diag code DODGE TRUCK 1993 Service User Guide

•

ELECTRICAL
8A - 15 a

CASE
GROUND
CAPACITOR
ALTERNATOR ~L FIELD
TERMINALS

A
142-DG/OR BATTERY
VOLTAGE K20-DG
—!

GROUND
CASE

GROUND
til

ALTERNATOR BATTERY
TERMINAL ENGINE
CONTROLLER TO ENGINE
CONTROLLER TERMINAL
51

LESS
THAN
BATTERY VOLTAGE A21
DB-
.....
IGNITION SWITCH
20 AMP FUSE
AUTO
AH ^

SHUTDOWN POWER
RELAY
DISTRIBUTION

\
CENTER TEST
AMMETER JUMPER WIRE
TO GROUND
TEST
VOLTMETER
GO
5—n
DISCONNECTED
ALTERNATOR OUTPUT WIRE GROUND

ACC
Bl
OFF
RUN OFF
START*T

|ACC

CARBON
PILE RHEOSTAT
J938A-18

Fig.
2 Generator Current Output Test—Typical

CAUTION:
Do not
connect
blue
A142
lead
of
wiring

to ground.
Refer
to
Group
8W -
Wiring
Diagrams
for
more
information.

TEST
(1) Start engine. Immediately after starting reduce
engine speed to idle. (2) Adjust carbon pile and engine speed in incre­
ments until a speed of 1250 rpm and voltmeter read­
ing of 15 volts is obtained.

CAUTION:
Do not
allow
voltage
meter
to
read
above
16 volts.

(3) The ammeter reading must be within limits
shown in generator specifications in back of this
group for that size of generator being tested.

RESULTS
(1) If reading is less than specified and generator
output wire resistance is not excessive, the generator
should be replaced. Refer to Group 8B - Generator
Service for information.
(2) After current output test is completed reduce
engine speed, turn off carbon pile and turn off igni­
tion switch.
(3) Disconnect negative cable from battery. (4) Remove test ammeter, voltmeter, tachometer
and carbon pile. (5) Remove Jumper Wire (Fig. 2).
(6) Connect generator output wire to generator
BAT terminal post. Tighten nut to 5-6 Nnn (45-75 in.

lbs.).

(7) Connect negative cable to battery.
(8) Use DRB II Scan Tool to erase diagnostic trou­
ble code.

USING
ON-BOARD
DIAGNOSTIC
SYSTEM
OPERATION
OF
ON-BOARD
DIAGNOSTIC

SYSTEM

The Powertrain Control Module monitors critical
input and output circuits of the charging system
making sure they are okay. Some are checked contin­
uously and some are only checked under certain con­
ditions.
If the OBD system senses that one of the critical
circuits is bad, it will consider this a real problem
and put a DTC into memory. Each input and output
circuit monitored by the OBD system has its own

DTC.
The DTC will stay in memory as long as the
circuit continues to be bad. If the problem does not
occur again after the code is put into memory, the
Powertrain Control Module will clear the memory af­
ter 50 to 100 engine starts.

•

ELECTRICAL
8A - 17
DIAGNOSTIC
TROUBLE
CODES

Diagnostic trouble codes are 2 digit numbers
flashed on Malfunction Indicator lamp (Check En­
gine) that identify which circuit is bad. In most cases
they do not identify which component in a circuit is
bad. A DTC description can be read using the DRB II scan tool. Refer to Group 14 - Fuel Systems for more
information. Therefore, a DTC is only a result, not
necessarily the reason for the problem. However, in
some cases, as a result of the design of the driveabil- ity test procedure, a DTC can be the reason for the
problem. It is important that the test procedure be followed in order to understand what the DTC of the
on-board diagnostic system are trying to tell.

