check engine DODGE TRUCK 1993 Service Manual PDF

8A
- 14
ELECTRICAL

CASE
GROUND
FIELD

TERMINALS

142-DG/OR
BATTERY
VOLTAGE


ALTERNATOR
CASE

GROUND
GROUND ALTERNATOR
BATTERY
TERMINAL
ENGINE
CONTROLLER TO ENGINE
CONTROLLER TERMINAL
51

LESS
THAN

"BATTERY VOLTAGE
m^mm i
A21 DB-
20
AMP FUSE
A14
RD


AUTO

SHUTDOWN
RELAY
IGNITION
SWITCH

POWER

DISTRIBUTION
CENTER
JUMPER WIRE TO GROUND TEST
AMMETER TEST

VOLTMETER
2
i

DISCONNEaED

ALTERNATOR
OUTPUT
WIRE
ACC

OFF
J938A-17
CARBON
PILE
RHEOSTAT
Fig.
1 Generator Output
Wire
Resistance
Test
(Typical)

(2) Adjust engine speed and carbon pile to main­
tain 20 amperes flowing in circuit. Observe voltmeter
reading. Voltmeter reading should not exceed 0.5
volts.

RESULTS
If a higher voltage drop is indicated, inspect, clean
and tighten all connections between generator BAT
terminal and battery Positive post. A voltage drop
test may be performed at each connection to locate
connection with excessive resistance. If resistance
tested satisfactorily, reduce engine speed, turn off carbon pile and turn off ignition switch.
(1) Disconnect negative cable from battery.
(2) Remove test ammeter, voltmeter, carbon pile,
and tachometer. (3) Remove "Jumper Wire".
(4) Connect generator output wire to generator
BAT terminal post. Tighten to 5 to 6 Nnn (45 to 75

in.
lbs.). (5) Connect negative cable to battery.
(6) Use DRB II Scan Tool to erase diagnostic trou­
ble code.

CURRENT
OUTPUT
TEST
Current output test determines whether or not gen­
erator is capable of delivering its rated current out­
put.
PREPARATION

(1) Before starting any tests make sure vehicle has
a fully charged battery. Test and procedures on how
to check for a fully charged battery are shown in
Battery section of this Group,
(2) Disconnect negative cable from battery.
(3) Disconnect generator output wire at the gener­
ator battery terminal.
(4) Connect a 0-150 ampere scale D.C. ammeter in
series between generator BAT terminal and discon­
nected generator output wire (Fig. 2). Connect posi­
tive lead to generator BAT terminal and negative
lead to disconnected generator output wire.
(5) Connect positive lead of a test voltmeter (range
0-18 volts minimum) to generator BAT terminal.
(6) Connect negative lead of test voltmeter to a
good ground.
(7) Connect an engine tachometer and connect neg­
ative cable to battery.
(8) Connect a variable carbon pile rheostat be­
tween battery terminals. Be sure carbon pile is in Open or Off position before connecting leads. See
Battery section, Load Testing for instructions.
(9) Connect one end of a Jumper Wire to ground
and with other and probe green K20 lead wire at
back of generator (Fig. 2). (This will generate a fault
code).

•

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

•

Fig.
3
Remove
or install
Wire
Connector
Assembly
CAUTION:
When
installing
serpentine
accessory

drive
belt,
the
belt
MUST
be
routed
correctly.
If not,
the engine may overheat due to the
water
pump ro­

tating
in the wrong
direction.
Refer to Group 7 -
Cooling
System
for
correct
engine
belt
routing.
The

correct
belt
with
the
correct
length
must be
used

(3) Position drive belt over all pulleys except the
idler pulley. This pulley is located between the gen­
erator and A/C compressor.
(4) Attach a socket/wrench to pulley mounting bolt
of the automatic tensioner (Fig. 1).

(5)
Rotate socket/wrench clockwise. Place belt over
idler pulley. Let tensioner rotate back into place. Re­
move wrench. Be sure belt is properly seated on all
pulleys.
(6) Check belt indexing marks. Refer to Group 7 -
Cooling, Automatic Belt Tensioner.
(7) Connect negative cable to battery.

