1995 JEEP YJ diagram

plugged catalytic convertor.
(27) If equipped with automatic transmission, ver-
ify that electrical harness is firmly connected to park/
neutral safety switch. Refer to Automatic
Transmission section of Group 21.
(28) Verify that the harness connector is firmly
connected to the vehicle speed sensor (Fig. 26).
(29) Verify that fuel pump module wire connector
is firmly connected to harness connector.
(30) Inspect fuel hoses at fuel pump module for
cracks or leaks (Fig. 27).
(31) Inspect transmission torque convertor housing
(automatic transmission) or clutch housing (manual
transmission) for damage to timing ring on drive
plate/flywheel.
(32) Verify that battery cable and solenoid feed
wire connections to the starter solenoid are tight andclean. Inspect for chaffed wires or wires rubbing up
against other components (Fig. 28).
POWERTRAIN CONTROL MODULE (PCM) 60-WAY
CONNECTOR
For PCM 60-way connector wiring schematics, refer
to Group 8W, Wiring Diagrams.
Fig. 27 Fuel Pump Module Connector and Fuel HosesÐTypical
Fig. 25 Oxygen Sensor LocationÐTypical
Fig. 26 Vehicle Speed SensorÐTypical
14 - 40 FUEL SYSTEM GENERAL DIAGNOSISJ

PCM SYSTEM SCHEMATICS
Powertrain control system schematics for the 2.5L
4-cylinder and 4.0L 6-cylinder engines are shown in
figures 29, 30, 31 and 32.
These schematics are displayed as a quick refer-
ence only. They are not intended to be all-inclusive.
Refer to the Wiring Diagrams section for detailed in-
formation.
Fig. 28 Starter Solenoid ConnectionsÐTypical
JFUEL SYSTEM GENERAL DIAGNOSIS 14 - 41

EXTENDED IDLE SWITCH TEST
OPTIONAL POLICE PACKAGE ONLY
OPERATION
The extended idle switch is used to raise the en-
gine idle speed to approximately 1000 rpm when the
shifter is in either the Park or Neutral position. A
rocker-type 2-wire switch (extended idle switch) is
mounted to the instrument panel.This switch is
available only with 4.0L engine when supplied
with the optional police package.
TESTING
The extended idle switch will control a ground cir-
cuit going to the powertrain control module (PCM).
When a ground signal (through this switch) has been
received at pin number 10 in the PCM, engine idle
speed will increase.
Bring the engine to normal operating temperature
and turn the extended idle switch to the ON position.
Engine speed should now increase to approximately
1000 rpm when the shifter is in either the Park or
Neutral position. If engine speed does not increase,
apply a good ground to pin number 10 at the PCM
using a small paper clip. Be careful not to damage
the wiring with the paper clip. If the engine speed
now increases, it can be assumed that the PCM is
functioning correctly. Check the instrument panel
mounted switch for a closed ground circuit when in
the ON position. If the engine speed will not increase
after applying a ground to pin number 10, replace
the PCM. Refer to Group 8W, Wiring Diagrams for
circuit and wiring information.
THROTTLE POSITION SENSOR (TPS) TEST
To perform a complete test of the sensor and its cir-
cuitry, refer to DRB scan tool and appropriate Pow-
ertrain Diagnostics Procedures manual. To test the
sensor only, refer to the following:
The throttle position sensor (TPS) can be tested
with a digital voltmeter. The center terminal of the
TPS is the output terminal (Figs. 38 or 39).
With the ignition key in the ON position, back-
probe the TPS connector. Check the TPS output volt-
age at the center terminal wire of the connector.
Check this at idle (throttle plate closed) and at wide
open throttle (WOT). At idle, TPS output voltage
should must be greater than 200 millivolts. At wide
open throttle, TPS output voltage must be less than
4.8 volts. The output voltage should increase gradu-
ally as the throttle plate is slowly opened from idle to
WOT.
TORQUE CONVERTER CLUTCH RELAY TEST
To test the relay only, refer to RelaysÐOperation/
Testing in this section of the group. To test the
torque converter clutch circuit and related compo-nents, refer to the appropriate Powertrain Diagnostic
Procedures manual for operation of the DRB scan
tool.
VEHICLE SPEED SENSOR TEST
To perform a complete test of the sensor and its cir-
cuitry, refer to DRB scan tool and appropriate Pow-
ertrain Diagnostics Procedures manual.
OXYGEN SENSOR (O2S) HEATING ELEMENT TEST
To perform a complete test of the O2S sensor (Fig.
40) and its circuitry, refer to DRB scan tool and ap-
propriate Powertrain Diagnostics Procedures manual.
To test the sensor only, refer to the following:
The oxygen sensor heating element can be tested
with an ohmmeter as follows:
With the sensor at room temperature 25 degrees C
(77 degrees F), disconnect the O2S sensor connector.
Connect the ohmmeter test leads across the white
wire terminals of the sensor connector. Resistance
should be between 5 and 7 ohms. Replace the sensor
if the ohmmeter displays an infinity (open) reading.
Fig. 38 TPS TestingÐ2.5L Engine
Fig. 39 TPS TestingÐ4.0L Engine
14 - 48 FUEL SYSTEM GENERAL DIAGNOSISJ