HOW
TO
USE
MALFUNCTION
INDICATOR
(CHECK

ENGINE)
LAMP
FOR
FAULT
CODES
To activate this function cycle the ignition switch
on-off-on-off-on within 5 seconds and any DTC stored
in the Powertrain Control Module will be displayed.
The Check Engine lamp will display a DTC by flash­ ing on and off. There is a short pause between
flashes and a longer pause between digits. All codes
displayed are two digit numbers with a four second
pause between codes. An example of a code is as follows:
(1) Lamp on for 2 seconds, then turns off.
(2) Lamp flashes 4 times pauses and then flashes

1.
(3) Lamp pauses for 4 seconds, flashes 4 times,
pauses and then flashes 7 times.
The two codes are 41 and 47. Any number of codes
can be displayed (maximum of 8 faults can be stored) as long as they are in memory. The lamp will flash
until all of them (including 55) are displayed (55 =
End of test).

CHARGING
SYSTEM
FAULT
CODES
See Generator Fault Code Chart for fault codes
which apply to the charging system. Refer to the
Powertrain Diagnostic Procedures Manual to diag­
nose an On-Board Diagnostic System, Fault Code.
GENERATOR
DIAGNOSTIC
TROUBLE
CODE
(DTC)

DTC
Type
Malfunction

Indicator
Lamp
Circuit
When
Monitored

By
the
Logic

Module
When
Put Into
Memory
Actuator

Test
Sensor

Read
Test

41 Fault
Yes
Generator Field

Control
(Charging
System)
All the
time
when
the ignition switch

is
on.
An
open or shorted condition in
the generator
field

control circuit.
Yes

None

46 Fault
Yes
Charging
System

Voltage
All the
time
when the

engine
is
running.
If the
battery
sense
voltage is
more than 1 volt
above
the

desired
control voltage for
more than 20
seconds.
None

Yes

47 Fault
Yes
Charging
System

Voltage
Engine
rpm
above

1,500 rpm Battery voltage
1
volt
less

than set point during engine
operation and no
change
in

voltage
during
internal
PCM
test performed on generator field.
None

Yes

J938A-20

•

VEHICLE
SPEED
CONTROL SYSTEM
8H - 7
TEST
PROCEDURES

INDEX

page

Checking
for
Diagnostic
Trouble
Code
7

General
Information
7
Inoperative
System
7

Road
Test
7

Speed
Control
Cable Adjustment—Diesel Engine
. 9

Speed
Control
Cable
Attachment
10

GENERAL
INFORMATION

Before starting diagnosis and repair procedures for
a speed control malfunction, verify that the speed
control wire harness is properly connected to all con­ nectors. Refer to Diagnosis Chart.

ROAD
TEST
Road test vehicle to verify reports of speed control
system malfunction. The road test should include at­
tention to the speedometer. Speedometer operation should be smooth and without flutter at all speeds. Flutter in the speedometer indicates a problem
which might cause surging in the speed control sys­
tem. The cause of any speedometer deficiencies should be corrected before proceeding.

INOPERATIVE SYSTEM
If road test verifies a system problem and the
speedometer operates properly, check for:
• loose electrical and vacuum connections at the
servo.

• check for correct installation of the vacuum check
valve in the hose from servo to vacuum source (Gas
Engine Only). The word VAC on the valve must
point toward the vacuum source. • corrosion that should be removed from electrical
terminals and a light coating of Mopar Multi-Pur­
pose Grease, or equivalent, applied. • secure attachment of both ends of speed control ca­

ble.

