sensor DODGE NEON 1999 Service Owner's Guide

performed at each (- ground) connection in this cir-
cuit to locate the excessive resistance.
(7) Testing (+ positive) circuitry:
(a) Touch the positive lead of voltmeter directly
to battery negativePOST.
(b) Touch the negative lead of voltmeter to the
ground terminal stud on the generator case (not
the terminal mounting nut). Voltage should be no
higher than 0.3 volts. If voltage is higher than 0.3
volts, touch test lead to terminal mounting stud
nut and then to the wiring connector. If voltage is
now below 0.3 volts, look for dirty, loose or poor
connection at this point. A voltage drop test may be
performed at each (+ positive) connection in this
circuit to locate the excessive resistance. This test
can also be performed between the generator case
and the engine. If test voltage is higher than 0.3
volts, check for corrosion at generator mounting
points or loose generator mounting.
CURRENT OUTPUT TEST
The current output test will determine if the
charging system can deliver its minimum test cur-
rent (amperage) output. Refer to the Specifications
section at the end of this group for minimum test
current (amperage) requirements.
The first part of this test will determine the com-
bined amperage output of both the generator and the
Electronic Voltage Regulator (EVR) circuitry.
PREPARATION
(1) Determine if any Diagnostic Trouble Codes
(DTC) exist. To determine a DTC, refer to On-Board
Diagnostics in this group. For repair, refer to the
appropriate Powertrain Diagnostic Procedures man-
ual.
(2) Before starting test, make sure battery is in
good condition and is fully-charged. See Group 8A,
Battery for more information.
(3) Check condition of battery cables at battery.
Clean if necessary.
(4) Perform the Voltage Drop Test. This will
ensure clean and tight generator/battery electrical
connections.
(5) Be sure the generator drive belt is properly
tensioned. Refer to Group 7, Cooling System for
information.
(6) A volt/amp tester equipped with both a battery
load control (carbon pile rheostat) and an inductive-
type pickup clamp (ammeter probe) will be used for
this test. Refer to operating instructions supplied
with tester. When using a tester equipped with an
inductive-type clamp, removal of wiring at the gener-
ator will not be necessary.
(7) Start the engine and allow it to reach operating
temperature.
(8) Shut engine off.(9) Turn off all electrical accessories and all vehicle
lighting.
(10) Connect the volt/amp tester leads to the bat-
tery. Be sure the carbon pile rheostat control is in the
OPEN or OFF position before connecting leads. See
Load Test in Group 8A, Battery for more information.
Also refer to the operating instructions supplied with
test equipment.
(11) Connect the inductive clamp (ammeter probe).
Refer to the operating instructions supplied with test
equipment.
(12) If volt/amp tester is not equipped with an
engine tachometer, connect a separate tachometer to
the engine.
TEST
(1) Perform the previous test Preparation.
(2) Fully engage the parking brake.
(3) Start engine.
(4) Bring engine speed to 2500 rpm.
(5) With engine speed held at 2500 rpm, slowly
adjust the rheostat control (load) on the tester to
obtain the highest amperage reading. Do not allow
voltage to drop below 12 volts. Record the reading.
This load test must be performed within 15 sec-
onds to prevent damage to test equipment.On
certain brands of test equipment, this load will be
applied automatically. Refer to the operating manual
supplied with test equipment.
(6) The ammeter reading must meet the Minimum
Test Amps specifications as displayed in the Genera-
tor Ratings chart. This can be found in the Specifica-
tions section at the end of this group. A label stating
a part reference number is attached to the generator
case. On some engines this label may be located on
the bottom of the case. Compare this reference num-
ber to the Generator Ratings chart.
(7) Rotate the load control to the OFF position.
(8) Continue holding engine speed at 2500. If EVR
circuitry is OK, amperage should drop below 15±20
amps. With all electrical accessories and vehicle
lighting off, this could take several minutes of engine
operation. If amperage did not drop, refer to the
appropriate Powertrain Diagnostic Procedures man-
ual for testing.
(9) Remove volt/amp tester.
If minimum amperage could not be met, refer to
the appropriate Powertrain Diagnostic Procedures
manual for testing.
