Jeep XJ. Manual — part 91
SPECIFICATIONS
STARTING SYSTEM
Starter and Solenoid
Engine Application
2.5L Diesel
Power Rating
2.2 Kilowatt
Voltage
12 Volts
Number of Fields
4
Number of Poles
4
Number of Brushes
4
Drive Type
Planetary Gear Reduction
Free Running Test Voltage
11.5 Volts
Free Running Test Maximum
Amperage Draw
160 Amperes
Free Running Test Minimum
Speed
5500 rpm
Solenoid Closing Maximum
Voltage
7.8 Volts
*Cranking Amperage Draw
test
350 Amperes
*Test at operating temperature. Cold engine, tight (new) engine, or heavy oil will
increase starter amperage draw.
TORQUE SPECIFICATIONS
DESCRIPTION
TORQUE
Engine Mount Throughbolt . . . . 65 N·m (48 ft. lbs.)
Engine Mount Upper Sill Plate Nuts . . . . . 41 N·m
(30 ft. lbs.)
Engine Mount to Engine Mounting Bolts . . 61 N·m
(45 ft. lbs.)
Lower Engine Mount Bolts . . . . 54 N·m (40 ft. lbs.)
Stater Motor (B+) Terminal . . . . 27 N·m (20 ft. lbs.)
Starter Motor Retaining Bolts . . 27 N·m (20 ft. lbs.)
Starter Motor Support Bracket Nuts . . . . . . 10 N·m
(90 in. lbs.)
Steering Shaft Pinch Bolt . . . . . 49 N·m (36 ft. lbs.)
Track Bar Support Bracket Bolts . . . . . . . 125 N·m
(92 ft. lbs.)
8B - 4
STARTING SYSTEMS
XJ
2000 JEEP CHEROKEE
CHARGING SYSTEM
TABLE OF CONTENTS
page
page
DESCRIPTION AND OPERATION
CHARGING SYSTEM. . . . . . . . . . . . . . . . . . . . . . . 1
GENERATOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
BATTERY TEMPERATURE SENSOR . . . . . . . . . . . 2
ELECTRONIC VOLTAGE REGULATOR . . . . . . . . . . 2
DIAGNOSIS AND TESTING
CHARGING SYSTEM. . . . . . . . . . . . . . . . . . . . . . . 2
ON-BOARD DIAGNOSTIC TEST FOR
CHARGING SYSTEM . . . . . . . . . . . . . . . . . . . . . 3
REMOVAL AND INSTALLATION
GENERATOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
BATTERY TEMPERATURE SENSOR . . . . . . . . . . . 5
SPECIFICATIONS
DESCRIPTION AND OPERATION
CHARGING SYSTEM
DESCRIPTION
The charging system consists of:
• Generator
• Electronic Voltage Regulator (EVR) circuitry
within the Powertrain Control Module (PCM)
• Ignition switch (refer to Group 8D, Ignition Sys-
tem for information)
• Battery (refer to Group 8A, Battery for informa-
tion)
• Battery temperature sensor
• Generator Lamp (if equipped)
• Check Gauges Lamp (if equipped)
• Voltmeter (refer to Group 8E, Instrument Panel
and Gauges for information)
• Wiring harness and connections (refer to Group
8W, Wiring for information)
OPERATION
The charging system is turned on and off with the
ignition switch. The system is on when the engine is
running and the ASD relay is energized. When the
ASD relay is on, voltage is supplied to the ASD relay
sense circuit at the PCM. This voltage is connected
through the PCM and supplied to one of the genera-
tor field terminals (Gen. Source +) at the back of the
generator.
The amount of DC current produced by the gener-
ator is controlled by the EVR (field control) circuitry
contained within the PCM. This circuitry is con-
nected in series with the second rotor field terminal
and ground.
A battery temperature sensor, located in the bat-
tery tray housing, is used to sense battery tempera-
ture. This temperature data, along with data from
monitored line voltage, is used by the PCM to vary
the battery charging rate. This is done by cycling the
ground path to control the strength of the rotor mag-
netic field. The PCM then compensates and regulates
generator current output accordingly.