GENERATOR
REPLACEMENT—5.9L
HDC-GAS

ENGINE
Drive belts on these engines are equipped with a
spring loaded automatic belt tensioner (Fig. 4). This
belt tensioner is used on all belt configurations. For more information, refer to Group 7 - Cooling, Belt
Removal/Installation.

REMOVAL
(1) Disconnect negative cable from battery.
(2) Attach a socket/wrench to pulley mounting bolt
of automatic tensioner (Fig. 4). The threads on this
bolt are left hand.
BATTERY/STARTER/GENERATOR
SERVICE
8B - 7

Fig.
4 Automatic Belt Tensioner—5.9L
HDC-Gas
Engine
(3) Rotate tensioner assembly counterclockwise (as
viewed from front) until tension has been relieved
from belt.
(4) Remove belt from idler pulley first.
(5) Remove belt from vehicle.
(6) Remove lower generator mounting bolt and nut
(Fig. 5).

Fig.
5 Generator
Mounting
Bolts

(7) Remove upper generator mounting bolt and re­
move generator.
(8) Remove B+ terminal nut, 2 field terminal

nuts,
ground, and harness hold down nuts (Fig. 6).
Remove wire connectors.

•

IGNITION
SYSTEMS
80 - 7
DIAGNOSTICS/SERW1CE
PROCEDURES

INDEX

page

Automatic Shut Down (ASD) Relay
7
Camshaft Position
Sensor
Test
...............
7

Crankshaft Position
Sensor
Test
8

Distributor
Cap
8

Distributor
Rotor
8
Engine
Coolant Temperature
Sensor
Test
10

General
Information
7

Ignition
Coil
8

Ignition
Secondary
Circuit
Diagnosis
10

GENERAL
INFORMATION
This section
of the
group, Diagnostics/Service Pro­
cedures, will discuss basic ignition system diagnos­
tics
and
service adjustments. For system operation
and
component identification,
refer
to the
Component Identification/System Opera­
tion section
of
this group. For removal
or
installation
of
ignition system com­
ponents, refer
to the
Component Removal/Installa­
tion section
of
this group. For other useful information, refer
to
On-Board
Di­

agnostics
in the
General Diagnosis sections
of
Group
14,
Fuel System
in
this manual. For operation
of the DRB II
Diagnostic Scan Tool,
refer
to the
appropriate Powertrain Diagnostic Proce­
dures service manual.

AUTOMATIC SHUT DOWN
(ASD)
RELAY
Refer
to
Relays—Operation/Testing
in the
Group

14,
Fuel System section
of
this service manual.

CAMSHAFT POSITION SENSOR TEST
The camshaft position sensor
is
located
in the
dis­
tributor
on all
engines. To perform
a
complete test
of
this sensor
and its

circuitry, refer
to the DRB II
diagnostic scan tool.
Also refer
to the
appropriate Powertrain Diagnostics
Procedures manual.
To
test
the
sensor only, refer
to

the following: For this test,
an
analog (non-digital) voltmeter
is needed.
Do not
remove
the
distributor connector from
the
distributor. Using small paper clips, insert
them into
the
backside
of the
distributor wire har­ ness connector
to
make contact with
the
terminals.
Be sure that
the
connector
is not
damaged when
in­
serting
the
paper clips. Attach voltmeter leads
to

these paper clips. (1) Connect
the
positive (
+
)
voltmeter lead into
the sensor output wire. This
is at
done
the
distribu­ tor wire harness connector.
For
wire identification,
refer
to
Group
8W,
Wiring Diagrams.
page

