1995 JEEP YJ Service And Repair Manual

pairing phone jack points key fob reset clock reset octane

Page 1417 of 2158

JEEP YJ 1995 Service And Repair Manual (1) Disconnect negative battery cable.
(2) Remove the fuel filler cap. Using an approved
portable gasoline siphon/storage tank, drain fuel
tank.
(3) Raise and support vehicle.
(4) Using a small straig

Page 1418 of 2158

JEEP YJ 1995 Service And Repair Manual (2) Raise skid plate/fuel tank until gauge sender
wire connector can be connected to harness connec-
tor.
(3) Finish raising skid plate/fuel tank assembly
into position. Tighten mounting nuts to 16 Nz

(2) Raise skid plate/fuel tank until gauge sender
wire connector can be connected to harness connec-
tor.
(3) Finish raising skid plate/fuel tank assembly
into position. Tighten mounting nuts to 16 Nzm (12
ft. lbs.) torque. Remove transmission jack.
(4) Connect fuel fill hose and fill vent hose to filler
neck. Tighten hose clamps.
(5) Connect vent hose to vent tube.
(6) Connect fuel supply hose to the supply tube
and fuel return hose to return tube. Tighten hose
clamps.
(7) Install fuel filler neck shroud with push clips.
(8) Lower vehicle.
(9) Fill fuel tank. Install filler cap.
(10) Connect negative battery cable to battery.
(11) Start vehicle and inspect for leaks.
FUEL GAUGE SENDING UNIT
The fuel gauge sending unit is attached to the fuel
pump module. Refer to Fuel Pump Module in the
Fuel Delivery System section of this group.
FUEL TANK PRESSURE RELIEF/ROLLOVER VALVE
The fuel tank is equipped with a pressure relief/
rollover valve (Fig. 8). The dual function valve will
relieve fuel tank pressure and prevent fuel flow
through the fuel tank vent tubes in the event of ac-
cidental vehicle rollover.
The valve consists of a plunger, spring and orifice/
guide plate (Fig. 9). The valve is normally open al-
lowing fuel vapor to vent to the EVAP canister. Here
it is stored until it can be consumed by the engine
(under controlled conditions). The plunger seats inthe guide plate at the orifice preventing liquid fuel
from reaching the EVAP canister. This is done if bot-
tom of plunger is contacted by fuel sloshing in tank
when vehicle is cornering.
In the event of accidental vehicle rollover, the valve
is inverted. In this position the plunger is forced
against the guide plate and raw fuel is prevented
from flowing through the valve orifice into the fuel
tank vent tube.
REMOVAL
WARNING: THE FUEL SYSTEM IS UNDER A CON-
STANT PRESSURE (EVEN WITH THE ENGINE OFF).
BEFORE SERVICING THE PRESSURE RELIEF/
ROLLOVER VALVE, THE FUEL SYSTEM PRESSURE
MUST BE RELEASED. REFER TO THE FUEL PRES-
SURE RELEASE PROCEDURE IN THIS GROUP.
(1) Disconnect negative battery cable.
(2) Remove the fuel filler cap and drain fuel tank.
Refer to Fuel Tank Removal.
(3) Remove fuel tank. Refer to Fuel Tank Removal.
(4) The rollover valve is seated in a grommet. Re-
move by prying one side upward and then roll the
grommet out of tank (Fig. 8).
INSTALLATION
(1) Start one side of grommet into opening in fuel
tank. Using finger pressure only, press valve/grom-
met into place.
(2) Install fuel tank. Refer to Fuel Tank Installa-
tion.
(3) Fill fuel tank. Install fuel tank filler cap.
(4) Connect negative battery cable.
(5) Start vehicle and check for leaks.
Fig. 8 Valve LocationÐTypical
Fig. 9 Pressure Relief/Rollover Valve Operation
14 - 16 FUEL TANKSJ

Page 1419 of 2158

JEEP YJ 1995 Service And Repair Manual ACCELERATOR PEDAL AND THROTTLE CABLE
GENERAL INFORMATION
The accelerator pedal is connected to the throttle body
linkage by the throttle cable. The cable is protected by a
plastic sheathing and is con

