1995 JEEP YJ oil temperature

The frame is constructed of high-strength channel
steel siderails and crossmembers. The crossmembers
join the siderails and retain them in alignment in re-
lation to each other. This provides resistance to
frame twists and strains.
FRAME STRAIGHTENING
When necessary, a conventional frame that is bent
or twisted can be straightened by application of heat.
The temperature must not exceed 566ÉC (1050ÉF).
The use of a specially designed heat crayon can de-
termine the desired temperature. Excessive heat will
decrease the strength of the metal and result in a
weakened frame.
Welding the joints around riveted cross members
and frame side rails is not recommended.
A straightening repair process should be limited to
frame members that are not severely damaged.
FRAME REPAIRS
DRILLING HOLES
Do not drill holes in frame side rail top and bottom
flanges, metal fatigue can result causing frame fail-
ure. Holes drilled in the side of the frame rail must
be at least 38 mm (1.5 in.) from the top and bottom
flanges.
Additional drill holes should be located away from
existing holes.
WELDING
Use MIG, TIG or arc welding equipment to repair
welded frame components.
Frame components that have been damaged should
be inspected for cracks before returning the vehicle
to use. If cracks are found in accessible frame com-
ponents perform the following procedures.
(1) Drill a hole at each end of the crack with a 3
mm (O.125 in.) diameter drill bit.
(2) Using a suitable die grinder with 3 inch cut off
wheel, V-groove the crack to allow 100% weld pene-
tration.
(3) Weld the crack.
(4) If necessary when a side rail is repaired, grind
the weld smooth and install a reinforcement channel
(Fig. 4) over the repaired area.
If a reinforcement channel is required, the
top and bottom flanges should be 0.250 inches
narrower than the side rail flanges. Weld only
in the areas indicated (Fig. 4).
FRAME FASTENERS
Bolts, nuts and rivets can be used to repair frames
or to install a reinforcement section on the frame.
Bolts can be used in place of rivets. When replacing
rivets with bolts, install the next larger size diameter
bolt to assure proper fit. If necessary, drill the hole
out just enough to receive the bolt.Conical-type washers are preferred over the split-
ring type lock washers. Normally, grade-5 bolts are
adequate for frame repair.Grade-3 bolts or softer
should not be used.Tightening bolts/nuts with the
correct torque, refer to the Introduction Group at the
front of this manual for tightening information.
FRAME DIMENSIONS
Frame dimensions are listed in millimeter scale.
All dimensions are from center to center of Principal
Locating Point (PLP), or from center to center of PLP
and fastener location (Fig. 5).
TOW HOOKS
REMOVAL
(1) Remove the two bolts that attach the tow hook
to the bumper rail and to the frame rail.
(2) Remove the tow hook.
INSTALLATION
(1) Position the tow hook on the bumper rail and
frame rail.
(2) Install the attaching bolts. Tighten the bolts to
102 Nzm (75 ft. lbs.) torque.
GENERATOR SPLASH SHIELD
REMOVAL
(1) Remove the shield retaining nut and washer
(Fig. 6) from the engine oil pan stud (2.5L engines
only).
(2) Pry the serrated retainers from the frame rail
holes at each side of the vehicle.
(3) Pry the serrated retainers from the fan shroud
holes (Fig. 6).
(4) Remove the shield from the vehicle.