BATTERY TEMPERATURE SENSOR
To perform a complete test of this sensor and its
circuitry, refer to the appropriate Powertrain Diag-
nostic Procedures manual. To test the sensor only,
refer to the following:
(1) The sensor is located under the battery and is
attached to the battery tray (Fig. 5). A two-wire pig-
8C - 8 CHARGING SYSTEMPL
DIAGNOSIS AND TESTING (Continued)

tail harness is attached directly to the sensor. The
opposite end of this harness connects the sensor to
the engine wiring harness.
(2) Disconnect the two-wire pigtail harness from
the engine harness.
(3) Attach ohmmeter leads to the wire terminals of
the pigtail harness.
(4) At room temperature of 25É C (75±80É F), an
ohmmeter reading of 9,000 (9K) to 11,000 (11K) ohms
should be observed.
(5) If reading is above or below the specification,
replace the sensor.
(6) Refer to the Removal and Installation section
for procedures.
ON-BOARD DIAGNOSTIC SYSTEM TEST
GENERAL INFORMATION
The Powertrain Control Module (PCM) monitors
critical input and output circuits of the charging sys-
tem, making sure they are operational. A Diagnostic
Trouble Code (DTC) is assigned to each input and
output circuit monitored by the OBD system. Some
circuits are checked continuously and some are
checked only under certain conditions.
If the OBD system senses that a monitored circuit
is bad, it will put a DTC into electronic memory. The
DTC will stay in electronic memory as long as the
circuit continues to be bad. The PCM is programmed
to clear the memory after 50 engine starts if the
problem does not occur again.
DIAGNOSTIC TROUBLE CODES
Refer to Group 25, On Board Diagnostic for more
information. A DTC description can be read using the
DRB scan tool. Refer to the appropriate Powertrain
Diagnostic Procedures manual for information.
A DTC does not identify which component in a cir-
cuit is bad. Thus, a DTC should be treated as asymptom, not as the cause for the problem. In some
cases, because of the design of the diagnostic test
procedure, a DTC can be the reason for another DTC
to be set. Therefore, it is important that the test pro-
cedures be followed in sequence, to understand what
caused a DTC to be set.
ERASING DIAGNOSTIC TROUBLE CODES
The DRB Scan Tool must be used to erase a DTC.
REMOVAL AND INSTALLATION
GENERATOR
REMOVAL
(1) Disconnect battery negative cable (Fig. 6).
(2) Loosen but DO NOT remove the generator
adjustment nut.
(3) Raise vehicle with front wheels turned fully to
the right.
(4) Remove the plastic lower splash shield.
(5) Disconnect the generator field circuit wiring
connector (Fig. 9). Squeeze locking tab to release.
(6) Remove the B+ terminal nut and wire.
(7) Loosen pivot bolt, but do not remove (Fig. 8)
and (Fig. 9).
(8) Remove the generator drive belt. The generator
spill shield does not need to be removed.
(9) Remove three mounting pivot bracket bolts.
(10) Remove pivot bolt and bracket.
(11) Holding the generator in one hand, remove
adjustment nut and slide the generator off the T-bolt.
The T-bolt does not need to be removed.
(12) Lower the generator and remove through the
wheel well.
INSTALLATION
(1) For installation, reverse above procedures. The
generator field connector has a locking tab and will
snap when fully installed. Refer to group 7 Cooling
System, Belt Removal/Install Adjust. Tighten all fas-
teners to the proper torque. Refer to the Torque Spec-
Fig. 5 Battery Temperature Sensor
Fig. 6 Removal/Installation of Battery Cables
8C - 10 CHARGING SYSTEMPL
DIAGNOSIS AND TESTING (Continued)

ifications chart in Group 8A, Battery/Starter/
Charging Systems Diagnostics.
BATTERY TEMPERATURE SENSOR
REMOVAL
(1) Make sure ignition switch is in OFF position
and all accessories are OFF.
(2) Remove battery negative cable first then the
positive cable (Fig. 10).
Fig. 7 Wire Terminal Connection
Fig. 8 Generator Front View
Fig. 9 Generator Rear View
Fig. 10 Removal of Battery Cables
PLCHARGING SYSTEM 8C - 11
REMOVAL AND INSTALLATION (Continued)

(3) Remove battery thermoguard (Fig. 11).
