2002 DODGE RAM ignition

to service. Refer toCharging Systemin the index of
this service manual for the charging system diagnos-
tic procedures.
(1) Position the generator cartridge fuse onto the
two B(+) terminal stud bus bars within the PDC.
(2) Install and tighten the two screws that secure
the generator cartridge fuse to the two B(+) terminal
stud bus bars within the PDC. Tighten the screws to
3.4 N´m (30 in. lbs.).Be certain that both screws
are tightened to the proper torque value.
(3) Install and latch the cover onto the PDC.
(4) Reconnect the battery negative cable.
IOD FUSE
DESCRIPTION
All vehicles are equipped with an Ignition-Off
Draw (IOD) fuse (Fig. 3) that is disconnected within
the Junction Block when the vehicle is shipped from
the factory. Dealer personnel are to reconnect the
IOD fuse in the junction block as part of the prepa-
ration procedures performed just prior to new vehicle
delivery.
The left end of the instrument panel cover has a
snap-fit fuse access panel that can be removed to pro-
vide service access to the fuses in the junction block.
A finger recess is molded into the access panel for
easy removal. An adhesive-backed fuse layout map issecured to the instrument panel side of the access
panel to ensure proper fuse identification. The IOD
fuse is a 10 ampere mini blade-type fuse. The fuse is
secured within a black molded plastic fuse holder
and puller unit that serves both as a tool for discon-
necting and reconnecting the fuse in its junction
block cavity, and as a fuse holder that conveniently
stores the fuse in the same junction block cavity after
it has been disconnected.
CIRCUITS INCLUDED WITH IOD FUSE
²Cargo Lamp
²CHMSL
²Diagnostic Connector
²Dome Lamp
²Glove Box Lamp
²Map/Reading Lamps
²Power Mirrors
²Radio
²Under Hood Lamp
OPERATION
The term ignition-off draw identifies a normal con-
dition where power is being drained from the battery
with the ignition switch in the Off position. The IOD
fuse feeds the memory and sleep mode functions for
some of the electronic modules in the vehicle as well
as various other accessories that require battery cur-
rent when the ignition switch is in the Off position,
including the clock. The only reason the IOD fuse is
disconnected is to reduce the normal IOD of the vehi-
cle electrical system during new vehicle transporta-
tion and pre-delivery storage to reduce battery
depletion, while still allowing vehicle operation so
that the vehicle can be loaded, unloaded and moved
as needed by both vehicle transportation company
and dealer personnel.
The IOD fuse is disconnected from JB fuse cavity
12 when the vehicle is shipped from the assembly
plant. Dealer personnel must reconnect the IOD fuse
when the vehicle is being prepared for delivery in
order to restore full electrical system operation. Once
the vehicle is prepared for delivery, the IOD function
of this fuse becomes transparent and the fuse that
has been assigned the IOD designation becomes only
another Fused B(+) circuit fuse. The IOD fuse serves
no useful purpose to the dealer technician in the ser-
vice or diagnosis of any vehicle system or condition,
other than the same purpose as that of any other
standard circuit protection device.
The IOD fuse can be used by the vehicle owner as
a convenient means of reducing battery depletion
when a vehicle is to be stored for periods not to
exceed about thirty days. However, it must be
remembered that disconnecting the IOD fuse will not
eliminate IOD, but only reduce this normal condition.
Fig. 3 Ignition-Off Draw Fuse
1 - JUNCTION BLOCK
2 - IGNITION-OFF DRAW FUSE AND HOLDER
3 - LEFT INSTRUMENT PANEL END BRACKET
BR/BE8W-97 POWER DISTRIBUTION 8W - 97 - 5
GENERATOR CARTRIDGE FUSE (Continued)

If a vehicle will be stored for more than about thirty
days, the battery negative cable should be discon-
nected to eliminate normal IOD; and, the battery
should be tested and recharged at regular intervals
during the vehicle storage period to prevent the bat-
tery from becoming discharged or damaged. Refer to
theBatterysection of the service manual for the
location of additional service information covering
the battery.