(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

(23) Install input shaft on output shaft (Fig. 59).
Be sure output shaft hub is fully seated in pilot bear-
ing.
OUTPUT SHAFT AND CLUSTER GEAR
INSTALLATION
(1) Mount intermediate plate in vise (Fig. 24).
(2) Lubricate cluster gear journal and rear bearing
with petroleum jelly or gear lubricant.
(3) Install cluster gear rear bearing in intermedi-
ate plate (Fig. 81). Be sure snap ring groove in bear-
ing is rearward as shown.
(4) Start cluster gear into bearing (Fig. 57). Then
hold bearing and push gear into place. Use plastic or
rawhide mallet to seat bearing if necessary.
(5) Start output shaft rear bearing in intermediate
plate. Push shaft rearward and tap intermediate
plate with mallet to seat bearing.
(6) Install snap rings on cluster and output shaft
rearbearings only (Fig. 82). Do not install front
bearing snap rings at this time.
(7) Install reverse idler gear and shaft (Fig. 83).(8) Position rear bearing retainer over output shaft
and rear bearing.Be sure bearing retainer tab is
engaged in reverse idler shaft notch (Fig. 84).
(9) Install and tighten rear bearing retainer bolts
to 18 Nzm (13 ft-lbs).
SHIFT RAIL AND FORK INSTALLATION
The shift rail interlock pins, balls and plugs must
be installed in the correct sequence for proper shift-
ing. Refer to the installation diagram (Fig. 85) during
assembly.
Coat the intermediate plate shift rail bores
and the interlock balls, pins and plugs with a
thick covering of petroleum jelly before assem-
bly. The jelly will hold the interlock compo-
nents in place making installation easier. Use a
pencil magnet to hold and insert the interlocks.
Then use a small screwdriver to push the inter-
lock components into place.
(1) Coat reverse rail interlock pin with petroleum
jelly and install pin in rail (Fig. 86).
(2) Install reverse shift rail in intermediate plate
(Fig. 87).
Fig. 81 Installing Cluster Gear Rear Bearing
Fig. 82 Installing Rear Bearing Snap Rings
Fig. 83 Installing Reverse Idler Gear And Shaft
Fig. 84 Installing Rear Bearing Retainer
21 - 56 AX 15 MANUAL TRANSMISSIONJ

