engine DODGE NEON 1999 Service Repair Manual

FUEL INJECTORSÐPCM OUTPUT
The 2.0L engine uses electrically operated top feed
fuel injectors (Fig. 26). The Automatic Shutdown
(ASD) relay supplies battery voltage to the fuel injec-
tors. The PCM controls the ground path for each
injector in sequence. By switching the ground paths
on and off, the PCM fine-tunes injector pulse width.
Injector pulse width refers to the amount of time an
injector operates.
The PCM determines injector synchronization from
the camshaft position sensor and crankshaft position
sensor inputs. The PCM grounds the ASD and fuel
pump relays after receiving the camshaft position
sensor and crankshaft position sensor inputs.
The PCM energizes the injectors in a sequential
order during all engine operating conditions except
start-up. For the first injector pulse width during
start-up, all injectors are energized at the same time.
Once the PCM determines crankshaft position, it
begins energizing the injectors in sequence.
IGNITION COILÐPCM OUTPUT
The coil assembly consists of 2 coils molded
together. The coil assembly is mounted over the valve
cover (Fig. 27) or (Fig. 28). High tension leads route
to each cylinder from the coil. The coil fires two
spark plugs every power stroke. One plug is the cyl-
inder under compression, 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 determines which of the coils to charge and fire
at the correct 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 andcamshaft position sensor inputs. Refer to Auto Shut-
down (ASD) RelayÐPCM Output in this section for
relay operation.
MALFUNCTION INDICATOR (CHECK ENGINE)
LAMPÐPCM OUTPUT
The PCM supplies the malfunction indicator (check
engine) lamp on/off signal to the instrument panel
through the CCD Bus. The CCD Bus is a communi-
cations port. Various modules use the CCD Bus to
exchange information.
The Check Engine lamp comes on each time the
ignition key is turned ON and stays on for 3 seconds
as a bulb test.
The Malfunction Indicator Lamp (MIL) stays on
continuously, when the PCM has entered a Limp-In
mode or identified a failed emission component. Dur-
ing Limp-in Mode, the PCM attempts to keep the
system operational. The MIL signals the need for
immediate service. In limp-in mode, the PCM com-
pensates for the failure of certain components that
Fig. 26 Fuel Injector
Fig. 27 Ignition Coil PackÐSOHC
Fig. 28 Ignition Coil PackÐDOHC
14 - 34 FUEL SYSTEMPL
DESCRIPTION AND OPERATION (Continued)