Fig. 4 Frame Reinforcement
JYJÐFRAME 13 - 13

MULTI-PORT FUEL INJECTION (MFI)ÐCOMPONENT DESCRIPTION/SYSTEM
OPERATION
INDEX
page page
Air Cleaner.............................. 29
Air Conditioning (A/C) Clutch RelayÐPCM Output . 26
Air Conditioning (A/C) ControlsÐPCM Input...... 21
Auto Shutdown (ASD) RelayÐPCM Output...... 26
Automatic Shutdown (ASD) SenseÐPCM Input . . . 21
Battery VoltageÐPCM Input................. 21
Brake SwitchÐPCM Input................... 22
Camshaft Position SensorÐPCM Input......... 22
Crankshaft Position SensorÐPCM Input........ 22
Data Link ConnectorÐPCM Input............. 22
Data Link ConnectorÐPCM Output............ 27
EMR LampÐPCM Output................... 27
Engine Coolant Temperature SensorÐPCM Input . 23
Extended Idle SwitchÐPCM Input............. 23
Fuel InjectorsÐPCM Output................. 27
Fuel Pressure Regulator.................... 33
Fuel Pump RelayÐPCM Output.............. 27
Fuel Rail................................ 33
General Information....................... 19
Generator FieldÐPCM Output................ 27
Generator LampÐPCM Output............... 27
Idle Air Control (IAC) MotorÐPCM Output....... 27
Ignition Circuit SenseÐPCM Input............. 23
Ignition CoilÐPCM Output................... 28Intake Manifold Air Temperature SensorÐ
PCM Input............................. 22
Malfunction Indicator LampÐPCM Output....... 28
Manifold Absolute Pressure (MAP) SensorÐPCM
Input................................. 23
Open Loop/Closed Loop Modes of Operation..... 30
Oxygen (O2S) SensorÐPCM Input............ 24
Park/Neutral SwitchÐPCM Input.............. 24
Power Ground........................... 24
Power Steering Pressure SwitchÐPCM Input.... 24
Powertrain Control Module (PCM)............. 20
Radiator Fan RelayÐPCM Output............. 28
SCI ReceiveÐPCM Input................... 24
SCI TransmitÐPCM Output.................. 29
Sensor ReturnÐPCM Input.................. 25
Shift IndicatorÐPCM Output................. 29
Speed ControlÐPCM Input.................. 25
Speed ControlÐPCM Output................. 29
TachometerÐPCM Output................... 29
Throttle Body............................ 33
Throttle Position Sensor (TPS)ÐPCM Input...... 25
Torque Converter Clutch RelayÐPCM Output.... 29
Vehicle Speed SensorÐPCM Input............ 25
GENERAL INFORMATION
All 2.5L 4-cylinder and 4.0L 6-cylinder engines are
equipped with sequential Multi-Port Fuel Injection
(MFI). The MFI system provides precise air/fuel ra-
tios for all driving conditions.
The Powertrain Control Module (PCM) operates
the fuel system. The PCM was formerly referred to
as the SBEC or engine controller. The PCM is a pre-
programmed, dual microprocessor digital computer. It
regulates ignition timing, air-fuel ratio, emission con-
trol devices, charging system, speed control, air con-
ditioning compressor clutch engagement and idle
speed. The PCM can adapt its programming to meet
changing operating conditions.
Powertrain Control Module (PCM) Inputsrep-
resent the instantaneous engine operating conditions.
Air-fuel mixture and ignition timing calibrations for
various driving and atmospheric conditions are pre-
programmed into the PCM. The PCM monitors and
analyzes various inputs. It then computes engine fuel
and ignition timing requirements based on these in-
puts. Fuel delivery control and ignition timing will
then be adjusted accordingly.
Other inputs to the PCM are provided by the brake
light switch, air conditioning select switch and the
speed control switches. All inputs to the PCM are
converted into signals.
Electrically operated fuel injectors spray fuel inprecise metered amounts into the intake port directly
above the intake valve. The injectors are fired in a
specific sequence by the PCM. The PCM maintains
an air/fuel ratio of 14.7 to 1 by constantly adjusting
injector pulse width. Injector pulse width is the
length of time that the injector opens and sprays fuel
into the chamber. The PCM adjusts injector pulse
width by opening and closing the ground path to the
injector.
Manifold absolute pressure (air density) and engine
rpm (speed) are the primary inputs that determine
fuel injector pulse width. The PCM also monitors
other inputs when adjusting air-fuel ratio.