WARNING: TO PROTECT THE HANDS FROM BAT-
TERY ACID, A SUITABLE PAIR OF HEAVY DUTY
RUBBER GLOVES, NOT THE HOUSEHOLD TYPE,
SHOULD BE WORN WHEN REMOVING OR SERVIC-
ING A BATTERY. SAFETY GLASSES ALSO SHOULD
BE WORN.
(4) Remove temperature sensor mounting nut from
battery tray (Fig. 12).
(5) Disconnect sensor wire connector (Fig. 13).
INSTALLATION
For installation reverse above procedures.
SPECIFICATIONS
GENERATOR RATINGS
TORQUE
DESCRIPTION TORQUE
Battery Terminal Nut..........9N´m(75in.lbs.)
Battery Hold Down Clamp Bolt . . .9 N´m (75 in. lbs.)
Generator Mounting Bolt.......54N´m(40ft.lbs.)
Generator Pivot Bolt...........54N´m(40ft.lbs.)
TYPE PART NUMBER RATED SAE AMPS ENGINES MINIMUM TEST AMPS
MELCO 4793190 83 AMPS 2.0L SOHC/DOHC 75 AMPS
Fig. 11 Battery Thermoguard
Fig. 12 Battery Temperature Sensor Location
Fig. 13 Battery Temperature Sensor Connector
8C - 12 CHARGING SYSTEMPL
REMOVAL AND INSTALLATION (Continued)

IGNITION SYSTEM
CONTENTS
page page
GENERAL INFORMATION
INTRODUCTION......................... 1
DESCRIPTION AND OPERATION
AUTOMATIC SHUTDOWN RELAY............ 3
CAMSHAFT POSITION SENSOR............. 4
COMBINATION ENGINE COOLANT
TEMPERATURE SENSOR................. 5
CRANKSHAFT POSITION SENSOR........... 4
ELECTRONIC IGNITION COILS.............. 3
IGNITION INTERLOCK.................... 7
IGNITION SWITCH....................... 7
IGNITION SYSTEM....................... 1
INTAKE AIR TEMPERATURE SENSOR........ 6
KNOCK SENSOR......................... 6
LOCK KEY CYLINDER..................... 7
MANIFOLD ABSOLUTE PRESSURE SENSOR
(MAP)............................... 6
POWERTRAIN CONTROL MODULE.......... 2
SPARK PLUG CABLES.................... 2
SPARK PLUGS.......................... 2
THROTTLE POSITION SENSOR (TPS)........ 6
DIAGNOSIS AND TESTING
CAMSHAFT POSITION SENSOR AND
CRANKSHAFT POSITION SENSOR......... 9
CHECK COIL TEST....................... 8
ENGINE COOLANT TEMPERATURE SENSOR . . . 9
FAILURE TO START TESTÐ2.0/2.4L......... 8
IGNITION TIMING PROCEDURE............. 9
INTAKE AIR TEMPERATURE SENSOR........ 9
MANIFOLD ABSOLUTE PRESSURE (MAP)
SENSOR TEST......................... 9
SPARK PLUG CONDITION................ 10TESTING FOR SPARK AT COILÐ2.0/2.4L..... 7
THROTTLE POSITION SENSOR............. 9
REMOVAL AND INSTALLATION
AUTOMATIC SHUTDOWN RELAY........... 13
CAMSHAFT POSITION SENSORÐDOHC..... 14
CAMSHAFT POSITION SENSORÐSOHC..... 13
COMBINATION ENGINE COOLANT
TEMPERATURE SENSORÐDOHC........ 15
COMBINATION ENGINE COOLANT
TEMPERATURE SENSORÐSOHC......... 15
CRANKSHAFT POSITION SENSOR.......... 15
IGNITION COIL......................... 13
IGNITION INTERLOCK................... 18
IGNITION SWITCH...................... 16
LOCK CYLINDER HOUSING............... 18
LOCK KEY CYLINDER.................... 17
MAP/IAT SENSORÐDOHC................ 16
MAP/IAT SENSORÐSOHC................ 16
POWERTRAIN CONTROL MODULE (PCM) . . . 12
SPARK PLUG CABLE SERVICE............ 13
SPARK PLUG SERVICE.................. 12
SPARK PLUG TUBES.................... 13
THROTTLE POSITION SENSOR............ 16
SPECIFICATIONS
FIRING ORDERÐ2.0L................... 18
IGNITION COIL......................... 19
SPARK PLUG CABLE RESISTANCEÐDOHC . . 18
SPARK PLUG CABLE RESISTANCEÐSOHC . . . 18
SPARK PLUG.......................... 19
TORQUE SPECIFICATION................. 18
VECI LABEL........................... 18
GENERAL INFORMATION
INTRODUCTION
This section describes the electronic ignition sys-
tem for the 2.0L engines used in Neon vehicles.