REMOVAL
The Ignition-Off Draw (IOD) fuse is disconnected
from Junction Block (JB) fuse cavity 12 when the
vehicle is shipped from the assembly plant. Dealer
personnel must reconnect the IOD fuse when the
vehicle is being prepared for delivery in order to
restore full electrical system operation.
(1) Turn the ignition switch to the Off position.
(2) Remove the fuse access panel by unsnapping it
from the left outboard end of the instrument panel.
(3) Grasp the upper and lower tabs of the IOD
fuse holder unit in fuse cavity 12 (Fig. 4) of the JB
between the thumb and forefinger and pull the unit
firmly outward.
(4) Install the fuse access panel by snapping it
onto the left outboard end of the instrument panel.
INSTALLATION
The Ignition-Off Draw (IOD) fuse is disconnected
from Junction Block (JB) fuse cavity 12 when the
vehicle is shipped from the assembly plant. Dealer
personnel must reconnect the IOD fuse when the
vehicle is being prepared for delivery in order to
restore full electrical system operation.
(1) Turn the ignition switch to the Off position.
(2) To install the IOD fuse, use a thumb to press
the IOD fuse holder unit in fuse cavity 12 firmly into
the JB.
(3) Install the fuse access panel by snapping it
onto the left outboard end of the instrument panel.
JUNCTION BLOCK
DESCRIPTION
An electrical Junction Block (JB) is concealed
behind the left outboard end of the instrument panel
cover (Fig. 5). The JB combines the functions previ-
ously provided by a separate fuseblock module and
relay center, serves to simplify and centralize numer-
ous electrical components, and to distribute electrical
current to many of the accessory systems in the vehi-
cle. It also eliminates the need for numerous splice
connections and serves in place of a bulkhead connec-
Fig. 4 Ignition-Off Draw Fuse
1 - JUNCTION BLOCK
2 - IGNITION-OFF DRAW FUSE AND HOLDER
3 - LEFT INSTRUMENT PANEL END BRACKETFig. 5 Junction Block Location
1 - JUNCTION BLOCK
2 - FUSE ACCESS PANEL
8W - 97 - 6 8W-97 POWER DISTRIBUTIONBR/BE
IOD FUSE (Continued)

contained within a small, rectangular, molded plastic
housing and is connected to all of the required inputs
and outputs by five integral male spade-type termi-
nals that extend from the bottom of the relay base.
Relays cannot be adjusted or repaired and, if faulty
or damaged, the unit must be replaced.
OPERATION
A micro-relay is an electromechanical switch that
uses a low current input from one source to control a
high current output to another device. The movable
common feed contact point is held against the fixed
normally closed contact point by spring pressure.
When the relay coil is energized, an electromagnetic
field is produced by the coil windings. This electro-
magnetic field draws the movable relay contact point
away from the fixed normally closed contact point,
and holds it against the fixed normally open contact
point. When the relay coil is de-energized, spring
pressure returns the movable contact point back
against the fixed normally closed contact point. A
resistor is connected in parallel with the relay coil in
the relay, and helps to dissipate voltage spikes and
electromagnetic interference that can be generated as
the electromagnetic field of the relay coil collapses.
DIAGNOSIS AND TESTING - MICRO-RELAY
(1) Remove the relay from its mounting location.
(2) A relay in the de-energized position should
have continuity between terminals 87A and 30, and
no continuity between terminals 87 and 30. If OK, go
to Step 3. If not OK, replace the faulty relay.
(3) Resistance between terminals 85 and 86 (elec-
tromagnet) should be 67.5 - 82.5 ohms. If OK, go to
Step 4. If not OK, replace the faulty relay.
(4) Connect a battery to terminals 85 and 86.
