oil temperature JEEP YJ 1995 Service And Workshop 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 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

(8) Disconnect jumper wires from relay and 12 Volt
power source.
If continuity or resistance tests did not pass, re-
place relay. If tests passed, refer to Group 8W, Wiring
Diagrams for additional circuit information. Also re-
fer to the appropriate Powertrain Diagnostic Proce-
dures manual for operation of the DRB scan tool.
STARTER MOTOR RELAY TEST
Refer to Group 8A, Battery/Starting/Charging/Sys-
tem Diagnostics, for starter motor relay testing.
FUEL INJECTOR TEST
To perform a complete test of the fuel injectors and
their circuitry, refer to DRB scan tool and appropri-
ate Powertrain Diagnostics Procedures manual. To
test the injector only, refer to the following:
Disconnect the injector wire connector from the in-
jector. Place an ohmmeter on the injector terminals.
Resistance reading should be approximately 14.5
ohms61.2 ohms at 20ÉC (68ÉF). Proceed to the fol-
lowing Injector Diagnosis chart.When performing
the following tests from the chart, do not leave
electrical current applied to the injector for
longer than five seconds. Damage to injector
coil or internal injector seals could result.
FUEL SYSTEM PRESSURE TEST
Refer to the Fuel Delivery System section of this
group. See Fuel System Pressure Test.
ON-BOARD DIAGNOSTICS (OBD)
The powertrain control module (PCM) has been
programmed to monitor many different circuits of the
fuel injection system. If a problem is sensed in a
monitored circuit often enough to indicate an actual
problem, a Diagnostic Trouble Code (DTC) is stored.
The DTC will be stored in the PCM memory for even-
tual display to the service technician. If the problem
is repaired or ceases to exist, the PCM cancels the
DTC after 51 engine starts.Certain criteria must be met for a diagnostic trou-
ble code (DTC) to be entered into PCM memory. The
criteria may be a specific range of engine rpm, engine
temperature and/or input voltage to the PCM.
It is possible that a DTC for a monitored circuit
may not be entered into memory even though a mal-
function has occurred. This may happen because one
of the DTC criteria for the circuit has not been met.
Example: assume that one of the criteria for the
MAP sensor circuit is that the engine must be oper-
ating between 750 and 2000 rpm to be monitored for
a DTC. If the MAP sensor output circuit shorts to
ground when the engine rpm is above 2400 rpm, a 0
volt input will be seen by the PCM. A DTC will not
be entered into memory because the condition does
not occur within the specified rpm range.
A DTC indicates that the powertrain control mod-
ule (PCM) has recognized an abnormal signal in a
circuit or the system. A DTC may indicate the result
of a failure, but never identify the failed component
directly.
There are several operating conditions that the
PCM does not monitor and set a DTC for. Refer to
the following Monitored Circuits and Non-Monitored
Circuits in this section.
MONITORED CIRCUITS
The powertrain control module (PCM) can detect
certain problems in the fuel injection system.
Open or Shorted Circuit- The PCM can deter-
mine if sensor output (which is the input to PCM) is
within proper range. It also determines if the circuit
is open or shorted.
Output Device Current Flow- The PCM senses
whether the output devices are hooked up.
If there is a problem with the circuit, the PCM
senses whether the circuit is open, shorted to ground
(-), or shorted to (+) voltage.
Oxygen Sensor- The PCM can determine if the
oxygen sensor is switching between rich and lean.
This is, once the system has entered Closed Loop. Re-
fer to Open Loop/Closed Loop Modes Of Operation in
the Component Description/System Operation section
for an explanation of Closed (or Open) Loop opera-
tion.
NON-MONITORED CIRCUITS
The PCM does not monitor the following circuits,
systems or conditions that could have malfunctions
that result in driveability problems. A Diagnostic
Trouble Code (DTC) may not be displayed for these
conditions.
Fuel Pressure:Fuel pressure is controlled by the
vacuum assisted fuel pressure regulator. The PCM
cannot detect a clogged fuel pump inlet filter, clogged
in-line fuel filter, or a pinched fuel supply or return
Fig. 44 Fuel Injector Internal ComponentsÐTypical
JFUEL SYSTEM GENERAL DIAGNOSIS 14 - 51

MULTI-PORT FUEL INJECTION (MFI)ÐCOMPONENT REMOVAL/INSTALLATION
INDEX
page page
Accelerator Pedal and Throttle Cable........... 58
Air Cleaner Element....................... 59
Air Cleaner Housing....................... 58
Air Conditioning (A/C) Clutch Relay............ 58
Automatic Shutdown (ASD) Relay............. 59
Brake Switch............................ 59
Camshaft Position Sensor................... 60
Crankshaft Position Sensor.................. 60
Engine Coolant Temperature Sensor........... 60
Fuel Filter............................... 60
Fuel Injector............................. 60
Fuel Pressure Regulator.................... 61
Fuel Pump Module........................ 61
Fuel Pump Relay......................... 61
Fuel Rail Assembly........................ 62
Fuel System Pressure Release Procedure....... 62
Fuel Tank Pressure Relief/Rollover Valve........ 62Fuel Tanks.............................. 62
Fuel Tubes/Lines/Hoses and Clamps........... 62
Idle Air Control (IAC) Motor.................. 62
Ignition Coil............................. 62
Intake Manifold........................... 63
Intake Manifold Air Temperature Sensor......... 60
Manifold Absolute Pressure (Map) Sensor....... 63
Oxygen (O2S) Sensor...................... 63
Park Neutral Switch....................... 63
Power Steering Pressure SwitchÐ2.5L
Engine Only............................ 63
Powertrain Control Module (PCM)............. 64
Quick-Connect Fittings..................... 64
Throttle Body............................ 64
Throttle Position Sensor (TPS)............... 65
Torque Converter Clutch Relay............... 65
Vehicle Speed Sensor...................... 66
ACCELERATOR PEDAL AND THROTTLE CABLE
Refer to the Accelerator Pedal and Throttle Cable
section of this group for removal/installation proce-
dures.
