1995 JEEP XJ engine

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

Fig. 29 System SchematicÐYJ Models with 2.5L Engine
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Fig. 30 System SchematicÐYJ Models with 4.0L Engine
JFUEL SYSTEM GENERAL DIAGNOSIS 14 - 43

Fig. 31 System SchematicÐXJ Models with 2.5L Engine
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Fig. 32 System SchematicÐXJ Models with 4.0L Engine
JFUEL SYSTEM GENERAL DIAGNOSIS 14 - 45

AUTOMATIC SHUTDOWN (ASD) RELAY TESTING
To perform a complete test of the ASD relay and its
circuitry, refer to the DRB scan tool and appropriate
Powertrain Diagnostics Procedures manual. To test
the relay only, refer to RelaysÐOperation/Testing in
this section of the group.
CAMSHAFT POSITION SENSOR TEST
Refer to Group 8D, Ignition Systems, for Camshaft
Position Sensor testing.
ENGINE COOLANT TEMPERATURE SENSOR TEST
To perform a complete test of the engine coolant
temperature sensor and its circuitry, refer to DRB
scan tool and appropriate Powertrain Diagnostics
Procedures manual. To test the sensor only, refer to
the following:
Disconnect wire harness connector from engine
coolant temperature sensor (Fig. 33).
Test the resistance of the sensor with a high input
impedance (digital) volt-ohmmeter. The resistance
should be less than 1000 ohms with the engine at its
correct operating temperature. Refer to the Coolant
Temperature Sensor/Manifold Air Temperature Sen-
sor resistance chart. Replace the sensor if it is not
within the range of resistance specified in the chart.
Test continuity of the wire harness. Do this be-
tween the Powertrain Control Module (PCM) wire
harness connector terminal-2 and the sensor connec-
tor terminal. Also test continuity of wire harness ter-
minal-4 to the sensor connector terminal. Repair the
wire harness if an open circuit is indicated.
INTAKE MANIFOLD AIR TEMPERATURE 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. To test the
sensor only, refer to the following:
Disconnect the wire harness connector from the in-
take manifold air temperature sensor (Figs. 34 or
35).
Test the resistance of the sensor with an input im-
pedance (digital) volt-ohmmeter. The resistance
should be less than 4000 ohms with the engine at op-
erating temperature. The longer the engine idles, the
warmer the intake manifold temperature will be-
come. Refer to the Coolant Temperature Sensor/Man-
ifold Air Temperature Sensor resistance chart.
Replace the sensor if it is not within the range of re-
sistance specified in the chart.
Fig. 33 Engine Coolant Temperature SensorÐ
Typical
SENSOR RESISTANCE (OHMS)ÐCOOLANT
TEMPERATURE SENSOR/MANIFOLD AIR
TEMPERATURE
Fig. 34 Air Temperature SensorÐ2.5L Engine
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Test the resistance of the wire harness. Do this be-
tween the powertrain control module (PCM) wire
harness connector terminal-2 and the sensor connec-
tor terminal. Also test terminal-4 to the sensor con-
nector terminal. Repair the wire harness as
necessary if the resistance is greater than 1 ohm.
FUEL PUMP RELAY TESTING
For testing this relay, refer to RelaysÐOperation/
Testing in this section of the group.
MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR
TEST
To perform a complete test of the MAP sensor and
its circuitry, refer to DRB scan tool and appropriate
Powertrain Diagnostics Procedures manual. To test
the sensor only, refer to the following:
Inspect the MAP sensor vacuum hose connections
at the throttle body and sensor. Repair as necessary.
CAUTION: When testing, do not remove the electri-
cal connector from MAP sensor (Fig. 36). Be sure
that the MAP sensor harness wires are not dam-
aged by the test meter probes.
Test the MAP sensor output voltage at the MAP
sensor connector between terminals A and B (as
marked on the sensor body) (Fig. 37). With the igni-
tion switch ON and the engine OFF, output voltage
should be 4-to-5 volts. The voltage should drop to 1.5-
to-2.1 volts with a neutral-hot idle speed condition.
Test the powertrain control module (PCM) (termi-
nal-5) for the same voltage described above to verify
the wire harness condition. Repair as necessary.
Test MAP sensor supply voltage at sensor connec-
tor between terminals A and C (Fig. 37) with the ig-
nition ON and engine OFF. The voltage should be
approximately 5 volts (60.5V). Five volts (60.5V)should also be at terminal-6 of the PCM wire harness
connector. Repair or replace the wire harness as nec-
essary.
Test the MAP sensor ground circuit at sensor con-
nector terminal-A (Fig. 37) and PCM connector termi-
nal-4. Repair the wire harness if necessary.
Test the MAP sensor ground circuit at the PCM
connector between terminal-4 and terminal-11 with
an ohmmeter. If the ohmmeter indicates an open cir-
cuit, inspect for a defective sensor ground connection.
Refer to Group 8W, Wiring for location of engine
grounds. If the ground connection is good, replace the
PCM. If terminal-4 has a short circuit to 12 volts,
correct this condition before replacing the PCM.
CRANKSHAFT POSITION SENSOR TEST
Refer to Group 8D, Ignition Systems for test proce-
dures.
Fig. 35 Air Temperature SensorÐ4.0L EngineFig. 36 MAP SensorÐTypical
Fig. 37 MAP Sensor Connector TerminalsÐTypical
JFUEL SYSTEM GENERAL DIAGNOSIS 14 - 47

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
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