CHECKING
FOR DIAGNOSTIC TROUBLE CODE
(1) When trying to verify a speed control system
electrical problem, use a DRB II Scan Tool to find
the cause. Refer to Powertrain Diagnostic Procedures manual. If the DRBII is not available, the Diagnostic Trou­
ble Code (DTC) may be determined with the follow­ ing method: (a) With key inserted in ignition switch, cycle
switch to ON position 3 times. On third cycle, leave
switch in ON position. (b) After switch has been cycled 3 times, observe
Malfunction Indicator Lamp (CHECK ENGINE) on instrument cluster. If a DTC is present, the code
page

Speed
Control
Cable Attachment—Servo
10

Stop Lamp Switch Test
9

Vacuum Supply Test
....................... 9

Vehicle Speed
Control
Switch Test
. 9

Vehicle Speed
Control
System
Electrical
Tests
... 7

Vehicle Speed Sensor Test
7
will be displayed in a series of flashes representing
digits.
Three flashes in rapid succession, a slight
pause, then 4 flashes in rapid succession would in­ dicate DTC 34.
(2) If a DTC 34 is observed, perform the tests in
the sections Electrical Tests at Servo and Electrical
Tests at Powertrain Control Module.
If a DTC 15 is observed, perform the test for a
faulty Vehicle Speed Sensor.
(3) If a fault code 11 is observed (Diesel only), per­
form the test for a faulty engine speed sensor. Refer
to the Powertrain Diagnostics Procedures Manual.
(4) Correct any problems found when performing
these tests and recheck for DTC if changes were made.

VEHICLE SPEED SENSOR TEST
For testing of the Vehicle Speed Sensor and related
components refer to the Powertrain Diagnostic Proce­
dures manual.

VEHICLE SPEED CONTROL SYSTEM ELECTRICAL
TESTS
Vehicle speed control systems may be tested using
two different methods. One involves the use of the DRBII Scan Tool. If this test method is desired,
please refer to the Powertrain Diagnostic Procedures manual. The other test method uses a voltmeter. The volt­
meter method is described in the following tests.
If any information is needed concerning wiring, re­
fer to Group 8W - Wiring Diagrams.

CAUTION:
When test probing
for
voltage
or
conti­nuity
at
electrical
connectors, care must
be
taken
not
to
damage connector, terminals,
or
seals.
If

these components
are
damaged,
intermittent
or
complete system
failure
may
occur.
ELECTRICAL
TESTS
AT
SERVO
(1) Turn ignition switch to ON position.
(2) Push speed control switch to ON position.
(3) Connect the negative lead of a voltmeter to a
good chassis ground near the servo.

•

WIRING DIAGRAMS
8W
- 1
CONTENTS

page page
COMPONENT IDENTIFICATION
.............
9
SPLICE LOCATIONS
29

GENERAL
INFORMATION
1
WIRING DIAGRAMS AD-BODY
37

GENERAL
INFORMATION
INDEX
page

Circuit
Identification
2

Component
Identification
3

Connectors
3
Fusible Links
3

Harness
Repair
3

Locating
A
System
or
Component
2
page
Secondary
Ignition
Wiring
1

Splice Locations
3
Symbols
and
Fuses
5

Troubleshooting
Wiring
Problems
3

Wire Code
Identification
2

Wiring
Diagram Sheets
and
Indexes
1

The wiring diagrams contain
the
latest information
available
at
time
of
publication. Throughout
out
this
group references
may
be
made
to a
particular vehicle
by letter
or
number designation.
A
chart showing
the
breakdown
of
these designations
is
included
in the
Introduction Section
of
this service manual.

SECONDARY
IGNITION WIRING
Secondary ignition wiring
is
shown
in
Figures
1

and 2.
For
information
on
ignition systems
or
distrib­
utor operation refer
to
Group
8D
Ignition Systems.
SPARK
PLUGS

RIGHT
BANK

3.9L
SIX-CYLINDER
ENGINE

DISTRIBUTOR—CLOCKWISE
ROTATION
FIRING
ORDER
1-6-5-4-3-2
RN755
Fig.
1
Secondary
Ignition Wiring 3.9L
Engine