HEATING AND AIR CONDITIONING TEST PROCEDURES
INDEX
page page
A/C Compressor Clutch..................... 15
A/C Compressor Clutch Relay................ 15
A/C Compressor Clutch Relay................ 16
Air Conditioning ControlsÐXJ Vehicles......... 15
Air Conditioning ControlsÐYJ Vehicles......... 16
Blower Motor............................ 17
Blower Motor Switch....................... 16Compressor Clutch........................ 16
Fin Sensing Cycling Clutch Switch............. 15
Heater Diagnosis......................... 17
Low-Pressure High-Pressure Cut-Off Switch..... 15
Low-Pressure High-Pressure Cut-Off Switch..... 16
Thermostatic Control....................... 16
AIR CONDITIONING CONTROLSÐXJ VEHICLES
The A/C Compressor Clutch is controlled by several
components: the Pressure Cut-Off Switch, Cycling
Clutch Switch, Clutch Relay and Powertrain Control
Module (PCM).
Powertrain Control Module may delay A/C clutch
engagement up to 30 seconds.
Refer to Group 8W Wiring Diagrams for wiring and
terminals. Use volt ohmmeter to test switches.
A/C COMPRESSOR CLUTCH
The clutch assembly consists of a stationary elec-
tromagnetic coil, hub bearing pulley assembly, and
clutch plate. When the coil is energized the plate is
magnetically engaged with the pulley and turns the
compressor shaft.
A/C COMPRESSOR CLUTCH TEST
(1) Unplug clutch coil connector.
(2) Connect a jumper wire from the battery posi-
tive post to the clutch coil terminal. The clutch
should engage, if not leave jumper wire connected
and go to next step.
(3) Connect a jumper wire from clutch coil frame to
chassis ground. The clutch should engage if not re-
pair clutch coil ground or replace coil.
A/C COMPRESSOR CLUTCH RELAY
The A/C compressor clutch relay controls the 12-
volt source to the A/C clutch. The relay is activated
when the PCM receives a A/C request signal from the
fin-sensed cycling clutch switch. The PCM then sends
a ground signal to the relay. The relay is activated
and sends 12-volts to the clutch coil which energizes
the clutch. The relay is located in the power distribu-
tion center.
COMPRESSOR CLUTCH RELAY TEST
For test procedure refer to Powertrain Diagnostic
Service Manual for A/C clutch relay circuit test.
LOW-PRESSURE HIGH-PRESSURE CUT-OFF
SWITCH
The pressure cut-off switch is located on the filter
drier and is wired in series with compressor clutch.
The switch interrupts the power to the compressor
clutch circuit when the pressure drops to 193 kPa (28
psi) or increases above 3100 to 3375 kPa (450 to 490
psi).
PRESSURE CUT-OFF SWITCH TEST
(1) Verify system has correct refrigerant charge.
(2) Turn ignition switch to RUN, A/C blower switch
to ON and control set to MAX.
(3) Unplug pressure cut-off switch and test feed
circuit from select switch. It should be battery volt-
age if not, repair open to select switch.
(4) Test for continuity between the switch termi-
nals. If continuity is not present recover refrigerant
from the system. Replace switch, evacuate and re-
charge system.
FIN SENSING CYCLING CLUTCH SWITCH
The switch is attached to the evaporator coil with
the temperature sensing probe inserted into the coil
fins. This switch prevents condensate water on the
evaporator coil from freezing. It does this by sending
signals to the PCM to cycling the compressor clutch
on and off.
FIN-SENSED CYCLING CLUTCH SWITCH TEST
Test area ambient temperature should be around
21ÉC (70ÉF) for test.
(1) Verify system has correct refrigerant charge.
(2) Start Engine and turn on A/C.
(3) If the compressor clutch cycles ON and OFF 2
to 3 times per minute the cycling clutch switch is
normal. The ambient temperature should be between
20ÉC-30ÉC (68ÉF-90ÉF). Above 32ÉC (90ÉF) the com-
pressor clutch may stay engaged (non cycling) due to
the high heat load, this condition is normal. If the
compressor clutch fails to engage go to next step.
(4) Disconnect wiring harness connector from
switch. With a volt meter test feed circuit from cut-
JHEATING AND AIR CONDITIONING 24 - 15