AIR CONDITIONING (A/C) CLUTCH RELAY
The A/C clutch relay is located in the power distri-
bution center (PDC) (Figs. 1 or 2). For location of this
relay within the PDC, refer to label on PDC cover.
AIR CLEANER HOUSING
REMOVAL
(1) Unlock clean air hose clamp (Figs. 3 or 4) at air
cleaner cover. To unlock the clamp, attach adjustablepliers to clamp and rotate pliers as shown in figure
5. Remove clean air hose at cover.
(2) Disconnect vacuum lines at air cleaner housing.
(3) YJ Models: Release the three over-center type
clamps securing the housing to the housing bracket.
XJ Models: Remove the housing cover and remove air
cleaner element. Remove two bolts and one nut.
(4) Release the air cleaner housing from the ambi-
ent air inlet and remove housing from vehicle.
INSTALLATION
(1) Position air cleaner housing to body and ambi-
ent air inlet.
(2) YJ Models: Lock the three over-center type
clamps securing the housing to the housing bracket.
XJ Models: Install two bolts and one nut to housing.
Install air cleaner element and cover.
(3) Install vacuum lines to housing.
Fig. 1 PDCÐYJ Models
Fig. 2 PDCÐXJ Models
14 - 58 FUEL SYSTEM COMPONENT REMOVAL/INSTALLATIONJ

30RH/32RH TRANSMISSION DIAGNOSIS
INDEX
page page
Air Pressure Test......................... 74
Analyzing the Road Test.................... 71
Converter Housing Leak Diagnosis............ 75
Converter Stall Test........................ 74
Diagnosis Guides and Charts................ 77
Effects of Incorrect Fluid Level............... 71
Fluid Level Check......................... 70Gearshift Cable/Linkage Adjustment........... 71
General Information....................... 70
Hydraulic Pressure Test.................... 72
Preliminary Diagnosis...................... 70
Road Test............................... 71
Transmission Throttle Valve Cable Adjustment.... 71
GENERAL INFORMATION
Automatic transmission problems are generally a
result of:
²poor engine performance
²incorrect fluid level
²incorrect throttle valve cable adjustment
²incorrect band adjustment
²incorrect hydraulic control pressure adjustments
²hydraulic component malfunctions
²mechanical component malfunctions.
Begin diagnosis by checking the easily accessible
items such as fluid level, fluid condition and control
linkage adjustment. A road test will determine if fur-
ther diagnosis is necessary.
Procedures outlined in this section should be per-
formed in the following sequence to realize the most
accurate results:
²Preliminary diagnosis
²Check fluid level and condition
²Check control linkage Adjustment
²Road test
²Stall test
²Hydraulic pressure test
²Air pressure tests
²Leak test
²Analyze test results and consult diagnosis charts
PRELIMINARY DIAGNOSIS
Two basic procedures are required. One procedure
for vehicles that are driveable and an alternate pro-
cedure for disabled vehicles (will not back up or move
forward).
Vehicle Is Driveable
(1) Check fluid level and condition.
(2) Adjust throttle cable and gearshift linkage if
complaint was based on delayed, erratic, or harsh
shifts.
(3) Road test vehicle and note transmission operat-
ing characteristics.(4) Perform stall test if complaint is based on slug-
gish, low speed acceleration or abnormal throttle
opening needed to maintain normal speeds with
properly tuned engine.
(5) Perform hydraulic pressure tests.
(6) Perform air pressure test to check clutch-band
operation.
Vehicle Is Disabled
(1) Check fluid level and condition.
(2) Check for broken, disconnected throttle linkage.
(3) Check for cracked, leaking cooler lines, or loose,
missing pressure port plugs.
(4) Raise vehicle, start engine, shift transmission
into gear and note following:
(a) If propeller shafts turn but wheels do not,
problem is with differential or axle shafts.
(b) If propeller shafts do not turn and transmis-
sion is noisy, stop engine. Remove oil pan, and
check for debris. If pan is clear, remove transmis-
sion and check for damaged drive plate, converter,
oil pump or input shaft.