WIRING DIAGRAM SHEETS AND INDEXES
The wiring diagram sheets
are
organized
so
that
systems relating
to the
basic vehicle
and all of
its op­

tions
are
shown. Add-on
or
non-factory options
are
SPARK
PLUGS

LEFT
BANK

EIGHT
CYLINDER
DISTRIBUTOR-CLOCKWISE
ROTATION
FOR
318
AND
360
CUBIC
INCH
ENGINES

FIRING
ORDER-1-8^-3-63-7-2 RP899 Fig.
2
Secondary
Ignition Wiring 5.2L and 5.9L

Engine
not covered.
The
diagram pages
are
identified
by a

sheet number which
is
located
at the
lower right
or

left hand corner
of
each sheet. Page numbers
at the

top
of
each page
do not
apply
to
diagram sheets.
Diagram sheets show
all
information relating
to

the system. This includes feeds, grounds, switch
in­
ternal circuity, connectors, splices,
and
pin
identifica­
tion
for
controllers
and
modules.
In certain instances
a
wire
may be
referenced
to

another sheet. When this happens,
the
wire will
be

identified
as to
where
it is
going.
The index used
for the
diagrams
is
located
at the

beginning
of the
diagrams.
It
covers
all
systems shown
in the
diagrams
and is in
alphabetical order.

WIRING
DIAGRAMS

8W
- 2
WIRING
DIAGRAMS

•
WIRE CODE
IDENTIFICATION

Each wire shown in the diagrams contains a code
(Fig. 3) which identifies the main circuit, part of the
main circuit, gauge of wire, and color. The color is shown as a two letter code which can be identified by
referring to the Wire Color Code Chart (Fig. 4). If
the wire has a tracer and it is a standard color an asterisk will follow the main wire color. If the tracer
is non-standard the main wire color will have a slash (/) after it followed by the tracer color. 18
LB/YL*
COLOR
OF
WIRE

(Light
Blue
with
Yellow
Tracer)
.
GAUGE
OF
WIRE
(18
Gauge)

PART
OF
AAAIN CIRCUIT

(Varies
Depending
on
Equipment)

AAAIN CIRCUIT
IDENTIFICATION
918W-16

Fig.
3
Wire
Color
Code
Identification

CIRCUIT IDENTIFICATION
All circuits in the diagrams use an alpha/numeric
code to identify the, wire and its function. To identify
which circuit code applies to a system, refer to the
Circuit Identification Code Chart. This chart shows
the main circuits only and does not show the second­ ary codes that may apply to some models.
COLOR

CODE COLOR
STANDARD
TRACER

COLOR COLOR

CODE
COLOR
STANDARD

TRACER
CODE
BL BLUE WT
OR ORANGE

BK
BK
BLACK
WT PK
PINK
BK
OR WT

BR
BROWN
WT RD
RED WT
DB DARK
BLUE WT
TN
TAN WT
DG DARK
GREEN WT
VT

VIOLET
WT
GY GRAY
BK

WT

WHITE
BK

LB
LIGHT

BLUE
BK

YL YELLOW

BK

LG
LIGHT

GREEN
BK

*

WITH
TRACER

918W-136
Fig.
4
Wire
Color
Code
Chart

LOCATING
A
SYSTEM
OR
COMPONENT
To locate a system or component in the diagrams,
refer to the alphabetical index at the front of the di­ agrams. Determine the diagram sheet number. Sheet
numbers are located at the lower right or left hand
corner of each sheet. Page numbers at the top of
the page do not apply to diagram sheets. The diagram index identifies the main system and
all components that relate to that system. There are
also sections of the index that identify specific com­
ponents only (for example modules, lamps, etc.). Re-

MAIN
CIRCUIT IDENTIFICATION

CIRCUIT
DESCRIPTION
CIRCUIT
DESCRIPTION

A
Battery
Feed: Fused and Unfused
P
Power
Assist
System:
Locks,
Mirrors

B
ABS
System Q Power
Assist
System: Windows

C
Air Conditioning System

R
Airbag System

D
CCD
(+),
CCD
(-)
S
Air Suspension, Automatic Load Leveling

E
Interior
Lamp
Illumination
T Electronic Automatic Transaxle
F
Battery
Feed: Fused and Unfused
V
Windshield Wipers and Washers,