The On-Board Diagnostics Section in Group 25
describes diagnostic trouble codes.
Group 0, Lubrication and Maintenance, contains
general maintenance information for ignition relateditems. The Owner's Manual also contains mainte-
nance information.DESCRIPTION AND OPERATION
IGNITION SYSTEM
Ignition system operation and diagnostics, are
identical for 2.0L Single Overhead Cam (SOHC) and
2.0L Duel Overhead Cam (DOHC) engines.
PLIGNITION SYSTEM 8D - 1

The major difference between the two engines is
component location which affects the ignition system
service procedures. There are various sensors that
are in different locations due to a different cylinder
head and intake manifold.
The 2.0L engines use a fixed ignition timing sys-
tem. The distributorless electronic ignition system is
referred to as the Direct Ignition System (DIS).
Basic ignition timing is not adjustable.The
Powertrain Control Module (PCM) determines spark
advance. The system's three main components are
the coil pack, crankshaft position sensor, and cam-
shaft position sensor.
POWERTRAIN CONTROL MODULE
The Powertrain Control Module (PCM) controls the
ignition system (Fig. 1). The PCM supplies battery
voltage to the ignition coil through the Auto Shut-
down (ASD) Relay. The PCM also controls the ground
circuit for the ignition coil. By switching the ground
path for the coil on and off, the PCM adjusts ignition
timing to meet changing engine operating conditions.
During the crank-start period the PCM maintains
spark advance at 9É BTDC. During engine operation
the following inputs determine the amount of spark
advance provided by the PCM.
²Intake air temperature
²Coolant temperature
²Engine RPM
²Intake manifold vacuum
²Knock sensor
The PCM also regulates the fuel injection system.
Refer to the Fuel Injection sections of Group 14.
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.
Replace spark plugs at the intervals recommended in
Group 0.
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. After
cleaning, file the center electrode flat with a small
point file or jewelers file. Adjust the gap between the
electrodes (Fig. 2) to the dimensions specified in the
chart at the end of this section.
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.
Loose cable connections will corrode, increase resis-
tance and permit water to enter the coil towers.
These conditions can cause ignition malfunction.
Fig. 1 Powertrain Control Module
Fig. 2 Setting Spark Plug Electrode Gap
8D - 2 IGNITION SYSTEMPL
DESCRIPTION AND OPERATION (Continued)

Plastic clips in various locations protect the cables
from damage. When the cables are replaced the clips
must be used to prevent damage to the cables. The
#1 cable must be routed under the PCV hose and
clipped to the #2 cable.
ELECTRONIC IGNITION COILS
WARNING: THE DIRECT IGNITION SYSTEM GEN-
ERATES APPROXIMATELY 40,000 VOLTS. PER-
SONAL INJURY COULD RESULT FROM CONTACT
WITH THIS SYSTEM.
The coil pack consists of 2 coils molded together.
The coil pack is mounted on the valve cover (Fig. 3)
or (Fig. 4). High tension leads route to each cylinder
from the coil. The coil fires two spark plugs every
power stroke. One plug is the cylinder under com-
pression, the other cylinder fires on the exhaust
stroke. Coil number one fires cylinders 1 and 4. Coil
number two fires cylinders 2 and 3. The PCM deter-
mines which of the coils to charge and fire at the cor-
rect time.