send incorrect signals. The PCM substitutes for the
incorrect signals with inputs from other sensors.
If the PCM detects active engine misfire severe
enough to cause catalyst damage, it flashes the MIL.
At the same time the PCM also sets a Diagnostic
Trouble Code (DTC).
For signals that can trigger the MIL (Check
Engine Lamp) refer to Group 25, On-Board
Dianostics.
SOLID STATE FAN RELAYÐPCM OUTPUT
The radiator fan runs when coolant temperature
and A/C system pressure demand cooling. The radia-
tor fan circuit contains a Solid State Fan Relay
(SSFR). Refer to the Group 8W for a circuit sche-
matic.
A 5 volt signal is supplied to the SSFR. The PCM
provides a pulsed ground for the SSFR. Depending
upon the amount of pulse on time, the SSFR puts out
a proportional voltage to the fan motor at the lower
speed. For instance, if the on time is 30 percent, then
the voltage to the fan motor will be 3.6 volts.
When engine coolant reaches approximately 99ÉC
(210ÉF) the PCM grounds the SSFR relay. When the
PCM grounds the relay it operates at a 30% duty
cycle and immediately ramps up to 100% duty cycle.
The PCM de-energizes the SSFR relay when coolant
temperature drops to approximately 93ÉC (199ÉF).
Also, when the air conditioning pressure switch
closes, the PCM grounds the SSFR. The air condi-
tioning switch closes at 285 psi610 psi. When air
conditioning pressure drops approximately 40 psi, the
pressure switch opens and the fan turns off.
The SSFR relay is located on the left front inner
frame just behind the radiator.
SPEED CONTROLÐPCM INPUT
The speed control system provides five separate
voltages (inputs) to the Powertrain Control Module
(PCM). The voltages correspond to the ON/OFF, SET,
RESUME and CANCEL.
The speed control ON voltage informs the PCM
that the speed control system has been activated.
The speed control SET voltage informs the PCM that
a fixed vehicle speed has been selected. The speed
control RESUME voltage indicates the previous fixed
speed is requested. The speed control CANCEL volt-
age tells the PCM to deactivate but retain set speed
in memory (same as depressing the brake pedal). The
speed control OFF voltage tells the PCM that the
speed control system has deactivated. Refer to Group
8H for more speed control information.
SCI RECEIVEÐPCM OUTPUT
SCI Receive is the serial data communication
receive circuit for the DRB scan tool. The Powertrain
Control Module (PCM) receives data from the DRB
through the SCI Receive circuit.
TACHOMETERÐPCM OUTPUT
The PCM operates the tachometer on the instru-
ment panel. The PCM calculates engine RPM from
the crankshaft position sensor input.
TORQUE CONVERTOR CLUTCH SOLENOIDÐPCM
OUTPUT
Three-speed automatic transaxles use a torque con-
verter clutch solenoid. The PCM controls the engage-
ment of the torque converter clutch through the
solenoid (Fig. 29). The torque converter clutch is
engaged up only in direct drive mode. Refer to Group
21 for transmission information.
DIAGNOSIS AND TESTING
VISUAL INSPECTIONÐSOHC
Before diagnosing or servicing the fuel injection
system, perform a visual inspection for loose, discon-
nected, or misrouted wires and hoses (Fig. 30). A
thorough visual inspection that includes the following
checks saves unnecessary test and diagnostic time.
(1) Inspect the battery connections. Clean corroded
terminals (Fig. 31).
(2) Check the 2 PCM 40-way connector for
stretched wires on pushed out terminals (Fig. 31).
Fig. 29 Torque Convertor Clutch Solenoid
PLFUEL SYSTEM 14 - 35
DESCRIPTION AND OPERATION (Continued)

(3) Open the Power Distribution Center (PDC).
Check for blown fuses. Ensure the relays and fuses
are fully seated in the PDC (Fig. 32). A label on the
underside of the PDC cover shows the locations of
each relay and fuse.
(4) Verify the throttle cable operates freely (Fig.
33).
(5) Check the electrical connections at the idle air
control motor and throttle position sensor (Fig. 34).
(6) Check hose connections between the PCV
valve, vacuum port - intake manifold and the oil sep-
arator (Fig. 35).
(7) Inspect the electrical connections at the MAP
sensor/intake air temperature sensor and the (Fig.
36).
(8) Inspect the fuel injector electrical connections
(Fig. 37).
(9) Inspect the ignition coil electrical connector.
Ensure the spark plug insulators are firmly seated
over the spark plugs (Fig. 38).
Fig. 30 2.0L SOHC Engine Compartment
Fig. 31 Battery, PCM, and PDC
Fig. 32 Power Distribution Center
Fig. 33 Throttle CableÐAutomatic Transmission
Fig. 34 Idle Air Control Motor and Throttle Position
SensorÐTypical
14 - 36 FUEL SYSTEMPL
DIAGNOSIS AND TESTING (Continued)

(14) Check the electrical connection at the knock
sensor (Fig. 41).
(15) Check the electrical connections at the cam-
shaft position sensor and engine coolant temperature
sensor (Fig. 42).
(16) Check the electrical connector at the Elec-
tronic EGR Transducer. Inspect the vacuum and back
pressure hoses at the solenoid and transducer for
leaks (Fig. 43).
(17) Inspect the electrical connections at the gen-
erator (Fig. 44). Check the generator belt for glazing
or damage.
Fig. 39 Duty Cycle Purge Solenoid
Fig. 40 Starter Motor and Ground Strap
Fig. 41 Knock Sensor
Fig. 42 Camshaft Position Sensor and Engine
Coolant Temperature Sensor
Fig. 43 Electronic EGR Transducer
14 - 38 FUEL SYSTEMPL
DIAGNOSIS AND TESTING (Continued)