Ignition
Timing
12

Intake Manifold Charge
Air
Temperature
Sensor
Test
12

Manifold Absolute Pressure (MAP)
Sensor
Test
. 12

Oxygen
Sensor
Tests
17
Powertrain Control Module (PCM)
............
14

Spark
Plug Secondary Cables
16

Spark
Plugs
............................
14

Throttle
Position
Sensor
Test
17

(2) Connect
the
negative
(-)
voltmeter lead into
the

ground wire.
For
wire identification, refer
to
Group
8W, Wiring Diagrams.
(3)
Set the
voltmeter
to the 15
Volt
DC
scale. (4) Remove distributor
cap
from distributor
(two

screws). Rotate (crank)
the
engine until
the
distribu­
tor rotor
is
pointed towards
the
rear
of
vehicle.
The

movable pulse ring should
now be
within
the
sensor
pickup.
(5) Turn ignition
key to ON
position. Voltmeter
should read approximately
5.0
volts.
(6)
If
voltage
is not
present, check
the
voltmeter
leads
for a
good connection.
(7)
If
voltage
is
still
not
present, check
for
voltage
at
the
supply wire.
For
wire identification, refer
to

Group
8W,
Wiring Diagrams.
(8)
If
voltage
is not
present
at
supply wire, check
for voltage
at
pin-7
of
powertrain control module (PCM) 60-way connector. Leave
the PCM
connector
connected
for
this test. (9)
If
voltage
is
still
not
present, perform vehicle
test using
the DRB II
diagnostic scan tool. (10)
If
voltage
is
present
at
pin-7,
but not at the

supply wire: (a) Check continuity between
the
supply wire.
This
is
checked between
the
distributor connector and pin-7
at the PCM. If
continuity
is not
present,
repair
the
harness
as
necessary. (b) Check
for
continuity between
the
camshaft
position sensor output wire
and
pin-44
at the PCM.
If continuity
is not
present, repair
the
harness
as
necessary. (c) Check
for
continuity between
the
ground cir­
cuit wire
at the
distributor connector
and
ground.
If continuity
is not
present, repair
the
harness
as
necessary. (11) While observing
the
voltmeter, crank
the en­

gine with ignition switch.
The
voltmeter needle should fluctuate between
0 and 5
volts while
the en­

gine
is
cranking. This verifies that
the
camshaft
po­
sition sensor
in the
distributor
is
operating properly
and
a
sync pulse signal
is
being generated.

•

IGNITION
SYSTEMS
80 - 9

Fig.
4 Cap Inspection—internal—Typical
INSUFFICIENT
SPRING

TENSION

CORRODED
EVIDENCE
OF
PHYSICAL

CONTACT
WITH
CAP
J908D-48

Fig.
5 Rotor Inspection—Typical
Also refer to the appropriate Powertrain Diagnostics
Procedures manual. To test the coil only, refer to the
following:
The ignition coil (Figs. 6 or 7) is designed to oper­
ate without an external ballast resistor.
Fig.
6 Ignition Coil-3.9U5.2U5.9L
LDC-Gas
Engine

Fig.
7 Ignition Coil—5.9L
HDC-Gas
Engine
Inspect the ignition coil for arcing. Test the coil ac­
cording to coil tester manufacturer's instructions.
Test the coil primary and secondary resistance. Re­
place any coil that does not meet specifications. Refer
to the Ignition Coil Resistance chart.
If the ignition coil is being replaced, the secondary
spark plug cable must also be checked. Replace cable
if it has been burned or damaged.

IGNITION
COIL RESISTANCE

PRIMARY RESISTANCE SECONDARY RESISTANCE

COIL
(MANUFACTURER)
2!-27°C (70-80°F)
21-27°C
(70-80°F)

Diamond
0.97 - 1.18
Ohms
11,300-
15,300
Ohms

Toyodenso
0.95- 1.20
Ohms
11,300-
13,300
Ohms
J918D-2

8D
- 10
IGNITION
SYSTEMS

• Arcing at the tower will carbonize the cable boot,
which if it is connected to a new ignition coil, will cause the coil to fail. If the secondary coil cable shows any signs of dam­

age,
it should be replaced with a new cable and new
terminal. Carbon tracking on the old cable can cause
arcing and the failure of a new ignition coil.