There should now be continuity between terminals
30 and 87, and no continuity between terminals 87A
and 30. If OK, reinstall the relay and use a DRBIIIt
scan tool to perform further testing. Refer to the
appropriate diagnostic information.
Refer to the appropriate wiring information. The
wiring information includes wiring diagrams, proper
wire and connector repair procedures, details of wire
harness routing and retention, connector pin-out
information and location views for the various wire
harness connectors, splices and grounds.
REMOVAL
(1) Remove the relay by grasping it firmly and
pulling it straight out from its receptacle.
INSTALLATION
(1) Align the micro-relay terminals with the termi-
nal cavities in the receptacle.(2) Push firmly and evenly on the top of the relay
until the terminals are fully seated in the terminal
cavities in the receptacle.
RELAY
DESCRIPTION
A relay is an electromechanical device that
switches fused battery current to a electrical compo-
nent when the ignition switch is turned to the Acces-
sory or Run positions, or when controlled by a
electronic module. The relays are located in the junc-
tion block or power distribution center (Fig. 17).
The relay is a International Standards Organiza-
tion (ISO) relay. Relays conforming to the ISO speci-
fications have common physical dimensions, current
capacities, terminal patterns, and terminal functions.
A relay cannot be repaired or adjusted and, if
faulty or damaged, it must be replaced.
OPERATION
The ISO relay consists of an electromagnetic coil, a
resistor and three (two fixed and one movable) elec-
trical contacts. The movable (common feed) relay con-
tact is held against one of the fixed contacts
(normally closed) by spring pressure. When the elec-
tromagnetic coil is energized, it draws the movable
contact away from the normally closed fixed contact,
and holds it against the other (normally open) fixed
contact.
When the electromagnetic coil is de-energized,
spring pressure returns the movable contact to the
normally closed position. The resistor is connected in
parallel with the electromagnetic coil in the relay,
and helps to dissipate voltage spikes that are pro-
duced when the coil is de-energized.
Fig. 17 TYPE 1 RELAY
8W - 97 - 14 8W-97 POWER DISTRIBUTIONBR/BE
MICRO-RELAY (Continued)

DIAGNOSIS AND TESTING - RELAY
The relays are located in the junction block or
power distribution center. For complete circuit dia-
grams, refer toWiring Diagrams.
(1) Remove the relay from its mounting location.
(2) A relay in the de-energized position should
have continuity between terminals 87A and 30, and
no continuity between terminals 87 and 30. If OK, go
to Step 3. If not OK, replace the faulty relay.
(3) Resistance between terminals 85 and 86 (elec-
tromagnet) should be 60.7 - 80.3 ohms. If OK, go to
Step 4. If not OK, replace the faulty relay.
(4) Connect a battery to terminals 85 and 86.
There should now be continuity between terminals
30 and 87, and no continuity between terminals 87A
and 30. If OK, perform the Relay Circuit Test that
follows. If not OK, replace the faulty relay.
DIAGNOSIS AND TESTING - RELAY CIRCUIT TEST
(1) The relay common feed terminal cavity (30) of
the junction block or power distribution center is con-
nected to battery voltage and should be hot at all
times. Check for battery voltage at the fused B(+) cir-
cuit cavity in the junction block receptacle for the
relay. If OK, go to Step 2. If not OK, repair the fused
B(+) circuit to the Power Distribution Center (PDC)
fuse as required.
(2) The relay normally closed terminal (87A) is
connected to terminal 30 in the de-energized position,
but is not used for this application. Go to Step 3.
(3) The relay normally open terminal (87) is con-
nected to the common feed terminal (30) in the ener-
gized position. This terminal supplies battery voltage
to the fused B(+) fuse in the junction block that feedsthe accessory when the relay is energized by the igni-
tion switch. There should be continuity between the
junction block cavity for relay terminal 87 and the
fused B(+) fuse in the junction block at all times. If
OK, go to Step 4. If not OK, repair the open fused
B(+) circuit to the junction block fuse as required.