VISUAL INSPECTIONÐDOHC
Before diagnosing or servicing the fuel injection
system, perform a visual inspection for loose, discon-
nected, or misrouted wires and hoses (Fig. 53). Athorough visual inspection that includes the following
checks saves unnecessary test and diagnostic time.
(1) Inspect the battery connections. Clean corroded
terminals (Fig. 31).
(2) Check the 2 PCM 40-way connector for
stretched wires on pushed out terminals (Fig. 54).
Fig. 49 Upstream Heated Oxygen Sensor
Fig. 50 Downstream Heated Oxygen Sensor
Fig. 51 Fuel Pump Module Electrical Connector
Fig. 52 Battery Temp. Sensor Connectors
Fig. 53 2.0L DOHC Engine Compartment
14 - 40 FUEL SYSTEMPL
DIAGNOSIS AND TESTING (Continued)

(13) Inspect the air cleaner filter element. Replace
as necessary. Check the air induction system for
restrictions.
(14) Check the electrical connection at the knock
sensor (Fig. 64).
(15) Check the electrical connections at the cam-
shaft position sensor (Fig. 65) and engine coolant
temperature sensor (Fig. 66).
(16) Check the electrical connector at the Elec-
tronic EGR Transducer. Inspect the vacuum and back
pressure hoses at the solenoid and transducer for
leaks (Fig. 67).
(17) Inspect the electrical connections at the gen-
erator (Fig. 68). Check the generator belt for glazing
or damage.
Fig. 63 Starter Motor and Ground Strap
Fig. 64 Knock Sensor
Fig. 65 Camshaft Position Sensor
Fig. 66 Engine Coolant Temperature Sensor
Fig. 67 Electronic EGR Transducer
PLFUEL SYSTEM 14 - 43
DIAGNOSIS AND TESTING (Continued)

(7) Attach the other end of the jumper wire to
relay terminal 86. This activates the relay. The ohm-
meter should now show continuity between relay ter-
minals 87 and 30. The ohmmeter should not show
continuity between relay terminals 87A and 30.
(8) Disconnect jumper wires.
(9) Replace the relay if it did not pass the continu-
ity and resistance tests. If the relay passed the tests,
it operates properly. Check the remainder of the ASD
and fuel pump relay circuits. Refer to group 8W, Wir-
ing Diagrams.
CAMSHAFT AND CRANKSHAFT POSITION SENSOR
Refer to Group 8D, Ignition for Diagnosis and Test-
ing of Camshaft and Crankshaft Sensors.
ENGINE COOLANT TEMPERATURE SENSOR
(1) With the key off, disconnect wire harness con-
nector from coolant temperature sensor (Fig. 79) or
(Fig. 80).(2) Connect a high input impedance (digital) volt-
ohmmeter to terminals A and B (Fig. 81). The ohm-
meter should read as follows:
²Engine/Sensor at normal operating temperature
around 200ÉF should read approximately 700 to
1,000 ohms.
²Engine/Sensor at room temperature around 70ÉF
ohmmeter should read approximately 7,000 to 13,000
ohms.
(3) T
est the resistance of the wire harness between
the PCM 60-way connector terminal 28 and the sensor
harness connector. Also check for continuity between
PCM 60-way connector terminal 51 and the sensor har-
ness connector. Refer to Group 8W, Wiring diagrams for
circuit information. If the resistance is greater than 1
ohm, repair the wire harness as necessary.
HEATED OXYGEN SENSOR
Use an ohmmeter to test the heating element of
the oxygen sensors. Disconnect the electrical connec-
tor from each oxygen sensor. The white wires in the
sensor connector are the power and ground circuits
for the heater. Connect the ohmmeter test leads to
terminals of the white wires in the heated oxygen
sensor connector. Replace the heated oxygen sensor if
the resistance is not between 4 and 7 ohms.
IDLE AIR CONTROL (IAC) MOTOR TEST
To preform a complete test of IAC motor and its
circuitry, refer to DRB scan tool and the appropriate
Powertrain Diagnostics Procedures manual.
KNOCK SENSOR
The engine knock sensor is affected by a number of
factors. A few of these are: ignition timing, cylinder
pressure, fuel octane, etc. The knock sensor generates
an AC voltage whose amplitude increases with the
increase of engine knock. The knock sensor can be
tested with a digital voltmeter. The RMS voltage starts
Fig. 79 Engine Coolant Temperature Sensor
LocationÐSOHC
Fig. 80 Engine Coolant Temperature Sensor
LocationÐDOHC
Fig. 81 Engine Coolant Temperature Sensor
PLFUEL SYSTEM 14 - 47
DIAGNOSIS AND TESTING (Continued)