ENGINE
COOLANT
TEMPERATURE
SENSOR
TEST
To perform a complete test of this sensor and its
circuitry, refer to the DRB II diagnostic scan tool.
Also refer to the appropriate Powertrain Diagnostics
Procedures manual. To test the sensor only, refer to
the following: The sensor is located in a water passage of the in­
take manifold next to the thermostat housing (Fig.
8).
(1) Disconnect wire harness connector from sensor
(Fig. 8). On engines with air conditioning, do not pull
directly on wiring harness. Fabricate an L-shaped
hook tool from a coat hanger (approximately eight inches long). Place the hook part of tool under the
connector for removal. The connector is snapped onto
the sensor. It is not equipped with a lock type tab.
COOLANT

TEMPERATURE
SENSOR
SENSOR RESISTANCE (OHMSJ
V

J9314-78

Fig. 8 Coolant Temperature Sensor—Typical (2) Test the resistance of the sensor with a high in­
put impedance (digital) volt-ohmmeter. The resis­ tance should be less than 1340 ohms at normal
engine operating idle temperature. For resistance
values, refer to the Sensor Resistance chart. Replace
the sensor if it is not within the range of resistance specified in the chart.
(3) Test continuity of the wire harness. This is
done between powertrain control module (PCM) wire
harness connector terminal-2 and the sensor connec­
tor terminal. Also check continuity between wire harness terminal-4 to the sensor connector terminal. Repair the wire harness if an open circuit is indi­
cated.
TEMPERATURE

RESISTANCE
(OHMS)

C
F
MIN
MAX

-40 -40 291,490 381,710
-20
-4
85,850
108,390
-10 14
49,250 61,430

0
32 29,330
35,990
10 50 17,990 21,810
20 68 11,370 13,610

25
77 9,120 10,880
30 86
7,370

8,750

40 104

4,900
5,750

50 122
3,330 3,880

60 140 2,310

2,670

70 158
1,630 1,870

80 176
1,170 1,340

90 194
860
970
100 212 640
720
110 230 480 540
120 248 370 410

J928D-4

IGNITION
SECONDARY
CIRCUIT
DIAGNOSIS

CHECKING FOR SPARK

CAUTION:
When
disconnecting a
high
voltage
cable

from
a spark
plug
or
from
the
distributor
cap,
twist
the rubber
boot
slightly
(1/2
turn)
to
break
it
loose.
Grasp
the
boot
(not the cable) and
pull
it off
with
a

steady,
even force.

(1) Disconnect the ignition coil secondary cable
from center tower of the distributor cap. Hold the ca­
ble terminal approximately 12 mm (1/2 in.) from a good engine ground (Fig. 9).
CHECK
HERE

FOR
SPARK
IGNITION

COIL
918D-18

Fig. 9 Checking for Spark—Typical

*
(1) Unplug the ignition coil harness connector at
the coil (Figs. 10 or 11).

Fig.
10
Coil
Harness
Connector—3.9/5.2L/5.9L
LDC-Gas
Engine

(2) Connect a set of small jumper wires (18 gauge
or smaller) between the ignition coil and coil electri­
cal connector (Fig. 12).
IGNITION
SYSTEMS
80 - 11

Fig.
11
Coil
Harness
Connector—5.9L
HDC-Gas
Engine

IGNITION
COIL COIL CONNECTOR

J928D-13

Fig.
12
Coil
Terminals—Typical (3) Determine that sufficient battery voltage (12.4
volts) is present for the starting and ignition sys­

tems.