All vehicles are equipped with On-Board Diagnos-
tics (OBD). All OBD-sensed systems, including EVR
(field control) circuitry, are monitored by the PCM.
Each monitored circuit is assigned a Diagnostic Trou-
ble Code (DTC). The PCM will store a DTC in elec-
tronic memory for certain failures it detects. Refer to
On-Board Diagnostics in Group 25, Emission Control
System for more DTC information.
The Check Gauges Lamp (if equipped) monitors:
charging system voltage, engine coolant tempera-
ture and engine oil pressure. If an extreme condition
is indicated, the lamp will be illuminated. This is
done as reminder to check the three gauges. The sig-
nal to activate the lamp is sent via the CCD bus cir-
cuits. The lamp is located on the instrument panel.
Refer to Group 8E, Instrument Panel and Gauges for
additional information.
GENERATOR
DESCRIPTION
The generator is belt-driven by the engine using a
serpentine type drive belt. It is serviced only as a
complete assembly. If the generator fails for any rea-
son, the entire assembly must be replaced.
OPERATION
As the energized rotor begins to rotate within the
generator, the spinning magnetic field induces a cur-
rent into the windings of the stator coil. Once the
XJ
CHARGING SYSTEM
8C - 1
generator begins producing sufficient current, it also
provides the current needed to energize the rotor.
The Y type stator winding connections deliver the
induced AC current to 3 positive and 3 negative
diodes for rectification. From the diodes, rectified DC
current is delivered to the vehicle electrical system
through the generator battery terminal.
Although the generators appear the same exter-
nally, different generators with different output rat-
ings are used on this vehicle. Be certain that the
replacement generator has the same output rating
and part number as the original unit. Refer to Gen-
erator Ratings in the Specifications section at the
back of this group for amperage ratings and part
numbers.
Noise emitting from the generator may be caused
by: worn, loose or defective bearings; a loose or defec-
tive drive pulley; incorrect, worn, damaged or misad-
justed
fan
drive
belt;
loose
mounting
bolts;
a
misaligned drive pulley or a defective stator or diode.
BATTERY TEMPERATURE SENSOR
DESCRIPTION
The Battery Temperature Sensor (BTS) is attached
to the battery tray located under the battery.
OPERATION
The BTS is used to determine the battery temper-
ature and control battery charging rate. This temper-
ature data, along with data from monitored line
voltage, is used by the PCM to vary the battery
charging rate. System voltage will be higher at colder
temperatures and is gradually reduced at warmer
temperatures.
The PCM sends 5 volts to the sensor and is
grounded through the sensor return line. As temper-
ature increases, resistance in the sensor decreases
and the detection voltage at the PCM increases.
The BTS is also used for OBD II diagnostics. Cer-
tain faults and OBD II monitors are either enabled
or disabled, depending upon BTS input (for example,
disable purge and enable Leak Detection Pump
(LDP) and O2 sensor heater tests). Most OBD II
monitors are disabled below 20°F.
ELECTRONIC VOLTAGE REGULATOR
DESCRIPTION
The Electronic Voltage Regulator (EVR) is not a
separate component. It is actually a voltage regulat-
ing circuit located within the Powertrain Control
Module (PCM). The EVR is not serviced separately. If
replacement is necessary, the PCM must be replaced.
OPERATION
The amount of DC current produced by the gener-
ator is controlled by EVR circuitry contained within
the PCM. This circuitry is connected in series with
the generators second rotor field terminal and its
ground.
Voltage is regulated by cycling the ground path to
control the strength of the rotor magnetic field. The
EVR circuitry monitors system line voltage (B+) and
battery temperature (refer to Battery Temperature
Sensor for more information). It then determines a
target charging voltage. If sensed battery voltage is
0.5 volts or lower than the target voltage, the PCM
grounds the field winding until sensed battery volt-
age is 0.5 volts above target voltage. A circuit in the
PCM cycles the ground side of the generator field up
to 100 times per second (100Hz), but has the capabil-
ity to ground the field control wire 100% of the time
(full field) to achieve the target voltage. If the charg-
ing rate cannot be monitored (limp-in), a duty cycle
of 25% is used by the PCM in order to have some
generator output. Also refer to Charging System
Operation for additional information.