Inputs That Effect Fuel Injector Pulse Width:
²Exhaust gas oxygen content
²Engine coolant temperature
²Manifold absolute pressure (MAP)
²Engine speed
²Throttle position
²Battery voltage
²Air conditioning selection
²Transmission gear selection (automatic transmis-
sions only)
²Speed control
The powertrain control module (PCM) adjusts igni-
tion timing by controlling ignition coil operation. The
ignition coil receives battery voltage when the igni-
tion key is in the run or starter position. The PCM
JFUEL SYSTEM COMPONENT DESCRIPTION/SYSTEM OPERATION 14 - 19

provides a ground for the ignition coil. The coil dis-
charges when the PCM supplies a ground. By switch-
ing the ground path on and off, the PCM regulates
ignition timing.
The sensors and switches that provide inputs to
the powertrain control module (PCM) comprise the
Engine Control System. It is also comprised of the
PCM Outputs (engine control devices that the are op-
erated by the PCM).
SYSTEM DIAGNOSIS
The powertrain control module (PCM) tests many
of its own input and output circuits. If a Diagnostic
Trouble Code (DTC) is found in a major system, this
information is stored in the PCM memory. Refer to
On-Board Diagnostics in the MFI SystemÐGeneral
Diagnosis section of this group for DTC information.
POWERTRAIN CONTROL MODULE (PCM)
The PCM operates the fuel system. The PCM was
formerly referred to as the SBEC or engine control-
ler. The PCM is a pre-programmed, dual microproces-
sor digital computer. It regulates ignition timing, air-
fuel ratio, emission control devices, charging system,
speed control, air conditioning compressor clutch en-
gagement and idle speed. The PCM can adapt its
programming to meet changing operating conditions.
On XJ models, the PCM is located in the engine
compartment next to the air cleaner (Fig. 1). On YJ
models, the PCM is located in the engine compart-
ment behind the windshield washer fluid reservoir
(Fig. 2).
The PCM receives input signals from various
switches and sensors. Based on these inputs, the
PCM regulates various engine and vehicle operations
through different system components. These compo-
nents are referred to as PCM Outputs. The sensors
and switches that provide inputs to the PCM are con-
sidered PCM Inputs.The PCM adjusts ignition timing based upon in-
puts it receives from sensors that react to: engine
rpm, manifold absolute pressure, coolant tempera-
ture, throttle position, transmission gear selection
(automatic transmission), vehicle speed and the
brake switch.
The PCM adjusts idle speed based on inputs it re-
ceives from sensors that react to: throttle position,
vehicle speed, transmission gear selection, coolant
temperature and from inputs it receives from the air
conditioning clutch switch and brake switch.
Based on inputs that it receives, the PCM adjusts
ignition coil dwell. The PCM also adjusts the gener-
ator charge rate through control of the generator
field and provides speed control operation.
Powertrain Control Module (PCM) Inputs:
²Generator output
²A/C request (if equipped with factory A/C)
²A/C select (if equipped with factory A/C)
²Auto shutdown (ASD) sense
²Intake manifold air temperature sensor
²Battery voltage
²Brake switch
²Engine coolant temperature sensor
²Crankshaft position sensor
²Ignition circuit sense (ignition switch in run posi-
tion)
²Manifold absolute pressure sensor
²Overdrive/override switch
²Oxygen sensor
²Park/neutral switch (auto. trans. only)
²SCI receive (DRB scan tool connection)
²Speed control resume switch
²Speed control set switch
²Speed control on/off switch
²Camshaft position sensor signal
²Throttle position sensor
²Vehicle speed sensor
²Sensor return
²Power ground
Fig. 1 PCM LocationÐXJ Models
Fig. 2 PCM LocationÐYJ Models
14 - 20 FUEL SYSTEM COMPONENT DESCRIPTION/SYSTEM OPERATIONJ

²Signal ground
Powertrain Control Module (PCM) Outputs:
²A/C clutch relay
²Idle air control (IAC) motor
²Auto shutdown (ASD) relay
²Generator field
²Malfunction indicator lamp (Check Engine Lamp)
²Fuel injectors
²Fuel pump relay
²Ignition coil
²SCI transmit (DRB scan tool connection)
²Shift indicator lamp (manual transmission only)
²Speed control vacuum solenoid
²Speed control vent solenoid
²Tachometer (on instrument panel, if equipped)
²Torque converter clutch relay (3-speed auto. trans.
only)
The PCM contains a voltage convertor. This con-
verts battery voltage to a regulated 8.0 volts. It is
used to power the crankshaft position sensor, cam-
shaft position sensor and vehicle speed sensor. The
PCM also provides a five (5) volt supply for the Man-
ifold Absolute Pressure (MAP) sensor and Throttle
Position Sensor (TPS).