(4) The coil ground terminal (85) is connected to
the electromagnet in the relay. It receives battery
feed to energize the relay when the ignition switch is
in the Accessory or Run positions. Turn the ignition
switch to the On position. Check for battery voltage
at the fused ignition switch output (acc/run) circuit
cavity for relay terminal 85 in the junction block
receptacle for the relay. If OK, go to Step 5. If not
OK, repair the open fused ignition switch output
(acc/run) circuit to the ignition switch as required.
(5) The coil battery terminal (86) is connected to
the electromagnet in the relay. The junction block
cavity for this terminal should have continuity to
ground at all times. If not OK, repair the open
ground circuit to ground as required.
REMOVAL
(1) Remove the relay by grasping it firmly and
pulling it straight out from its receptacle.
INSTALLATION
(1) Position the relay to the proper receptacle.
(2) Align the relay terminals with the terminal
cavities in the receptacle.
(3) Push firmly and evenly on the top of the relay
until the terminals are fully seated in the terminal
cavities in the receptacle.
BR/BE8W-97 POWER DISTRIBUTION 8W - 97 - 15
RELAY (Continued)

DIAGNOSIS AND TESTINGÐENGINE
DIAGNOSIS - PERFORMANCE
PERFORMANCE DIAGNOSIS CHARTÐGASOLINE ENGINES
CONDITION POSSIBLE CAUSES CORRECTION
ENGINE WILL NOT CRANK 1. Weak or dead battery 1. Charge/Replace Battery. (Refer to
8 - ELECTRICAL/BATTERY
SYSTEM/BATTERY - STANDARD
PROCEDURE). Check charging
system. (Refer to 8 - ELECTRICAL/
CHARGING - DIAGNOSIS AND
TESTING).
2. Corroded or loose battery
connections2. Clean/tighten suspect battery/
starter connections
3. Faulty starter or related circuit(s) 3. Check starting system. (Refer to
8 - ELECTRICAL/STARTING -
DIAGNOSIS AND TESTING)
4. Seized accessory drive
component4. Remove accessory drive belt and
attempt to start engine. If engine
starts, repair/replace seized
component.
5. Engine internal mechanical
failure or hydro-static lock5. Refer to (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
ENGINE CRANKS BUT WILL NOT
START1. No spark 1. Check for spark. (Refer to 8 -
ELECTRICAL/IGNITION CONTROL
- DESCRIPTION)
2. No fuel 2. Perform fuel pressure test, and if
necessary, inspect fuel injector(s)
and driver circuits. (Refer to 14 -
FUEL SYSTEM/FUEL DELIVERY/
FUEL PUMP - DIAGNOSIS AND
TESTING).
3. Low or no engine compression 3. Perform cylinder compression
pressure test. (Refer to 9 - ENGINE
- DIAGNOSIS AND TESTING).
ENGINE LOSS OF POWER 1. Worn or burned distributor rotor 1. Install new distributor rotor
2. Worn distributor shaft 2. Remove and repair distributor
(Refer to 8 - ELECTRICAL/
IGNITION CONTROL/
DISTRIBUTOR - REMOVAL).
3. Worn or incorrect gapped spark
plugs3. Clean plugs and set gap. (Refer
to 8 - ELECTRICAL/IGNITION
CONTROL/SPARK PLUG -
CLEANING).
4. Dirt or water in fuel system 4. Clean system and replace fuel
filter
5. Faulty fuel pump 5. Install new fuel pump
6. Incorrect valve timing 6. Correct valve timing
9 - 4 ENGINE 5.9LBR/BE
ENGINE 5.9L (Continued)

CONDITION POSSIBLE CAUSES CORRECTION
7. Blown cylinder head gasket 7. Install new cylinder head gasket
8. Low compression 8. Test cylinder compression (Refer
to 9 - ENGINE - DIAGNOSIS AND
TESTING).