(4) Crank the engine for 5 seconds while monitor­
ing the voltage at the coil positive terminal (Fig. 12):
• If the voltage remains near zero during the entire
period of cranking, refer to On-Board Diagnostics in Group 14, Fuel Systems. Check the powertrain con­
trol module and auto shut down relay.
• If voltage is at near battery voltage and drops to
zero after 1-2 seconds of cranking, check the power-
train control module circuit. Refer to On-Board Diag­ nostics in Group 14, Fuel Systems.
• If voltage remains at near battery voltage during
the entire 5 seconds, turn the key off. Remove the 60-way connector (Fig. 13) from the powertrain con­
trol module (PCM). Check 60-way connector for any spread terminals.
(5) Remove test lead from the coil positive termi­

nal.
Connect an 18 gauge jumper wire between the
battery positive terminal and the coil positive termi­
nal.
WARNING: BE VERY CAREFUL WHEN THE ENGINE

IS
CRANKING.
DO NOT PUT
YOUR HANDS NEAR
THE PULLEYS, BELTS
OR THE FAN. DO NOT
WEAR LOOSE
FITTING
CLOTHING.

(2) Rotate (crank) the engine with the starter mo­
tor and observe the cable terminal for a steady arc. If steady arcing does not occur, inspect the secondary
coil cable. Refer to Spark Plug Cables in this group.
Also inspect the distributor cap and rotor for cracks
or burn marks. Repair as necessary. If steady arcing occurs, connect ignition coil cable to the distributor
cap.

(3) Remove a cable from one spark plug.
(4) Using insulated pliers, hold the cable terminal
approximately 12 mm (1/2 in.) from the engine cylin­
der head or block while rotating the engine with the starter motor. Observe the spark plug cable terminal
for an arc. If steady arcing occurs, it can be expected
that the ignition secondary system is" operating cor­ rectly. If steady arcing occurs at the spark plug ca­

bles,
but the engine will not start, connect the DRB II diagnostic scan tool. Refer to the Powertrain Diag­
nostic Procedures service manual.

FAILURE
TO START TEST To prevent unnecessary diagnostic time and wrong
test results, the previous Checking For Spark test should be performed prior to this test.

WARNING: SET PARKING BRAKE
OR
BLOCK
THE
DRIVE WHEELS BEFORE PROCEEDING
WITH
THIS
TEST.

8D
- 12
IGNITION
SYSTEMS

•

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CONNECTOR

TERMINAL
SIDE
SHOWN
J908D-42
Fig. 13 PCM 60-Way Connector
(6) Make the special jumper shown in Figure 14.
Using the jumper, momentarily ground terminal-19
of the 60-way connector. A spark should be generated at the coil cable when the ground is removed.
CAPACITOR

GROUND
THIS
CLIP
CONNECT
THIS-

ALLIGATOR
CLIP

MOMENTARILY
GROUND
THIS
CLIP
TO
COIL^
NEGATIVE

ALLIGATOR
CLIP
PR1003

Fig. 14 Special Jumper Ground-to-Coil Negative Terminal (7) If spark is generated, replace the powertrain
control module (PCM).
(8) If spark is not seen, use the special jumper to
ground the coil negative terminal directly. (9) If spark is produced, repair wiring harness for
an open condition. (10) If spark is not produced, replace the ignition
coil.

IGNITION TIMING
Base (Initial) ignition timing Is NOT adjustable
on any engine. Do not attempt to adjust Ignition
timing by rotating the distributor. All ignition timing functions are controlled by the
powertrain control module (PCM). Refer to On-Board Diagnostics in the Multi-Port Fuel Injection—Gen­
eral Diagnosis section of Group 14, Fuel Systems for
more information. Also refer to the appropriate Pow­ ertrain Diagnostics Procedures service manual for
operation of the DRB II Scan Tool.