AIR CONDITIONING (A/C) CONTROLSÐPCM INPUT
The A/C control system information applies to fac-
tory installed air conditioning units only.
A/C SELECT SIGNAL:When the A/C switch is in
the ON position and the A/C low-pressure switch is
closed, an input signal is sent to the powertrain con-
trol module (PCM). The signal informs the PCM that
the A/C has been selected. The PCM adjusts idle
speed to a pre-programmed rpm through the idle air
control (IAC) motor to compensate for increased en-
gine load.
A/C REQUEST SIGNAL:Once A/C has been se-
lected, the PCM receives the A/C request signal from
the evaporator switch. The input indicates that the
evaporator temperature is in the proper range for
A/C application. The PCM uses this input to cycle the
A/C compressor clutch (through the A/C relay). It will
also determine the correct engine idle speed through
the IAC motor position.
If the A/C low-pressure switch opens (indicating a
low refrigerant level), the PCM will not receive an
A/C select signal. The PCM will then remove the
ground from the A/C relay. This will deactivate the
A/C compressor clutch.
If the evaporator switch opens, (indicating that
evaporator is not in proper temperature range), the
PCM will not receive the A/C request signal. The
PCM will then remove the ground from the A/C relay,
deactivating the A/C compressor clutch.
AUTOMATIC SHUTDOWN (ASD) SENSEÐPCM
INPUT
A 12 volt signal at this input indicates to the PCM
that the ASD has been activated. The ASD relay is
located in the power distribution center (PDC) in the
engine compartment (Figs. 3 or 4). It is used to con-
nect the ignition coil, generator field winding and
fuel injectors to 12 volt + power supply. Also refer to
Automatic Shutdown RelayÐPCM Output.
This input is used only to sense that the ASD relay
is energized. If the PCM does not see 12 volts at this
input when the ASD should be activated, it will set a
Diagnostic Trouble Code (DTC).
BATTERY VOLTAGEÐPCM INPUT
The battery voltage input provides power to the
powertrain control module (PCM). It also informs the
PCM what voltage level is supplied to the ignition
coil and fuel injectors.
If battery voltage is low, the PCM will increase in-
jector pulse width (period of time that the injector is
Fig. 3 Power Distribution CenterÐYJ Models
Fig. 4 Power Distribution CenterÐXJ Models
JFUEL SYSTEM COMPONENT DESCRIPTION/SYSTEM OPERATION 14 - 21

The MAP sensor is mounted on the dash panel.
The sensor is connected to the throttle body with a
vacuum hose and to the PCM electrically.
OXYGEN (O2S) SENSORÐPCM INPUT
The O2S sensor is located in the exhaust down pipe
(Fig. 11). It provides an input voltage to the power-
train control module (PCM) relating the oxygen con-
tent of the exhaust gas. The PCM uses this
information to fine tune the air-fuel ratio by adjust-
ing injector pulse width.
The O2S sensor produces voltages from 0 to 1 volt.
This voltage will depend upon the oxygen content of
the exhaust gas in the exhaust manifold. When a
large amount of oxygen is present (caused by a lean
air-fuel mixture), the sensor produces a low voltage.
When there is a lesser amount present (rich air-fuel
mixture) it produces a higher voltage. By monitoring
the oxygen content and converting it to electrical
voltage, the sensor acts as a rich-lean switch.
The oxygen sensor is equipped with a heating ele-
ment that keeps the sensor at proper operating tem-
perature during all operating modes. Maintaining
correct sensor temperature at all times allows the
system to enter into closed loop operation sooner.
In Closed Loop operation, the powertrain control
module (PCM) monitors the O2S sensor input (along
with other inputs). It then adjusts the injector pulse
width accordingly. During Open Loop operation, the
PCM ignores the O2S sensor input and adjusts injec-
tor pulse width to a preprogrammed value (based on
other sensor inputs).