DIAGNOSIS AND TESTING
CHARGING SYSTEM
The following procedures may be used to diagnose
the charging system if:
• the generator lamp (if equipped) is illuminated
with the engine running
• the voltmeter (if equipped) does not register
properly
• an undercharged or overcharged battery condi-
tion occurs.
Remember that an undercharged battery is often
caused by:
• accessories being left on with the engine not
running
• a faulty or improperly adjusted switch that
allows a lamp to stay on. See Ignition-Off Draw Test
in Group 8A, Battery for more information.
INSPECTION
To perform a complete test of the charging system,
refer to the appropriate Powertrain Diagnostic Proce-
dures service manual and the DRB scan tool. Per-
form the following inspections before attaching the
scan tool.
(1) Inspect the battery condition. Refer to Group
8A, Battery for procedures.
(2) Inspect condition of battery cable terminals,
battery posts, connections at engine block, starter
solenoid and relay. They should be clean and tight.
Repair as required.
8C - 2
CHARGING SYSTEM
XJ
DESCRIPTION AND OPERATION (Continued)
(3) Inspect all fuses in both the fuseblock and
Power Distribution Center (PDC) for tightness in
receptacles. They should be properly installed and
tight. Repair or replace as required.
(4) Inspect generator mounting bolts for tightness.
Replace or tighten bolts if required. Refer to the Gen-
erator Removal/Installation section of this group for
torque specifications.
(5) Inspect generator drive belt condition and ten-
sion. Tighten or replace belt as required. Refer to
Belt Tension Specifications in Group 7, Cooling Sys-
tem.
(6) Inspect automatic belt tensioner (if equipped).
Refer to Group 7, Cooling System for information.
(7) Inspect generator electrical connections at gen-
erator field, battery output, and ground terminal (if
equipped). Also check generator ground wire connec-
tion at engine (if equipped). They should all be clean
and tight. Repair as required.
ON-BOARD DIAGNOSTIC TEST FOR CHARGING
SYSTEM
The Powertrain Control Module (PCM) monitors
critical input and output circuits of the charging sys-
tem, making sure they are operational. A Diagnostic
Trouble Code (DTC) is assigned to each input and
output circuit monitored by the On-Board Diagnostic
(OBD) system. Some circuits are checked continu-
ously and some are checked only under certain con-
ditions.
For DTC information, refer to Diagnostic Trouble
Codes in Group 25, Emission Control System. This
will include a complete list of DTC’s including DTC’s
for the charging system.
REMOVAL AND INSTALLATION
GENERATOR
REMOVAL
WARNING: DISCONNECT NEGATIVE CABLE FROM
BATTERY BEFORE REMOVING BATTERY OUTPUT
WIRE (B+ WIRE) FROM GENERATOR. FAILURE TO
DO SO CAN RESULT IN INJURY OR DAMAGE TO
ELECTRICAL SYSTEM.
(1) Disconnect negative battery cable at battery.
(2) Remove generator drive belt. Refer to Group 7,
Cooling System for procedures.
(3) Left Hand Drive (LHD) Vehicles Only: Remove
generator pivot and mounting bolts/nut (Fig. 1) or
(Fig. 2). Position generator for access to wire connec-
tors.
(4) Right
Hand
Drive
(RHD)
Vehicles
Only:
Remove upper nut (generator adjustment nut) and
both belt adjustment bolts (Fig. 3). Remove generator
lower nut/bolt. Position generator for access to wire
connectors.
(5) If equipped, unsnap plastic cover from B+ ter-
minal.
(6) Remove B+ terminal mounting nut at rear of
generator (Fig. 4). Disconnect terminal from genera-
tor.
(7) Disconnect field wire connector at rear of gen-
erator by pushing on connector tab.
(8) Remove generator from vehicle.
Fig. 1 Remove/Install Generator—2.5L Engine
1 – UPPER MOUNTING BRACKET
2 – GENERATOR
3 – UPPER BOLT
4 – LOWER BOLT
XJ
CHARGING SYSTEM
8C - 3
DIAGNOSIS AND TESTING (Continued)
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