamp
²Right and left turn signals
²Seat belt warning
²Security system
²Trac-Off (ABS equipped vehicles only)
The instrument cluster has a Vacuum Fluorescent
(VF) display for the following systems:
²Cruise
²Door (ajar)
²Odometer
²Set (cruise)
²Trac
²Trip
DIAGNOSIS AND TESTING
AIRBAG WARNING SYSTEM
For testing of this system refer to Group 8M, Pas-
sive Restraint Systems.
BRAKE SYSTEM WARNING LAMP TEST
The brake warning lamp illuminates when the
parking brake is applied with ignition switch turned
to the ON position. The same lamp will also illumi-
nate if one of the two service brake systems fail the
when brake pedal is applied.
To test the system:
²As the ignition switch is turned to the start posi-
tion the lamp should light.
²Turn ignition switch to the ON position and
apply the parking brake. The lamp should light.
If lamp fails to light inspect for:
²A burned out lamp
²Loose, corroded or damaged socket
²A damaged circuit board
²A broken or disconnected wire at the switch
²Defective switch
To test the service brake warning system, refer to
Group 5, Brakes, Hydraulic System Control Valves.
INSTRUMENT CLUSTER LAMPS
Every time the vehicle is switched to the START/
RUN position, the cluster goes through a BULB
CHECK. This tests most of the indicator lamps and
Vacuum Fluorescent (VF) displays. If only one lamp
is out, remove the instrument cluster and replace the
defective bulb or Light Emitting Diode (LED). If
some or all of the lamps fail to light, refer to the
proper Body Diagnostics Procedures Manual.
8E - 2 INSTRUMENT PANEL SYSTEMSPL

ENGINE OIL SERVICE
WARNING: NEW OR USED ENGINE OIL CAN BE
IRRITATING TO THE SKIN. AVOID PROLONGED OR
REPEATED SKIN CONTACT WITH ENGINE OIL.
CONTAMINANTS IN USED ENGINE OIL, CAUSED BY
INTERNAL COMBUSTION, CAN BE HAZARDOUS TO
YOUR HEALTH. THOROUGHLY WASH EXPOSED
SKIN WITH SOAP AND WATER. DO NOT WASH
SKIN WITH GASOLINE, DIESEL FUEL, THINNER, OR
SOLVENTS, HEALTH PROBLEMS CAN RESULT. DO
NOT POLLUTE, DISPOSE OF USED ENGINE OIL
PROPERLY. CONTACT YOUR DEALER OR GOVERN-
MENT AGENCY FOR LOCATION OF COLLECTION
CENTER IN YOUR AREA.
ENGINE OIL SPECIFICATION
CAUTION: Do not use non-detergent or straight
mineral oil when adding or changing crankcase
lubricant. Engine failure can result.
API SERVICE GRADE CERTIFIED
Use an engine oil that is API Service Grade Certi-
fied. MOPARtprovides engine oils that conforms to
this service grade.
SAE VISCOSITY
An SAE viscosity grade is used to specify the vis-
cosity of engine oil. Use only, engine oils with multi-
ple viscosities such as 5W-30 or 10W-30. These are
specified with a dual SAE viscosity grade which indi-
cates the cold-to-hot temperature viscosity range.
SAE 5W-30 engine oil is preferred. Select an engine
oil that is best suited to your particular temperature
range and variation (Fig. 9).
ENERGY CONSERVING OIL
An Energy Conserving type oil is recommended for
gasoline engines. The designation of ENERGY CON-
SERVING is located on the label of the engine oil
container.
CONTAINER IDENTIFICATION
Standard engine oil identification notations have
been adopted to aid in the proper selection of engine
oil. The identifying notations are located on the label
of engine oil plastic bottles and the top of engine oil
cans (Fig. 10).
ENGINE OIL CHANGE
Change engine oil at mileage and time intervals
described in the Group 0, Lubrication and Mainte-
nance.TO CHANGE ENGINE OIL
Run engine until achieving normal operating tem-
perature.
(1) Position the vehicle on a level surface and turn
engine off.
(2) Hoist and support vehicle on safety stands.
Refer to Group 0, Lubrication and Maintenance for
Hoisting and Jacking Recommendations.
(3) Remove oil fill cap.
(4) Place a suitable drain pan under crankcase
drain.
(5) Remove drain plug from crankcase and allow
oil to drain into pan. Inspect drain plug threads for
stretching or other damage. Replace drain plug and
gasket if damaged.
(6) Install drain plug in crankcase.
(7) Lower vehicle and fill crankcase with specified
type and amount of engine oil described in this sec-
tion.
(8) Install oil fill cap.
(9) Start engine and inspect for leaks.
(10) Stop engine and inspect oil level.
Fig. 9 Temperature/Engine Oil Viscosity
Fig. 10 Engine Oil Container Standard Notations
PLENGINE 9 - 7
GENERAL INFORMATION (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)

position of the throttle blade changes, the resistance
of the TPS changes.
OPERATION
The PCM supplies approximately 5 volts DC to the
TPS. The TPS output voltage (input signal to the
powertrain control module) represents throttle blade
position. The TPS output voltage to the PCM varies
from approximately 0.35 to 1.03 volts at minimum
throttle opening (idle) to a maximum of 3.1 to 4.0
volts at wide open throttle.
Along with inputs from other sensors, the PCM
uses the TPS input to determine current engine oper-
ating conditions. The PCM also adjusts fuel injector
pulse width and ignition timing based on these
inputs.
When the TPS indicates a voltage that is too high,
too low or not believable, the PCM sets a DTC. When
the DTC is set, the MIL is illuminated and the PCM
moves into limp-in mode. Limp-in for the TPS is
divided into three categories:
²Idle
²Part-throttle
²Wide open throttle (WOT)
VEHICLE SPEED SIGNAL (VSS)ÐPCM INPUT
DESCRIPTION
The PCM requires the VSS to be able to control
the following programs:
²Speed Control
²IAC motor (during deceleration)
²Injection pulse width (during deceleration)
²OBD II diagnostics
²PCM mileage EEPROM
²Road speed shutdown
²Speedometer/Odometer (bused message)NOTE: Road Speed Shutdown is the PCM shutting
off fuel injectors above a preset vehicle speed.
The vehicle speed sensor is located in the transmis-
sion extension housing (Fig. 21) and (Fig. 22).
OPERATION
The vehicle speed sensor on 3 speed automatic and
manual transaxle vehicles is a Hall-effect sensor.
This sensor is mechanically driven by a pinion gear
that is in mesh with the right axle drive shaft. The
hall-effect sensor switches a 5 volt signal sent from
the PCM from a ground to an open circuit.
Fig. 20 Throttle Position Sensor and Idle Air Control
Motor
Fig. 21 Vehicle Speed SensorÐAutomatic
Transmission
1 ± TRANSAXLE EXTENSION HOUSING
2 ± VEHICLE SPEED SENSOR
Fig. 22 Vehicle Speed SensorÐManual
Transmission
1 ± TRANSAXLE
2 ± SPEED SENSOR
3 ± SPEED SENSOR RETAINING BOLT
PLFUEL SYSTEM 14 - 37
DESCRIPTION AND OPERATION (Continued)