G
Sensors,
Sending Units, Switches Vehicle Speed Control System

K
Powertrain
Central
Module W Power
Assist
System: Windows

L
Exterior
Lighting, Stop Lamp Switch
X
Horn, Radio, Radio Speakers, Power Locks
M
Interior
Lamps
Z
Ground Circuits: Includes power and signal

Interior
Lamps

grounds
for PCM

938W-17

•

WIRING
DIAGRAMS
8W - 3 fer to a components name in the index if you are
unclear as to what a system may be called.
Diagram pages are arranged starting with the bat­
tery and fuses. Then working into charging, starting, and ignition systems. After this they start at the
front of the vehicle and work to rear of the vehicle.
The diagrams end with connector identification

pages.

COMPONENT
IDENTIFICATION
To find a components actual location on the vehicle
refer to the wiring and components section index. This section shows the wire harness routing and the compo­
nents location in the vehicle. When using this section
refer to the wiring diagrams for the general location of
the component. Then use the component identification index to locate the proper figure number.

SPLICE
LOCATIONS
Splices are indicated in the wiring diagrams by a
diamond with splice circuit code within it (Fig. 5 ex­ ample 1). If there is more than one splice per circuit
splice code a small box will be connected to the dia­
mond with the splice number in it (Fig. 5 example 2). To locate a splice in the wire harness determine
the splice number from the wiring diagrams, then re­
fer to the splice location index. This section shows
the general location of the splice in the harness.

EXAMPLE
1
EXAMPLE
2 918W-18

Fig.
5 Wiring
Splice
Examples

CONNECTORS
The connectors shown in the diagram are viewed from
the terminal end unless otherwise specified. For view­ ing bulkhead and engine controller connectors refer to
the back of the wiring diagrams. This area shows major connectors for pin and cavity identification.

TROUBLESHOOTING
WIRING
PROBLEMS
When troubleshooting wiring problems there are
six steps which can aid in the procedure. The steps
are listed and explained below. (1) Verify the problem.
(2) Verify any related symptoms. Perform opera­
tional checks on components in the same circuit as the problem area. Refer to the wiring diagram fuse
application chart for circuit information. (3) Analyze the symptoms. Use the wiring dia­
grams to determine what the circuit is doing, where
the problem most likely is occurring and where the diagnosis will continue. (4) Isolate the problem area. (5) Repair the problem.
(6) Verify proper operation. For this step check for
proper operation of all items on the circuit repaired. Refer to the wiring diagram fuse application chart.

FUSIBLE
LINKS
Vehicle wiring harnesses are equipped with fusible

links.
For protection against harness damage in the
event of a short. Fusible links are color coded as to
wire gauge size. Refer to the fusible link chart for color and gauge identification (Fig. 6).
Wire and
Gauge
Color
Code
Color

12 Ga.
BK
Black

14 Ga.
RD
Red

16 Ga.
DB
Dark
Blue

18 Ga.
GY
Gray

20 Ga.
OR
Orange

22 Ga.
WT
White
918W-19

Fig.
6 Fusible
Link
Chart

HARNESS
REPAIR

FUSIBLE
LINK
REPLACEMENT

CAUTION:
Do not replace blown fusible
links
with
a

standard
wire.
Only
use fusible type
wire
with
hyp-

alon
insulation or
damage
to the electrical
system
could
occur.
Also
make
sure
correct
gauge
of
wir­
ing
is
used.
Refer to the wiring
diagrams
for proper

gauge
and
color.