PARK/NEUTRAL SWITCHÐPCM INPUT
The park/neutral switch is located on the transmis-
sion housing and provides an input to the powertrain
control module (PCM). This will indicate that the au-
tomatic transmission is in Park, Neutral or a drive
gear selection. This input is used to determine idle
speed (varying with gear selection), fuel injector
pulse width, ignition timing advance and vehiclespeed control operation. Refer to Group 21, Transmis-
sions, for testing, replacement and adjustment infor-
mation.
POWER GROUND
The power ground is used to control ground circuits
for the following powertrain control module (PCM)
loads:
²Generator Field Winding
²8 volt (PCM) power supply
²Fuel Injectors
²Ignition Coil
POWER STEERING PRESSURE SWITCHÐPCM
INPUT
A pressure sensing switch is included in the power
steering system (mounted on the high-pressure line).
This switch will be on vehicles equipped with a 2.5L
engine and power steering. The switch (figure 12, YJ
models or figure 13, XJ models) provides an input to
the PCM. This input is provided during periods of
high pump load and low engine rpm; such as during
parking maneuvers. The PCM will then increase the
idle speed through the idle air control (IAC) motor.
This is done to prevent the engine from stalling un-
der the increased load.
When steering pump pressure exceeds 1896 kPa6
172 kPa (275625 psi) the PCM will increase the en-
gine idle speed. This will prevent the engine from
stalling.
SCI RECEIVEÐPCM INPUT
SCI Receive is the serial data communication re-
ceive circuit for the DRB scan tool. The powertrain
control module (PCM) receives data from the DRB
through the SCI Receive circuit.
Fig. 11 Heated Oxygen Sensor LocationÐTypicalFig. 12 Power Steering Pump Pressure SwitchÐYJ
Models
14 - 24 FUEL SYSTEM COMPONENT DESCRIPTION/SYSTEM OPERATIONJ

The throttle body has an air control passage that
provides air for the engine at idle (the throttle plate
is closed). The IAC motor pintle protrudes into the
air control passage and regulates air flow through it.
Based on various sensor inputs, the powertrain con-
trol module (PCM) adjusts engine idle speed by mov-
ing the IAC motor pintle in and out of the air control
passage. The IAC motor is positioned when the igni-
tion key is turned to the On position.
A (factory adjusted) set screw is used to mechani-
cally limit the position of the throttle body throttle
plate.Never attempt to adjust the engine idle
speed using this screw.All idle speed functions are
controlled by the PCM.
IGNITION COILÐPCM OUTPUT
System voltage is supplied to the ignition coil pos-
itive terminal. The powertrain control module (PCM)
operates the ignition coil.Base (initial) ignition
timing is not adjustable.The PCM adjusts ignition
timing to meet changing engine operating conditions.
The ignition coil is located near the distributor
(Fig. 22).
Refer to Group 8D, Ignition System for additional
information.
MALFUNCTION INDICATOR LAMPÐPCM OUTPUT
The malfunction indicator lamp illuminates each
time the ignition key is turned on. It will stay on for
approximately three seconds as a bulb test. The lamp
is displayed on the instrument panel as the CHECK
ENGINE lamp (Figs. 23 or 24).
If the powertrain control module (PCM) receives an
incorrect signal, or no signal from certain sensors or
emission related systems, the lamp is turned on. This
is a warning that the PCM has recorded a system or
sensor malfunction. In some cases, when a problem is
declared, the PCM will go into a limp-in mode. This
is an attempt to keep the system operating. It signals
an immediate need for service.The lamp can also be used to display a Diagnostic
Trouble Code (DTC). Cycle the ignition switch On-
Off-On-Off-On within three seconds and any codes
stored in the PCM memory will be displayed. This is
done in a series of flashes representing digits. Refer
to On-Board Diagnostics in the General Diagnosis
section of this group for more information.
