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Unread 09-18-2006, 01:38 AM   #1
Cerealdaemon
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1988 FSJ Wagoneer 
 
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GEN Light

Other than the Alternator, which I've had checked twice, both on and off of the vehicle, what would cause the GEN light on the dash to come on?

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Unread 09-18-2006, 11:40 AM   #2
balloo93
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Batt not holding a charge is an easy one.

The harder would be a problem with the ECU reading the voltage.
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Unread 09-18-2006, 11:59 AM   #3
96XJTech
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This light came on in mine last year, and it happened when I was driving in a heavy downpour, and went through a somwhat deep puddle. My battery was cracked and leaking, and the water splashing onto it caused my voltage to drop rapidly to about 9, my radar detector and radio turned off as their wasn't enough power to run those, and I lost my power steering. My GEN light also illuminated. This only lasted for about 15 seconds, and after it dried out, returned to normal. I replaced the battery, and haven't had that problem since.
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Unread 09-18-2006, 03:34 PM   #4
Cerealdaemon
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if it is the ECU, which I'm starting to think that it might be, based on what I've deduced from the symptoms of all the different things I've tried fixing to get this to work, what do I do to fix that?

Do I have to replace the computer to get a new ECU?

Or is the ECU a stand alone unit?
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Unread 09-18-2006, 03:42 PM   #5
balloo93
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Sorry, ECU is the computer. aka PCM or ECM. Engine Cotrol Unit, Power Control Module, or Engine Control Module.

I'd trace the wires from eth alt to the computer and make sure there aren't any issues with them. The Alt is regulated by the computer, so if it's getting screwy voltage/amp then it will react to that.
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Unread 09-18-2006, 03:45 PM   #6
Cerealdaemon
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thats kinda what I figured, i'm working on tracing the wires, but the run into the loom and distinguishing those two wires from the rest of the wires in there is no small task

Balloo, do you know where I can find a pinout diagram for the three big connectors that go into the computer?

then I'll just whip out the ohmmeter and I'll know.
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Unread 09-18-2006, 03:47 PM   #7
Cerealdaemon
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also, I'm wondering if i should limp my 96 up to the dealership and have them reprogram the ECU, and see what that'll do. the recall affects me, so I might give that a try, what do you think?
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Unread 09-18-2006, 03:49 PM   #8
balloo93
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I'd go the dealer route to be honest with you. I can try to find the pin out, but I can't gaurentee sucess.
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Unread 09-18-2006, 04:32 PM   #9
balloo93
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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 generator
field terminals (Gen. Source +) at the back of the
generator.

The amount of DC current produced by the generator
is controlled by the EVR (field control) circuitry
contained within the PCM. This circuitry is connected
in series with the second rotor field terminal
and ground.

A battery temperature sensor, located in the battery
tray housing, is used to sense battery temperature.
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 magnetic
field. The PCM then compensates and regulates
generator current output accordingly.

All vehicles are equipped with On-Board Diagnostics
(OBD). All OBD-sensed systems, including EVR
(field control) circuitry, are monitored by the PCM.
Each monitored circuit is assigned a Diagnostic Trouble
Code (DTC). The PCM will store a DTC in electronic
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 temperature
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 signal
to activate the lamp is sent via the CCD bus circuits.
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 reason,
the entire assembly must be replaced.
OPERATION
As the energized rotor begins to rotate within the
generator, the spinning magnetic field induces a current
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 externally,
different generators with different output ratings
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 Generator
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 defective
drive pulley; incorrect, worn, damaged or misadjusted
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 temperature
and control battery charging rate. This temperature
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 temperature
increases, resistance in the sensor decreases
and the detection voltage at the PCM increases.
The BTS is also used for OBD II diagnostics. Certain
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.
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Unread 09-18-2006, 04:33 PM   #10
balloo93
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ELECTRONIC VOLTAGE REGULATOR

DESCRIPTION
The Electronic Voltage Regulator (EVR) is not a
separate component. It is actually a voltage regulating
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 generator
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 voltage
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 capability
to ground the field control wire 100% of the time
(full field) to achieve the target voltage. If the charging
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:

² the generator lamp (if equipped) is illuminated
with the engine running
² the voltmeter (if equipped) does not register
properly
² an undercharged or overcharged battery condition
occurs.
Remember that an undercharged battery is often
caused by:
² accessories being left on with the engine not
running
² 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 Procedures
service manual and the DRB scan tool. Perform
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 Generator
Removal/Installation section of this group for
torque specifications.