When a fusible link blows it is important to find
out what the problem is. They are placed in the elec­
trical system for protection against shorts to ground
that can be caused by a component or various wiring
failures. Do not just replace the fusible link to correct the problem.
When diagnosing a faulty fusible link it is impor­
tant to check the wire carefully. In some instances
the link may be blown and it will not show through the insulation, the wire should be checked over its
entire length for internal breaks.
(1) Disconnect battery negative cable.
(2) Cut out the blown portion of the fusible link.
(3) Strip 1 inch of insulation from each end of the
existing fusible link.
(4) Place a piece of heat shrink tubing over one
side of the fusible link. Make sure the tubing will be
long enough to cover and seal the entire repair area.
(5) Cut a replacement piece of fusible link approx­
imately two inches longer than the piece removed. (6) Remove one inch of insulation from each end of
the replacement fusible link.

FUEL
TUBE

REMOVAL

QUICK
CONNECT

FITTING

PUSH
PUSH PUSH

INSTALLATION

X
PUSH

/

•PUSH

PLASTIC

RETAINER
J9314-100

Fig. 19 Removing/Installing Quick-Connect Fitting (8) If pressure falls below 24 psi, it must deter­
mined if a fuel injector, the fuel module mounted fuel
pressure regulator or a fuel tube/line is leaking. (9) Again, start engine and bring to normal oper­
ating temperature.
(10) Shut engine off.
(11) Checking for fuel injector leakage: Clamp
off the rubber hose portion of tool 6539 between the
disconnected fuel tube (line) and test port inlet. If
pressure now holds at or above 24 psi, a fuel injector or the fuel rail is leaking.
Checking for fuel pressure regulator or fuel
tube leakage: Clamp off the rubber hose portion of
tool 6539 between the fuel rail and test port inlet. If
pressure now holds at or above 24 psi, a leak can be
found at a fuel tube/line. If no leaks are found at fuel

tubes,
replace the fuel filter/fuel pressure regulator.

MECHANICAL MALFUNCTIONS
Mechanical malfunctions are more difficult to diag­
nose with this system. The powertrain control mod­
ule (PCM) has been programmed to compensate for
some mechanical malfunctions such as incorrect cam
timing, vacuum leaks, etc. If engine performance
problems are encountered and a diagnostic trouble code (DTC) is not displayed, the problem may be me­
chanical rather than electronic.

FUEL FILTER-3.9L/5.2L GAS ENGINE
For diesel engines, refer to Fuel/Water Separator
Filter in the Diesel Fuel Injection—Service Proce­
dures section of this group.
REMOVAL

WARNING:
THE
FUEL
SYSTEM
IS
UNDER
A
CON­
STANT
PRESSURE
(EVEN
WITH
THE
ENGINE
OFF).
BEFORE
SERVICING
THE
FUEL FILTER,
THE
FUEL
SYSTEM
PRESSURE
MUST
BE
RELEASED.

The fuel filter is located under the vehicle and near
the fuel tank. It is mounted to the frame rail (Fig.
20). (1) Perform Fuel System Pressure Release proce­

dure.
(2) Disconnect negative battery cable from battery.
(3) Raise and support vehicle.
(4) Remove and discard both fuel hose-to-fuel filter
hose clamps. (5) Wrap a shop towel around hoses to absorb fuel.
Remove hoses at filter. (6) Remove filter from frame.
FUEL
HOSES
HOSE
CLAMPS
.
FILTER
MOUNTING
BOLT
FUEL

FILTER

J9214-68

Fig.
20
Fuel
Filter—3.9U5.2L
Engine

INSTALLATION

CAUTION:
The
tubes/hoses used
on
fuel
injected

vehicles
are of a
special construction. This
is due

to
the
higher
fuel
pressures
and the
possibility
of
contaminated
fuel
in
this system.
If it is
necessary
to replace these tubes/hoses, only tubes/hoses marked EFM/EFI
may be
used.

CAUTION:
The
hose clamps used
on
fuel
injected

vehicles
are of a
special rolled edge construction
to
prevent
the
edge
of the
clamp from cutting into
the
hose.
Only these rolled edge
type
clamps
may be

used
in
this system.
All
other types
of
clamps
may

cut into
the
hoses
and
cause high pressure
fuel
leaks.