RADIATOR FAN RELAYÐPCM OUTPUT
XJ MODELS ONLY
The electric radiator cooling fan used in XJ models
(equipped with 4.0L engine, heavy duty cooling
and/or air conditioning) is controlled by the power-
train control module (PCM) through radiator fan re-
lay. The relay is energized when coolant temperature
is above 103ÉC (217ÉF). It will then de-energize when
Fig. 22 Ignition CoilÐTypical
Fig. 23 Check Engine LampÐXJ ModelsÐTypical
Fig. 24 Check Engine LampÐYJ ModelsÐTypical
14 - 28 FUEL SYSTEM COMPONENT DESCRIPTION/SYSTEM OPERATIONJ

²The PCM adjusts ignition timing by increasing
and decreasing spark advance.
²The PCM operates the A/C compressor clutch
through the clutch relay. This happens if A/C has
been selected by the vehicle operator and requested
by the A/C thermostat.
The optional Extended Idle Switch is used to raise
the engine idle speed to approximately 1000 rpm.
This is when the shifter is in either the Park or Neu-
tral position. A rocker-type 2-wire switch (extended
idle switch) is mounted to the instrument panel. This
switch will supply a ground circuit to the powertrain
control module (PCM).The switch is available
only with 4.0L engine when supplied with the
optional police package.
CRUISE MODE
When the engine is at operating temperature, this
is a Closed Loop mode. At cruising speed, the power-
train control module (PCM) receives inputs from:
²Air conditioning select signal (if equipped)
²Air conditioning request signal (if equipped)
²Battery voltage
²Engine coolant temperature sensor
²Crankshaft position sensor
²Intake manifold air temperature sensor
²Manifold absolute pressure (MAP) sensor
²Throttle position sensor (TPS)
²Camshaft position sensor signal (in the distribu-
tor)
²Park/neutral switch (gear indicator signalÐauto.
trans. only)
²Oxygen (O2S) sensor
Based on these inputs, the following occurs:
²Voltage is applied to the fuel injectors with the
PCM. The PCM will then adjust the injector pulse
width by turning the ground circuit to each individ-
ual injector on and off.
²The PCM monitors the O2S sensor input and ad-
justs air-fuel ratio. It also adjusts engine idle speed
through the idle air control (IAC) motor.
²The PCM adjusts ignition timing by turning the
ground path to the coil on and off.
²The PCM operates the A/C compressor clutch
through the clutch relay. This happens if A/C has
been selected by the vehicle operator and requested
by the A/C thermostat.
ACCELERATION MODE
This is an Open Loop mode. The powertrain control
module (PCM) recognizes an abrupt increase in
throttle position or MAP pressure as a demand for
increased engine output and vehicle acceleration. The
PCM increases injector pulse width in response to in-
creased throttle opening.
DECELERATION MODE
When the engine is at operating temperature, this
is an Open Loop mode. During hard deceleration, the
powertrain control module (PCM) receives the follow-
ing inputs.
²Air conditioning select signal (if equipped)
²Air conditioning request signal (if equipped)
²Battery voltage
²Engine coolant temperature sensor
²Crankshaft position sensor
²Intake manifold air temperature sensor
²Manifold absolute pressure (MAP) sensor
²Throttle position sensor (TPS)
²Camshaft position sensor signal (in the distribu-
tor)
²Park/neutral switch (gear indicator signalÐauto.
trans. only)
If the vehicle is under hard deceleration with the
proper rpm and closed throttle conditions, the PCM
will ignore the oxygen sensor input signal. The PCM
will enter a fuel cut-off strategy in which it will not
supply battery voltage to the injectors. If a hard de-
celeration does not exist, the PCM will determine the
proper injector pulse width and continue injection.
Based on the above inputs, the PCM will adjust en-
gine idle speed through the idle air control (IAC) mo-
tor.
The PCM adjusts ignition timing by turning the
ground path to the coil on and off.
The PCM opens the ground circuit to the A/C
clutch relay to disengage the A/C compressor clutch.
This is done until the vehicle is no longer under de-
celeration (if the A/C system is operating).
WIDE OPEN THROTTLE MODE
This is an Open Loop mode. During wide open
throttle operation, the powertrain control module
(PCM) receives the following inputs.