The Auto Shutdown (ASD) relay provides battery
voltage to the ignition coil. The PCM provides a
ground contact (circuit) for energizing the coil. When
the PCM breaks the contact, the energy in the coil
primary transfers to the secondary causing the
spark. The PCM will de-energize the ASD relay if it
does not receive the crankshaft position sensor and
camshaft position sensor inputs. Refer to Auto Shut-
down (ASD) RelayÐPCM Output, in this section for
relay operation.
AUTOMATIC SHUTDOWN RELAY
The Automatic Shutdown (ASD) relay supplies bat-
tery voltage to the fuel injectors, electronic ignition
coil and the heating elements in the oxygen sensors.
A buss bar in the Power Distribution Center (PDC)
supplies voltage to the solenoid side and contact sideof the relay. The ASD relay power circuit contains a
20 amp fuse between the buss bar in the PDC and
the relay. The fuse also protects the power circuit for
the fuel pump relay and pump. The fuse is located in
the PDC. Refer to Group 8W, Wiring Diagrams for
circuit information.
The PCM controls the ASD relay by switching 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 igni-
tion switch is in On or Start, the PCM monitors the
crankshaft and camshaft position sensor signals to
determine engine speed and ignition timing (coil
dwell). If the PCM does not receive crankshaft and
camshaft position sensor signals when the ignition
switch is in the Run position, it will de-energize the
ASD relay.
The ASD relay is located in the PDC (Fig. 5). The
inside top of the PDC cover has label showing relay
and fuse identification.
Fig. 3 Ignition Coil PackÐSOHC
Fig. 4 Ignition Coil PackÐDOHC
Fig. 5 Power Distribution Center (PDC)
PLIGNITION SYSTEM 8D - 3
DESCRIPTION AND OPERATION (Continued)

CRANKSHAFT POSITION SENSOR
The PCM determines what cylinder to fire from the
crankshaft position sensor input and the camshaft
position sensor input. The second crankshaft counter-
weight has machined into it two sets of four timing
reference notches including a 60 degree signature
notch (Fig. 6). From the crankshaft position sensor
input the PCM determines engine speed and crank-
shaft angle (position).
The notches generate pulses from high to low in
the crankshaft position sensor output voltage. When
a metal portion of the counterweight aligns with the
crankshaft position sensor, the sensor output voltage
goes low (less than 0.5 volts). When a notch aligns
with the sensor, voltage goes high (5.0 volts). As a
group of notches pass under the sensor, the output
voltage switches from low (metal) to high (notch)
then back to low.
If available, an oscilloscope can display the square
wave patterns of each voltage pulse. From the fre-
quency of the output voltage pulses, the PCM calcu-
lates engine speed. The width of the pulses represent
the amount of time the output voltage stays high
before switching back to low. The period of time the
sensor output voltage stays high before switching
back to low is referred to as pulse-width. The faster
the engine is operating, the smaller the pulse-width
on the oscilloscope.
By counting the pulses and referencing the pulse
from the 60 degree signature notch, the PCM calcu-
lates crankshaft angle (position). In each group of
timing reference notches, the first notch represents
69 degrees before top dead center (BTDC). The sec-
ond notch represents 49 degrees BTDC. The third
notch represents 29 degrees. The last notch in eachset represents 9 degrees before top dead center
BTDC.
The timing reference notches are machined at 20É
increments. From the voltage pulse-width the PCM
tells the difference between the timing reference
notches and the 60 degree signature notch. The 60
degree signature notch produces a longer pulse-width
than the smaller timing reference notches. If the
camshaft position sensor input switches from high to
low when the 60 degree signature notch passes under
the crankshaft position sensor, the PCM knows cylin-
der number one is the next cylinder at TDC.
The crankshaft position sensor mounts to the
engine block behind the generator, just above the oil
filter (Fig. 7).
CAMSHAFT POSITION SENSOR
The PCM determines fuel injection synchronization
and cylinder identification from inputs provided by
Fig. 6 Timing Reference Notches
Fig. 7 Crankshaft Position Sensor
8D - 4 IGNITION SYSTEMPL
DESCRIPTION AND OPERATION (Continued)

the camshaft position sensor (Fig. 8) or (Fig. 9) and
crankshaft position sensor. From the two inputs, the
PCM determines crankshaft position.