(c) If propeller shafts do not turn and transmis-
sion is not noisy, perform hydraulic pressure test to
determine if problem is a hydraulic or mechanical.
FLUID LEVEL CHECK
Transmission fluid level should be checked monthly
under normal operation. If the vehicle is used for
trailer towing or similar heavy load hauling, check
fluid level and condition weekly.
Fluid level is checked with the engine running at
curb idle speed, the transmission in Neutral and the
transmission fluid at normal operating temperature.
FLUID LEVEL CHECK PROCEDURE
(1) Transmission fluid must be at normal operating
temperature for accurate fluid level check. Drive ve-
hicle if necessary to bring fluid temperature up to
normal hot operating temperature of 82ÉC (180ÉF).
(2) Position vehicle on level surface. This is ex-
tremely important for accurate fluid level check.
(3) Start and run engine at curb idle speed.
21 - 70 30RH/32RH TRANSMISSION DIAGNOSISJ

CONVERTER STALL TEST
Stall testing involves determining maximum engine
rpm obtainable at full throttle with the rear wheels
locked and the transmission in D range. This test
checks the holding ability of the converter overrun-
ning clutch and both of the transmission clutches.
When stall testing is completed, refer to the Stall
Speed Specifications chart and Stall Speed Diagnosis
guides.
WARNING: NEVER ALLOW ANYONE TO STAND IN
FRONT OF THE VEHICLE DURING A STALL TEST.
ALWAYS BLOCK THE FRONT WHEELS AND APPLY
THE SERVICE AND PARKING BRAKES DURING
THE TEST.
STALL TEST PROCEDURE
(1) Connect tachometer to engine.
(2) Check and adjust transmission fluid level.
(3) Start and run engine until transmission fluid
reaches normal operating temperature.
(4) Block front wheels.
(5) Fully apply service and parking brakes.
(6) Open throttle completely and record maximum
engine rpm registered on tachometer. It will take
from 3 to 10 seconds to reach maximum rpm. How-
ever, once maximum rpm has been achieved,do not
hold wide open throttle for more than 5 sec-
onds.
CAUTION: Stalling the converter causes a rapid in-
crease in fluid temperature. To avoid fluid overheat-
ing, hold wide open throttle for no more than 5
seconds after reaching peak rpm. In addition, if
more than one stall test is required, run the engine
at 1000 rpm with the transmission in Neutral for at
least 20 seconds to cool the fluid.
(7) Stall speeds should be in 1700-2150 rpm range.
CAUTION: If engine exceeds 2150 rpm, release ac-
celerator pedal immediately as transmission clutch
slippage is occurring.
(8) Shift transmission into Neutral. Run engine for
20-30 seconds at 1000 rpm to cool fluid. Then stop
engine, shift transmission into Park and release
brakes.
(9) Refer to Stall Test Diagnosis.
STALL TEST DIAGNOSIS
Stall Speed Too Low
Low stall speeds with a properly tuned engine in-
dicate a torque converter overrunning clutch prob-
lem. The condition should be confirmed by road
testing prior to converter replacement.The converter overrunning clutch is slipping when
stall speeds are 250 to 350 rpm below specified min-
imum.
A converter overrunning clutch failure will result
in sluggish acceleration in all speed ranges. It will
also require greater than normal throttle opening to
maintain cruising speeds.
Stall Speed Too High
If stall speed exceeds 2150 rpm, transmission
clutch slippage is occurring.
Stall Speed Normal But Acceleration Is Sluggish
If stall speeds are within specified range but abnor-
mal throttle opening is required for acceleration, or
to maintain cruise speeds, the converter overrunning
clutch is seized. The torque converter will have to be
replaced.
Converter Noise During Test
A whining noise caused by fluid flow is normal dur-
ing a stall test. However, loud metallic noises indi-
cate a damaged converter. To confirm that noise is
originating from the converter, operate the vehicle at
light throttle in Drive and Neutral on a hoist and lis-
ten for noise from the converter housing.
AIR PRESSURE TEST
Air pressure testing can be used to check clutch
and band operation with the transmission either in
the vehicle, or on the work bench as a final check af-
ter overhaul.
Air pressure testing requires that the oil pan and
valve body be removed from the transmission.
The servo and clutch apply passages are shown in
Figure 8.
Air Test Procedure
(1) Place one or two fingers on the clutch housing
and apply air pressure through front clutch apply
passage (Fig. 8). Piston movement can be felt and a
soft thud heard as the clutch applies.
(2) Place one or two fingers on the clutch housing
and apply air pressure through rear clutch apply
passage (Fig. 8). Piston movement can be felt and a
soft thud heard as the clutch applies.
(3) Apply air pressure to the front servo apply pas-
sage. The servo rod should extend and cause the
band to tighten around the drum. Spring tension
should release the servo when air pressure is re-
moved.
(4) Apply air pressure to the rear servo apply pas-
sage. The servo rod should extend and cause the
band to tighten around the drum. Spring tension
should release the servo when air pressure is re-
moved.
21 - 74 30RH/32RH TRANSMISSION DIAGNOSISJ