²Battery voltage
²Crankshaft position sensor
²Engine coolant temperature sensor
²Intake manifold air temperature sensor
²Manifold absolute pressure (MAP) sensor
²Throttle position sensor (TPS)
²Camshaft position sensor signal (in the distribu-
tor)
During wide open throttle conditions, the following
occurs:
²Voltage is applied to the fuel injectors with the
powertrain control module (PCM). The PCM will
then control the injection sequence and injector pulse
width by turning the ground circuit to each individ-
ual injector on and off. The PCM ignores the oxygen
sensor input signal and provides a predetermined
amount of additional fuel. This is done by adjusting
injector pulse width.
²The PCM adjusts ignition timing by turning the
ground path to the coil on and off.
14 - 32 FUEL SYSTEM COMPONENT DESCRIPTION/SYSTEM OPERATIONJ

MULTI-PORT FUEL INJECTION (MFI)ÐGENERAL DIAGNOSIS
INDEX
page page
Automatic Shutdown (ASD) Relay Testing....... 46
Camshaft Position Sensor Test............... 46
Crankshaft Position Sensor Test.............. 47
Diagnostic Trouble Code (DTC)............... 54
DRB Scan Tool........................... 54
Engine Coolant Temperature Sensor Test....... 46
Extended Idle Switch Test................... 48
Fuel Injector Test......................... 51
Fuel Pump Relay Testing................... 47
Fuel System Pressure Test.................. 51
General Information....................... 35
Idle Air Control Motor Test................... 49
Intake Manifold Air Temperature Sensor Test..... 46Manifold Absolute Pressure (Map) Sensor Test . . . 47
On-Board Diagnostics (OBD)................. 51
Oxygen Sensor (O2S) Heating Element Test..... 48
Pcm System Schematics.................... 41
Powertrain Control Module (PCM) 60-Way
Connector............................. 40
RelaysÐOperation/Testing.................. 50
Starter Motor Relay Test.................... 51
Throttle Position Sensor (TPS) Test............ 48
Torque Converter Clutch Relay Test............ 48
Vehicle Speed Sensor Test.................. 48
Visual Inspection.......................... 35
GENERAL INFORMATION
All 2.5L 4-cylinder and 4.0L 6-cylinder engines are
equipped with sequential Multi-Port Fuel Injection
(MFI). The MFI system provides precise air/fuel ra-
tios for all driving conditions.
VISUAL INSPECTION
A visual inspection for loose, disconnected, or incor-
rectly routed wires and hoses should be made. This
should be done before attempting to diagnose or ser-
vice the fuel injection system. A visual check will
help spot these faults and save unnecessary test and
diagnostic time. A thorough visual inspection will in-
clude the following checks:
(1) Verify that the 60-way connector is fully in-
serted into the connector of the powertrain control
module (PCM) (Figs. 1 or 2). Verify that the connec-
tor mounting bolt is tightened to 4 Nzm (35 in. lbs.)
torque.(2) Inspect the battery cable connections. Be sure
they are clean and tight.
(3) Inspect fuel pump relay and air conditioning
compressor clutch relay (if equipped). Inspect ASD
relay and radiator fan relay (if equipped) connec-
tions. Inspect starter motor relay connections. In-
spect relays for signs of physical damage and
corrosion. The relays are installed in the power dis-
tribution center (PDC) (Figs. 3 or 4).
(4) Inspect ignition coil connections. Verify that coil
secondary cable is firmly connected to coil (Figs. 5 or
6).
(5) Verify that distributor cap is correctly attached
to distributor. Be sure that spark plug cables are
firmly connected to the distributor cap and the spark
plugs in their correct firing order. Be sure that coil
cable is firmly connected to distributor cap and coil.
Be sure that camshaft position sensor wire connector
is firmly connected to harness connector (Figs. 7 or
8). Inspect spark plug condition. Refer to Group 8D,
Fig. 1 PCMÐYJ Models
Fig. 2 PCMÐXJ Models
JFUEL SYSTEM GENERAL DIAGNOSIS 14 - 35