at about 20mVac (at about 700 rpm) and increases to
approximately 600 mVac (5000 rpm). If the output falls
outside of this range a DTC will be set.
MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR
To perform a complete test of the MAP sensor and
its circuitry, refer to the DRB scan tool and appropri-
ate Powertrain Diagnostics Procedures manual. To
test the MAP sensor only, refer to the following:
CAUTION: When testing the MAP sensor, be sure
that the harness wires are not damaged by the test
meter probes.
(1) Test the MAP sensor output voltage at the
MAP sensor connector between terminals 1 and 4
(Fig. 82). With the ignition switch ON and the engine
not running, output voltage should be 4 to 5 volts.
The voltage should drop to 1.5 to 2.1 volts with a hot,
neutral idle speed condition. If OK, go to next step. If
not OK, go to step 3.
(2) Test PCM terminal 36 for the same voltage
described in the previous step to verify wire harness
condition. Repair as required.
(3) Test the MAP sensor ground circuit at sensor
connector terminal 1 and PCM terminal 43. If OK, go
to next step. If not OK, repair as required.
(4) Test MAP sensor supply voltage between sen-
sor connector terminals 3 and 1 with the key ON.
The voltage should be approximately 5 volts (6.5V).
Five volts (6.5V) should also be at terminal 61 of the
PCM. If OK, replace MAP sensor. If not OK, repair or
replace the wire harness as required.
THROTTLE POSITION SENSOR
To perform a complete test of the this sensor and
its circuitry, refer to the DRB scan tool and appropri-
ate Powertrain Diagnostics Procedures manual. To
test the throttle position sensor only, refer to the fol-
lowing:
The Throttle Position Sensor (TPS) can be tested
with a digital voltmeter (DVM). The center terminal
of the sensor is the output terminal. One of the other
terminals is a 5 volt supply and the remaining ter-
minal is ground.
Connect the DVM between the center and sensor
ground terminal. Refer to Group 8W - Wiring Dia-
grams for correct pinout.
With the ignition switch in the ON position, check
the output voltage at the center terminal wire of the
connector. Check the output voltage at idle and at
Wide-Open-Throttle (WOT). At idle, TPS output volt-
age should be approximately 0.38 volts to 1.2 volts.
At wide open throttle, TPS output voltage should be
approximately 3.1 volts to 4.4 volts. The output volt-
age should gradually increase as the throttle plate
moves slowly from idle to WOT.
Check for spread terminals at the sensor and PCM
connections before replacing the TPS.
THROTTLE BODY MINIMUM AIR FLOW
(1) Turn ignition key to Off.
(2) Disconnect the PCV valve hose from the intake
manifold nipple (Fig. 83). Cap the PCV vacuum nip-
ple.
(3) Disconnect purge hose from the nipple on the
throttle body (Fig. 84).
(4) Use a piece of hose to attach Air Metering Ori-
fice 6457 (0.125 in. orifice) to the purge nipple on the
throttle body (Fig. 85).
(5) Ensure that all accessories are off.
Fig. 82 MAP Sensor Connector
Fig. 83 PCV Vacuum Nipple
14 - 48 FUEL SYSTEMPL
DIAGNOSIS AND TESTING (Continued)