The camshaft position sensor attaches to the rear
of the cylinder head (Fig. 10). A target magnet
attaches to the rear of the camshaft and indexes to
the correct position. The target magnet has four dif-
ferent poles arranged in an asymmetrical pattern. As
the target magnet rotates, the camshaft position sen-
sor senses the change in polarity (Fig. 11). The sen-
sor input switches from high (5 volts) to low (0.30
volts) as the target magnet rotates. When the north
pole of the target magnet passes under the sensor,
the output switches high. The sensor output switches
low when the south pole of the target magnet passes
underneath.
The camshaft position sensor is mounted to the
rear of the cylinder head. The sensor also acts as a
thrust plate to control camshaft endplay on SOHC
engines.
COMBINATION ENGINE COOLANT TEMPERATURE
SENSOR
The coolant temperature sensor provides an input
voltage to the PCM and a separate input voltage to
the temperature gauge on the instrument panel. The
PCM determines engine coolant temperature from
the coolant temperature sensor. As coolant tempera-
ture varies, the coolant temperature sensor resis-
tance changes resulting in a different input voltage
to the PCM.
When the engine is cold, the PCM will demand
slightly richer air-fuel mixtures and higher idle
speeds until normal operating temperatures are
reached.
Fig. 8 Camshaft Position SensorÐSOHC
Fig. 9 Camshaft Position SensorÐDOHC
Fig. 10 Target Magnet ÐTypical
Fig. 11 Target Magnet Polarity
PLIGNITION SYSTEM 8D - 5
DESCRIPTION AND OPERATION (Continued)

SOHC
The coolant sensor threads into the end of the cyl-
inder head, next to the camshaft position sensor (Fig.
12). New sensors have sealant applied to the threads.
DOHC
The coolant sensor threads into the intake mani-
fold next to the thermostat housing (Fig. 13). New
sensors have sealant applied to the threads.
INTAKE AIR TEMPERATURE SENSOR
The intake air temperature sensor measures the
temperature of the air as it enters the engine. The
sensor supplies one of the inputs the PCM uses to
determine injector pulse-width.
The MAP/Intake Air Temperature (IAT) sensor,
located on the intake manifold, combines the MAP
and Intake Air Temperature (IAT) functions into one
sensor (Fig. 14) or (Fig. 15).
KNOCK SENSOR
The knock sensor threads into the side of the cyl-
inder block in front of the starter motor. When the
knock sensor detects a knock in one of the cylinders,
it sends an input signal to the PCM. In response, the
PCM retards ignition timing for all cylinders by a
scheduled amount.
Knock sensors contain a piezoelectric material
which constantly vibrates and sends an input voltage
(signal) to the PCM while the engine operates. As the
intensity of the crystal's vibration increase, the knock
sensor output voltage also increases.
NOTE: Over or under tightening effects knock sen-
sor performance, possibly causing improper spark
control.
MANIFOLD ABSOLUTE PRESSURE SENSOR (MAP)
The PCM supplies 5 volts to the MAP sensor. The
MAP sensor function converts intake manifold pres-
sure into voltage. The PCM monitors the MAP sensor
output voltage. As vacuum increases, MAP sensor
voltage decreases proportionately. Also, as vacuum
decreases, MAP sensor voltage increases proportion-
ately.
Key on, before the engine starts running, the PCM
determines atmospheric air pressure from the MAP
sensor voltage. While the engine operates, the PCM
determines intake manifold pressure from the MAP
sensor voltage. Based on MAP sensor voltage and
inputs from other sensors, the PCM adjusts spark
advance and the air/fuel mixture.
The MAP/IAT sensor mounts to the intake mani-
fold (Fig. 14) or (Fig. 15).
THROTTLE POSITION SENSOR (TPS)
The TPS mounts to the side of the throttle body.
The TPS connects to the throttle blade shaft. The
TPS is a variable resistor that provides the Power-
Fig. 12 Engine Coolant Temperature SensorÐSOHC
Fig. 13 Engine Coolant Temperature SensorÐDOHC
Fig. 14 MAP/IAT sensorÐSOHC
8D - 6 IGNITION SYSTEMPL
DESCRIPTION AND OPERATION (Continued)