INTAKE
MANIFOLD
CHARGE
AIR
TEMPERATURE

SENSOR
TEST
To perform a complete test of this sensor and its
circuitry, refer to the DRB II diagnostic scan tool.
Also refer to the appropriate Powertrain Diagnostics Procedures manual. To test the sensor only, refer to
the following: (1) Disconnect the wire harness connector from the
sensor (Figs. 15 or 16).
THROTTLE
^

BODY
^

BRACKET
SUPPORT BRACKET
/

CHARGE
AIR

TEMPERATURE
SENSOR

Fig. 15 Sensor Location--3.9L Engine—Typical
INTAKE
MANIFOLD
AIR
TEMPERATURE

W
SENSOR

J9314-162

Fig. 16
Sensor
Location—5.2U5.9L
Engines—Typical
(2) Test the resistance of the sensor with a input
impedance (digital) volt-ohmmeter. Do not remove
the sensor from the engine for testing. For resistance
values, refer to the Sensor Resistance chart. Replace
the sensor if it is not within the range of resistance specified in the chart.
(3) Test the resistance of the wire harness. This is
done between the powertrain control module (PCM)
wire harness connector terminal-2 and the sensor connector terminal. Also check continuity between
terminal-4 to the sensor connector terminal. Repair
the wire harness as necessary if the resistance is greater than 1 ohm.
For removal and installation of this component, re­
fer to the Component Removal/Installation section of
this group.

MANIFOLD
ABSOLUTE PRESSURE
(MAP)
SENSOR
TEST
To perform a complete test of MAP sensor (Fig. 17)
and its circuitry, refer to DRB II tester and appropri-

8D
- 16
IGNITION
SYSTEMS

• other operating conditions are causing engine over­
heating. (The heat range rating refers to the operat­
ing temperature of a particular type spark plug.
Spark plugs are designed to operate within specific
temperature ranges. This depends upon the thickness and length of the center electrodes porcelain insula­
tor.)

GROUND

ELECTRODE
CENTER

ELECTRODE

DISSOLVED

J908D-14 Fig. 26 Preignition Damage

SPARK
PLUG
OVERHEATING
Overheating is indicated by a white or gray center
electrode insulator that also appears blistered (Fig.
27).
The increase in electrode gap will be consider­
ably in excess of 0.001 inch per 1000 miles of opera­
tion. This suggests that a plug with a cooler heat
range rating should be used. Over advanced ignition
timing, detonation and cooling system malfunctions can also cause spark plug overheating.

BLISTERED

WHITE
OR
J908D-16
Fig. 27 Spark Plug Overheating

SPARK
PLUG
SECONDARY
CABLES
Spark plug heat shields are pressed into the cylin­
der head to surround each spark plug cable boot and spark plug (Fig. 28). These shields protect the spark
plug boots from damage (due to intense engine heat
generated by the exhaust manifolds) and should not be removed. After the spark plug cable has been in­
stalled, the lip of the cable boot should have a small
air gap to the top of the heat shield (Fig. 28).

Fig.
28 Heat
Shields
TESTING

Spark plug cables are sometimes referred to as sec­
ondary ignition cables or secondary wires. The cables
transfer electrical current from the distributor to in­ dividual spark plugs at each cylinder. The spark plug
cables are of nonmetallic construction and have a
built in resistance. The cables provide suppression of radio frequency emissions from the ignition system.
Check the high-tension cable connections for good
contact at the ignition coil, distributor cap towers and spark plugs. Terminals should be fully seated.
The terminals and spark plug covers should be in good condition. Terminals should fit tightly to the ig­
nition coil, distributor cap and spark plugs. The spark plug cover (boot) of the cable should fit tight
around the spark plug insulator. Loose cable connec­
tions can cause corrosion and increase resistance, re­ sulting in shorter cable service life. Clean the high tension cables with a cloth moist­
ened with a nonflammable solvent and wipe dry.
Check for brittle or cracked insulation. When testing secondary cables for damage with an
oscilloscope, follow the instructions of the equipment
manufacturer. If an oscilloscope is not available, spark plug cables
may be tested as follows:

CAUTION:
Do not leave any one
spark
plug
cable

disconnected
for
longer
than
necessary
during test­
ing.
This
may
cause
possible
heat
damage
to the
catalytic converter. Total test
time
must
not exceed
ten
minutes.

With the engine not running, connect one end of a
test probe to a good ground. Start the engine and run the other end of the test probe along the entire length of all spark plug cables. If cables are cracked