(6) Connect the DRB scan tool to the data link
connector inside the passenger compartment.
(7) Run engine in Park or Neutral until the cooling
fan has cycled on and off at least once (180ÉF).
(8) Using the DRB scan tool, access Minimum Air-
flow Idle Speed.
(9) The following will then occur:
²Idle air control motor will fully close
²Idle spark advance will become fixed
²PCM will go open loop enriched
²DRB scan tool displays engine RPM
(10) If idle RPM is within the range shown in the
Idle Specification chart, throttle body minimum air-
flow is set correctly.
IDLE SPECIFICATION Ð2.0L ENGINEOdometer Reading Idle RPM
Below 1000 Miles.................550±1300 RPM
Above 1000 Miles.................600±1300 Miles
(11) If idle RPM is above specifications, use the
DRB scan tool to check idle air control motor opera-
tion. If idle air control motor is OK, replace throttle
body. If idle air flow is below specification, shut off
the engine and clean the throttle body as follows:
WARNING: CLEAN THROTTLE BODY IN A WELL
VENTILATED AREA. WEAR RUBBER OR BUTYL
GLOVES, DO NOT LET MOPAR PARTS CLEANER
COME IN CONTACT WITH EYES OR SKIN. AVOID
INGESTING THE CLEANER. WASH THOROUGHLY
AFTER USING CLEANER.
(a) Remove the throttle body from engine.
(b) While holding the throttle open, spray the
entire throttle body bore and the manifold side of
the throttle plate with Mopar Parts Cleaner.Only
use Mopar Parts Cleaner to clean the throttle
body.
(c) Using a soft scuff pad, clean the top and bot-
tom of throttle body bore and the edges and mani-
fold side of the throttle blade.The edges of the
throttle blade and portions of the throttle
bore that are closest to the throttle blade
when closed, must be free of deposits.
(d) Use compressed air to dry the throttle body.
(e) Inspect throttle body for foreign material.
(f) Install throttle body on manifold.
(g) Repeat steps 1 through 14. If the minimum
air flow is still not within specifications, the prob-
lem is not caused by the throttle body.
(12) Shut off engine.
(13) Remove Air Metering Orifice 6457. Install
purge hose.
(14) Remove cap from PCV valve. Connect hose to
PCV valve.
(15) Remove DRB scan tool.
VEHICLE SPEED SENSOR
To perform a complete test of the sensor and its
circuitry, refer to the DRB scan tool and appropriate
Powertrain Diagnostics Procedures Manual.
Fig. 84 Purge Hose
Fig. 85 Orifice 6457 Attached to Purge Nipple
PLFUEL SYSTEM 14 - 49
DIAGNOSIS AND TESTING (Continued)

PUSHING connector off the lever nail head (Fig. 88)
and (Fig. 90). DO NOT try to pull connector off per-
pendicular to the lever.
(6) Compress the retaining tabs on the cable and
slide cable out of bracket (Fig. 89).
(7) if equipped with speed control, hold throttle
lever in the wide open position. Using finger pressure
only, remove speed control cable by PUSHING con-
nector off the lever nail head (Fig. 88) and (Fig. 91).
DO NOT try to pull connector off perpendicular to
the lever.
(8) Compress the retaining tabs on the cable and
slide cable out of bracket (Fig. 89).
(9) Remove 2 screws holding cable mounting
bracket and support bracket.
(10) Remove TPS connector.
(11) Remove Idle Air Control motor connector.
(12) Remove EVAP purge hose.
(13) Remove throttle body mounting bolts. Remove
throttle body.(14) The rubber O-ring gasket on the intake man-
ifold is reusable. Wipe the O-ring clean before install-
ing throttle body (Fig. 92).
INSTALLATION
(1) Connect electrical connection to throttle body.
(2) Install throttle body on intake manifold.
Tighten mounting bolts 11.8 N.m (105 in. lbs.).
(3) Attach cable mounting bracket and support
bracket with 2 screws.
(4) Connect the EVAP purge hose.
(5) Install cable housing(s) retainer tabs into
bracket.
(6) Install throttle body cables using the following
procedures.
(7) From the engine compartment, rotate the
throttle lever forward to the wide open position and
install throttle cable clasp (Fig. 89).
(8) If equipped with speed control, rotate throttle
lever forward to the wide open position and slide
speed control cable connector onto nail head.
Fig. 89 Disconnecting Throttle Cable
Fig. 90 Transmission Kickdown Cable Connector
Fig. 91 Speed Control Cable Connector
Fig. 92 Re-Usable Throttle Body Gasket
PLFUEL SYSTEM 14 - 51
REMOVAL AND INSTALLATION (Continued)