(1) Install fuel filter to frame rail. Tighten mount­
ing bolt to 8 N»m (75 in. lbs.) torque. (2) Install new original equipment clamps to fuel

hoses.

14
- 30
FUEL
SYSTEM

INPUTS

OUTPUTS
POWERTRAIN
CONTROL
MODULE
DRB
II

SCAN
TOOL

SPEED

CONTROL

BRAKE

SWITCH
A/C
LOW

PRESSURE
CUTOFF
SWITCH VEHICLE

SPEED
SENSOR PARK/NEUTRAL
SWITCH TORQUE CONVERTER
CLUTCH SOLENOID
MALFUNCTION

INDICATOR
LAMP
m
HEATED
i

*OXYGEN SENSOR ENGINE
COOLANT
yy
BATTERY
TEMPERATURE

SENSOR
MAP SENSOR

i—r
CHARGE
AIR
TEMPERATURE
SENSOR
AIR CHARGE
TEMPERATURE
SENSOR
DISTRIBUTOR

WITH
CAMSHAFT
r
POSITION
SENSOR
(|
TACHOMETER

A/C
CLUTCH RELAY
AUTO
SHUTDOWN
RELAY OVERDRIVE
SOLENOID
IDLE AIR
CONTROL MOTOR
SPEED

CONTROL
SHIFT

INDICATOR

LAMP

EMISSION

CONTROL SOLENOIDS
IGNITION
COIL
OVERDRIVE
OVERRIDE SWITCH
ASD

SENSE
FUEL
INJECTORS
PARK
THROTTLE

SOLENOID
GENERATOR CRANKSHAFT
POSITION FUEL
PUMP
RELAY
J9314-117

Fig.
1 Multi-Port
Fuel
Injection
Components—Except
Diesel

gine Control System. It is also comprised of the PCM Outputs (engine control devices that the are operated
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 Multi-Port Fuel Injec­
tion—General Diagnosis—Except Diesel section of
this group for DTC information.

POWERTRAIN
CONTROL MODULE (PCM)
The Powertrain Control Module (PCM) (Fig. 2) op­
erates the fuel system. The PCM was formerly re­
ferred to as the SBEC or engine controller. The PCM is a pre-programmed, dual microprocessor digital computer. It regulates ignition timing, air-fuel ratio, emission control devices, charging system, speed con­trol, air conditioning compressor clutch engagement
A/C
CLUTCH RELAY STARTER RELAY
TORQUE CONVERTER CLUTCH RELAY
AUTO
SHUTDOWN RELAY
FUEL PUMP RELAY
DATA UNK
CONNECTOR
POWERTRAIN

CONTROL MODULE
J9314-164

Fig.
2 Powertrain Control
Module
(PCM) Location and idle speed. The PCM can adapt its programming
to meet changing operating conditions.
The PCM receives input signals from various
switches and sensors. Based on these inputs, the
PCM regulates various engine and vehicle operations

•

FUEL SYSTEM
14-31 through different system components. These compo­
nents are referred to as Powertrain Control Module
(PCM) Outputs. The sensors and switches that pro­
vide inputs to the PCM are considered Powertrain Control Module (PCM) Inputs.
The PCM adjusts ignition timing based upon in­
puts it receives from sensors that react to: engine rpm, manifold absolute pressure, engine coolant tem­
perature, throttle position, transmission gear selec­
tion (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, engine 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:
• Generator output • A/C request (if equipped with factory A/C)
• A/C select (if equipped with factory A/C)
• Auto shut down (ASD) sense
• Charge air temperature sensor
• Battery voltage
• Brake switch
• Engine coolant temperature sensor
• Crankshaft position sensor • Ignition circuit sense (ignition switch in run posi­
tion)
• Manifold absolute pressure (MAP) sensor
• Overdrive/override switch
• Oxygen sensor(s)
• Park/neutral switch (auto, trans, only)
• SCI receive (DRB II connection) • Speed control resume switch
• Speed control set switch • Speed control on/off switch
• Camshaft position sensor signal
• Throttle position sensor
• Vehicle speed sensor
• Sensor return
• Power ground
• Signal ground Powertrain Control Module (PCM) Outputs:
• A/C clutch relay
• Idle air control (IAC) motor
• Auto shut down (ASD) relay
• Generator field
• Malfunction indicator lamp
• Service reminder indicator lamp
• EGR valve control solenoid • Fuel injectors
• Fuel pump relay
• Ignition coil • EVAP canister purge solenoid
• SCI transmit (DRB II connection)
• Shift indicator lamp (manual transmission only)
• Speed control vacuum solenoid
• Speed control vent solenoid
• Tachometer (on instrument panel, if equipped) The powertrain control module (PCM) contains a
voltage convertor. This converts battery voltage to a
regulated 8.0 volts. It is used to power the crankshaft
position sensor and camshaft position sensor. The
PCM also provides a five (5) volt supply for the man­ ifold absolute pressure (MAP) sensor and throttle po­
sition sensor (TPS).