(5) Inspect generator drive belt condition and tension.
Tighten or replace belt as required. Refer to
Belt Tension Specifications in Group 7, Cooling System.

(6) Inspect automatic belt tensioner (if equipped).
Refer to Group 7, Cooling System for information.

(7) Inspect generator electrical connections at generator
field, battery output, and ground terminal (if
equipped). Also check generator ground wire connection
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 system,
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 continuously
and some are checked only under certain conditions.
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 connectors.

(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+ terminal.

(6) Remove B+ terminal mounting nut at rear of
generator (Fig. 4). Disconnect terminal from generator.

(7) Disconnect field wire connector at rear of generator
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)

INSTALLATION
(1) Position generator to engine and snap field
wire connector into rear of generator.

(2) Install B+ terminal to generator mounting
stud. Tighten mounting nut to 8.5 N·m (75 in. lbs.)
torque.

(3) If equipped, snap plastic cover to B+ terminal.

(4) LHD Vehicles: Install generator fasteners and
tighten as follows:

² Generator upper mounting bolt-55 N·m (41 ft.
lbs.) torque.
² Generator lower pivot bolt/nut-55 N·m (41 ft.
lbs.) torque.
CAUTION: Never force a belt over a pulley rim
using a screwdriver. The synthetic fiber of the belt
can be damaged.
CAUTION: When installing a serpentine accessory
drive belt, the belt MUST be routed correctly. The
water pump will be rotating in the wrong direction if
the belt is installed incorrectly, causing the engine
to overheat. Refer to belt routing label in engine
compartment, or refer to Belt Schematics in Group
7, Cooling System.

(5) LHD Vehicles: Install generator drive belt.
Refer to Group 7, Cooling System for procedures.

(6) RHD Vehicles: Install upper nut (generator
adjustment nut) and both belt adjustment bolts.
Install generator lower nut/bolt.

(7) RHD Vehicles: On vehicles equipped with RHD,
the generator is used to adjust the serpentine belt.
Refer to Group 7, Cooling System for belt routing,
belt adjustment and bolt tightening procedures.

(8) Install negative battery cable to battery.


BATTERY TEMPERATURE SENSOR
The battery temperature sensor is located under
vehicle battery (Fig. 5) and is attached to a mounting
hole on battery tray.

REMOVAL
(1) Remove battery. Refer to Group 8A, Battery for
procedures.
(2) Disconnect sensor pigtail harness from engine
wire harness.
(3) Pry sensor straight up from battery tray
mounting hole.

INSTALLATION
(1) Feed pigtail harness through hole in top of battery
tray and press sensor into top of battery tray.
(2) Connect pigtail harness.
(3) Install battery. Refer to Group 8A, Battery for
procedures.

SPECIFICATIONS
GENERATOR RATINGS
TYPE PART NUMBER RATED SAE AMPS ENGINES MINIMUM TEST AMPS
DENSO 56041685AA 117 4.0L 88
DENSO 56041565AA 81 4.0L 57
DENSO 56005684AB 81 2.5L 57
DENSO 56005685AC 117 2.5L 88
DENSO 56041822AA 124 2.5L/4.0L 90

TORQUE CHART
Right Hand Drive= RHD, Left Hand Drive= LHD.
Description Torque
Generator Mounting Bolt—LHD—2.5L/4.0L
Engine . . . . . . . . . . . . . . . . . . 55 N·m (41 ft. lbs.)
Generator Pivot Bolt/Nut—LHD—2.5L/4.0L
Engine . . . . . . . . . . . . . . . . . . 55 N·m (41 ft. lbs.)
Battery Terminal Nut—LHD or
RHD . . . . . . . . . . . . . . . . . . 8.5 N·m (75 in. lbs.)
Description Torque
Ground Terminal Nut—LHD or
RHD . . . . . . . . . . . . . . . . . . 8.5 N·m (75 in. lbs.)
Harness Hold-down Nut—LHD or
RHD . . . . . . . . . . . . . . . . . . 8.5 N·m (75 in. lbs.)
Field Terminal Nuts—LHD or
RHD . . . . . . . . . . . . . . . . . . 2.8 N·m (25 in. lbs.)
__________________
93 Sport
Beer is proof that God loves us and wants us to be happy............Ben Franklin


Specs in Profile.

http://www.cardomain.com/ride/325707/1
http://www.cardomain.com/ride/2406854/1
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