ACCELERATOR PEDAL AND THROTTLE CABLE
GENERAL INFORMATION
The accelerator pedal is connected to the throttle body
linkage by the throttle cable. The cable is protected by a
plastic sheathing and is connected to the throttle body
linkage by a ball socket. It is connected to the upper part
of the accelerator pedal arm by a plastic retainer (clip)
(Fig. 10). This retainer (clip) snaps into the top of the ac-
celerator pedal arm. Retainer tabs (built into the cable
sheathing) (Fig. 10) fasten the cable to the dash panel.
Dual throttle return springs (attached to the throt-
tle shaft) are used to close the throttle.
CAUTION: Never attempt to remove or alter these
springs.
ACCELERATOR PEDAL
CAUTION: Be careful not to damage or kink the ca-
ble core wire (within the cable sheathing) while ser-
vicing the accelerator pedal or throttle cable.
REMOVAL
(1) From inside the vehicle, hold up accelerator
pedal. Remove plastic cable retainer (clip) and throt-
tle cable core wire from upper end of accelerator
pedal arm (Fig. 10). Plastic cable retainer (clip) snaps
into pedal arm.
(2) Remove accelerator pedal mounting bracket
nuts. Remove accelerator pedal assembly.
INSTALLATION
(1) Place accelerator pedal assembly over studs
protruding from floor pan. Tighten mounting nuts to
5Nzm (36 in. lbs.) torque.
(2) Slide throttle cable into opening in top of pedal
arm. Push plastic cable retainer (clip) into accelera-
tor pedal arm opening until it snaps into place.
(3) Before starting engine, operate accelerator
pedal to check for any binding.
THROTTLE CABLE
REMOVAL
(1) From inside the vehicle, hold up accelerator
pedal. Remove plastic cable retainer (clip) and throt-
tle cable core wire from upper end of accelerator
pedal arm (Fig. 10). Plastic cable retainer (clip) snaps
into pedal arm.
(2) Remove the cable core wire at pedal arm.
(3) From inside the vehicle, pinch both sides of the
cable housing retainer tabs (Fig. 10) at the dash
panel. Remove cable housing from dash panel and
pull into the engine compartment.
(4) Remove cable from clip on the engine cylinder
head (valve) cover.
(5) Remove the throttle cable ball end socket at
throttle body linkage (snaps off) (Fig. 11).
(6) Remove throttle cable from throttle body
mounting bracket by compressing retainer tabs and
pushing cable through hole in bracket. Remove throt-
tle cable from vehicle.
INSTALLATION
(1) Slide throttle cable through hole in throttle
body bracket until retainer tabs lock into bracket.
Connect cable ball end to throttle body linkage ball
(snaps on).
Fig. 10 Accelerator Pedal MountingÐTypical
Fig. 11 Throttle (Accelerator) CableÐTypical
JACCELERATOR PEDAL AND THROTTLE CABLE 14 - 17

Page 1420 of 2158

JEEP YJ 1995 Service And Repair Manual (2) Snap cable into clip on the engine cylinder
head (valve) cover.
(3) Push other end of cable through opening in
dash panel until retaining tabs lock into panel.
(4) From inside drivers compartment,

Page 1421 of 2158

JEEP YJ 1995 Service And Repair Manual MULTI-PORT FUEL INJECTION (MFI)ÐCOMPONENT DESCRIPTION/SYSTEM
OPERATION
INDEX
page page
Air Cleaner.............................. 29
Air Conditioning (A/C) Clutch RelayÐPCM Output . 26
Air Conditioni

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

Page 1422 of 2158

JEEP YJ 1995 Service And Repair Manual 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 th

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

Page 1423 of 2158

JEEP YJ 1995 Service And Repair Manual 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

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

Page 1424 of 2158

JEEP YJ 1995 Service And Repair Manual energized). This is done to compensate for the re-
duced flow through injector caused by the lowered
voltage.
BRAKE SWITCHÐPCM INPUT
When the brake light switch is activated, the pow-
ertrain control

energized). This is done to compensate for the re-
duced flow through injector caused by the lowered
voltage.
BRAKE SWITCHÐPCM INPUT
When the brake light switch is activated, the pow-
ertrain control module (PCM) receives an input indi-
cating that the brakes are being applied. After
receiving this input, the PCM maintains idle speed to
a scheduled rpm through control of the idle air con-
trol (IAC) motor. The brake switch input is also used
to operate the speed control system.
CAMSHAFT POSITION SENSORÐPCM INPUT
A sync signal is provided by the camshaft position
sensor located in the distributor (Fig. 5). The sync
signal from this sensor works in conjunction with the
crankshaft position sensor to provide the powertrain
control module (PCM) with inputs. This is done to es-
tablish and maintain correct injector firing order.
Refer to Camshaft Position Sensor in Group 8D, Ig-
nition System for more information.
DATA LINK CONNECTORÐPCM INPUT
The data link connector (diagnostic scan tool con-
nector) links the DRB scan tool with the powertrain
control module (PCM). The data link connector is lo-
cated in the engine compartment (Figs. 6 or 7). For
operation of the DRB scan tool, refer to the appropri-
ate Powertrain Diagnostic Procedures service man-
ual.
The data link connector uses two different pins on
the PCM. One is for Data Link Transmit and the
other is for Data Link Receive.
INTAKE MANIFOLD AIR TEMPERATURE SENSORÐ
PCM INPUT
The intake manifold air temperature sensor is in-
stalled in the intake manifold with the sensor ele-
ment extending into the air stream (Figs. 8 or 9). Thesensor provides an input voltage to the powertrain
control module (PCM) indicating intake manifold air
temperature. The input is used along with inputs
from other sensors to determine injector pulse width.
As the temperature of the air-fuel stream in the
manifold varies, the sensor resistance changes. This
results in a different input voltage to the PCM.
CRANKSHAFT POSITION SENSORÐPCM INPUT
This sensor is a Hall Effect device that detects
notches in the flywheel (manual transmission), or
flexplate (automatic transmission).
This sensor is used to indicate to the powertrain
control module (PCM) that a spark and or fuel injec-
tion event is to be required. The output from this
sensor, in conjunction with the camshaft position sen-
sor signal, is used to differentiate between fuel injec-
tion and spark events. It is also used to synchronize
the fuel injectors with their respective cylinders.
Refer to Group 8D, Ignition System for more crank-
shaft position sensor information.
Fig. 5 Camshaft Position Sensor
Fig. 6 Data Link ConnectorÐYJ ModelsÐTypical
Fig. 7 Data Link ConnectorÐXJ ModelsÐTypical
14 - 22 FUEL SYSTEM COMPONENT DESCRIPTION/SYSTEM OPERATIONJ

Load next 8 pages

Page: < prev 1-10 ... 1385-1392 1393-1400 1401-1408 1409-1416 1417-1424 1425-1432 1433-1440 1441-1448 1449-1456 ... 2160 next >

overheating brake pads set clock brake sensor jacking points jacking