AIR
CONDITIONING
(A/C)
CONTROLS-PCM
INPUT
The A/C control system information applies to fac­
tory installed air conditioning units. 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
control 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 powertrain control module (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 idle air control (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 re­ lay, deactivating the A/C compressor clutch.

AUTOMATIC SHUT DOWN
(ASD)
SENSE-PCM 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 engine compartment (Fig. 2). It is used
to connect the oxygen sensor(s) heater element, igni­
tion coil, generator field winding and fuel injectors to 12 volt + power supply. This input is used only to sense that the ASD relay
is energized. If the powertrain control module (PCM)
does not see 12 volts at this input when the ASD
should be activated, it will set a diagnostic trouble
code (DTC).

•

FUEL SYSTEM
14 - 37 used only on vehicles equipped with the 5.9L heavy
duty cycle (HDC) engine. Refer to Group 25, Emis­
sion Control System for information.

EVAP CANISTER PURGE SOLENOID-PCM

OUTPUT
Refer to Group 25, Emission Control System. See
EVAP Canister Purge Solenoid.

FUEL INJECTORS-PCM
OUTPUT
The fuel injectors are attached to the fuel rail (Fig.

15).
3.9L engines use six injectors. 5.2L and 5.9L en­
gines use eight injectors. The nozzle ends of the injectors are positioned into
openings in the intake manifold just above the in­
take valve ports of the cylinder head. The engine
wiring harness connector for each fuel injector is equipped with an attached numerical tag (INJ 1, INJ 2 etc.). This is used to identify each fuel injector with
its respective cylinder number. The injectors are energized individually in a se­
quential order by the powertrain control module (PCM). The PCM will adjust injector pulse width by
switching the ground path to each individual injector
on and off. Injector pulse width is the period of time
that the injector is energized. The PCM will adjust injector pulse width based on various inputs it re­
ceives. During start up, battery voltage is supplied to the
injectors through the ASD relay. When the engine is
operating, voltage is supplied by the charging sys­
tem. The PCM determines injector pulse width based on various inputs.
FUEL

INJECTOR
J9214-30

Fig.
15
Fuel
injectors—Typical
MALFUNCTION INDICATOR LAMP-PCM OUTPUT

The malfunction indicator lamp (formerly referred
to as the check engine lamp) illuminates at the bot­
tom of the instrument panel each time the ignition key is turned on. It will stay on for three seconds as a bulb test. 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.

IGNITION COIL-PCM 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 front of the
right cylinder head (Fig. 16 or 17). Refer to Group 8D, Ignition System for additional
information.

Fig.
16 Ignition Coii-3.9U5.2U5.9L
LDC-Gas
Engine

SCI
TRANSMIT—PCM OUTPUT
SCI Transmit is the serial data communication
transmit circuit for the DRB II scan tool. The power- train control module (PCM) transmits data to the DRB II through the SCI Transmit circuit.