off switch for battery voltage. If no voltage is present
test pressure cut-off switch. If voltage is present go
to next step.
(5) With ohmmeter test harness connector ground
circuit for continuity to ground. If circuit is open, (no
continuity) repair ground circuit. If circuit test OK
and clutch does not engage refer to Powertrain Diag-
nostic Service Manual for A/C clutch circuit test.
AIR CONDITIONING CONTROLSÐYJ VEHICLES
The air conditioning circuit consists of 3 segments;
battery supply, blower motor and compressor clutch.
The 3 segments have a common connection point at
the blower switch.
The power supply circuit extends from the HTR/
FAN fuse to the blower switch. From the blower
switch, battery feed is routed to the blower motor
and compressor clutch circuit.
Refer to Group 8W Wiring Diagrams for wiring
schematic and terminals. Use volt ohmmeter to test
switches.
COMPRESSOR CLUTCH
The clutch assembly consists of a stationary elec-
tromagnetic coil, hub bearing pulley assembly, and
clutch plate. When the coil is energized the plate is
magnetically engaged with the pulley and turns the
compressor shaft.
COMPRESSOR CLUTCH TEST
(1) Unplug clutch coil connector.
(2) Connect jumper wire from battery positive post
to clutch coil connector. The clutch should engage, if
not leave jumper wire connected and go to next step.
(3) Connect jumper wire from clutch coil frame to
chassis ground. The clutch should engage, if not re-
pair clutch coil ground or replace coil.
A/C COMPRESSOR CLUTCH RELAY
The A/C compressor clutch relay controls the 12-
volt source to the A/C clutch. The relay is activated
when the PCM receives a A/C request signal. The
PCM then sends a ground signal to the relay. The re-
lay is activated and sends 12-volts to the clutch coil
which energizes the clutch. The relay is located in
the power distribution center.
COMPRESSOR CLUTCH RELAY TEST
For test procedure refer to Powertrain Diagnostic
Service Manual for A/C clutch relay circuit test.
LOW-PRESSURE HIGH-PRESSURE CUT-OFF
SWITCH
The pressure cut-off switch is located on the filter
drier and is wired in series with compressor clutch.
The switch interrupts the power to the compressorclutch circuit when the pressure drops to 193 kPa (28
psi) or increases above 3100 to 3375 kPa (450 to 490
psi).
PRESSURE CUT-OFF SWITCH TEST
(1) Turn ignition switch to RUN, A/C blower switch
to ON and control set to MAX.
(2) Unplug pressure cut-off switch connector and
test feed circuit from the thermostatic, should be bat-
tery voltage. If not, proceed to thermostatic control
tests.
(3) Test for continuity between the switch termi-
nals. If continuity is not present recover refrigerant
system, replace switch, evacuate and recharge sys-
tem.
THERMOSTATIC CONTROL
Cycling of the compressor and therefore the tem-
perature of the outlet air is regulated by the thermo-
static control. A thermal sensor extends from the
control to the evaporator housing. When the temper-
ature of the evaporator drops below the set tempera-
ture, the thermostatic control opens the clutch
circuit. The circuit remains open until evaporator
temperature rises above the set temperature.
THERMOSTATIC CONTROL TEST
(1) Turn ignition switch to RUN, A/C blower switch
to ON and thermostatic control set to MAX cool.
(2) Test thermostatic control feed terminal from
blower switch, should be battery voltage. If not re-
pair open from blower switch.
(3) Test thermostatic control output terminal to
pressure cut-out switch, should be battery voltage. If
not, replace thermostatic control.
BLOWER MOTOR SWITCH
The blower switch controls blower motor speed.
The blower motor segment consists of the 3 wires
from the blower switch to the motor. Through the
switch, the 3 wires connect the motor brushes to bat-
tery supply. When connected to battery feed, the sep-
arate brushes provide the 3 blower speeds LO, MED,
and HIGH.
BLOWER MOTOR SWITCH TEST
(1) Turn ignition to RUN position.
(2) Test battery side of fuse for battery voltage. If
not, repair open from ignition switch.
(3) Test A/C blower switch feed circuit from fuse
box should be battery voltage. If not, repair open
from fuse panel.
(4) Test A/C blower switch LO terminal with
blower switch in LO, should be battery voltage. If
not, replace switch.
(5) Test A/C blower switch MED terminal with
blower switch in MED, should be battery voltage. If
not, replace switch.
24 - 16 HEATING AND AIR CONDITIONINGJ

(6) Test A/C blower switch HIGH terminal with
blower switch in HIGH, should be battery voltage. If
not, replace switch.
BLOWER MOTOR
The A/C blower motor is attached to the evaporator
housing mounted under the instrument panel. The
motor has a ground wire and 3 wires connect to the
motor brushes. When voltage is applied to the sepa-
rate brushes it provides the 3 blower speeds LO,
MED, and HIGH.
BLOWER MOTOR TEST
Turn ignition switch to RUN for voltage tests and
turn ignition switch to OFF for resistance test.
(1) Test A/C blower motor ground terminal should
be 0 ohms. If not, repair ground circuit.
(2) Test A/C blower motor connector LO terminal
with blower switch in LO, should be battery voltage.
If not repair open from blower switch. If the blower
motor is still inoperative replace motor.
(3) Test A/C blower motor connector MED terminal
with blower switch in MED, should be battery volt-
age. If not repair open from blower switch. If the
blower motor is still inoperative replace motor.
(4) Test A/C blower motor connector HIGH termi-
nal with blower switch in HIGH, should be battery
voltage. If not, repair open from blower switch. If the
blower motor is still inoperative, replace motor.
HEATER DIAGNOSIS
On LHD XJ vehicles a water valve controls coolant
flow to the heater core. The valve is vacuum oper-
ated. When vacuum is applied, the valve opens and
coolant is directed through the heater core and back
to the engine. When the water valve is closed (no
vacuum applied) coolant flow bypasses the heater
core back to the engine.
The heating system receives its battery feed from
the fuse box. On YJ vehicles the feed circuit runs to
the HEATER/OFF switch and then to the BLOWER
switch. On XJ vehicles the feed circuit runs to the
HEAT/MODE switch and then to the BLOWER
switch.
The blower speed is controlled by the blower switch
and blower resistors. With the switch in LO, battery
voltage is supplied to the motor through all of the re-
sistors. The motor runs slowly. When the blower
switch is moved to a higher speed, battery voltage in-
creases to the blower motor which increase its speed.
This is accomplished by bypassing some of the blower
resistors. When the switch is in HI, blower resistors
are bypassed and battery voltage is applied directly
to the blower motor.
The following chart has been developed for quick
reference.
Refer to the Group 8W Wiring Diagrams for com-
plete wiring schematic.
JHEATING AND AIR CONDITIONING 24 - 17