9. Burned, warped, or pitted valves 9. Install/Reface valves as
necessary
10. Plugged or restricted exhaust
system10. Install new parts as necessary
11. Faulty ignition cables 11. Replace any cracked or shorted
cables
12. Faulty ignition coil 12. Test and replace, as necessary
(Refer to 8 - ELECTRICAL/
IGNITION CONTROL/IGNITION
COIL - REMOVAL).
ENGINE STALLS OR ROUGH IDLE 1. Carbon build-up on throttle plate 1. Remove throttle body and
de-carbon. (Refer to 14 - FUEL
SYSTEM/FUEL INJECTION/
THROTTLE BODY - REMOVAL).
2. Engine idle speed too low 2. Check Idle Air Control circuit.
(Refer to 14 - FUEL SYSTEM/FUEL
INJECTION/IDLE AIR CONTROL
MOTOR - DESCRIPTION)
3. Worn or incorrectly gapped spark
plugs3. Replace or clean and re-gap
spark plugs (Refer to 8 -
ELECTRICAL/IGNITION CONTROL/
SPARK PLUG - CLEANING)
4. Worn or burned distributor rotor 4. Install new distributor rotor
5. Spark plug cables defective or
crossed5. Check for correct firing order or
replace spark plug cables. (Refer to
8 - ELECTRICAL/IGNITION
CONTROL/SPARK PLUG CABLE -
DIAGNOSIS AND TESTING)
6. Faulty coil 6. Test and replace, if necessary
(Refer to 8 - ELECTRICAL/
IGNITION CONTROL/IGNITION
COIL - REMOVAL)
7. Intake manifold vacuum leak 7. Inspect intake manifold gasket
and vacuum hoses (Refer to 9 -
ENGINE/MANIFOLDS/INTAKE
MANIFOLD - DIAGNOSIS AND
TESTING).
ENGINE MISSES ON
ACCELERATION1. Worn or incorrectly gapped spark
plugs1. Replace spark plugs or clean and
set gap. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/SPARK PLUG
- CLEANING)
2. Spark plug cables defective or
crossed2. Replace or rewire secondary
ignition cables. (Refer to 8 -
ELECTRICAL/IGNITION CONTROL/
SPARK PLUG CABLE - REMOVAL)
BR/BEENGINE 5.9L 9 - 5
ENGINE 5.9L (Continued)

CONDITION POSSIBLE CAUSES CORRECTION
3. Dirt in fuel system 3. Clean fuel system
4. Burned, warped or pitted valves 4. Install new valves
5. Faulty coil 5. Test and replace as necessary
(Refer to 8 - ELECTRICAL/
IGNITION CONTROL/IGNITION
COIL - REMOVAL)
DIAGNOSIS AND TESTINGÐ ENGINE
DIAGNOSIS - MECHANICAL
ENGINE MECHANICAL DIAGNOSIS CHART
CONDITION POSSIBLE CAUSES CORRECTION
NOISY VALVES/LIFTERS 1. High or low oil level in crankcase 1. Check for correct oil level. Adjust
oil level by draining or adding as
needed
2. Thin or diluted oil 2. Change oil. (Refer to 9 -
ENGINE/LUBRICATION/OIL -
STANDARD PROCEDURE)
3. Low oil pressure 3. Check engine oil level. If ok,
Perform oil pressure test. (Refer to
9 - ENGINE/LUBRICATION -
DIAGNOSIS AND TESTING) for
engine oil pressure test/
specifications
4. Dirt in tappets/lash adjusters 4. Clean/replace hydraulic
tappets/lash adjusters
5. Bent push rod(s) 5. Install new push rods
6. Worn rocker arms 6. Inspect oil supply to rocker arms
and replace worn arms as needed
7. Worn tappets/lash adjusters 7. Install new hydraulic tappets/lash
adjusters
8. Worn valve guides 8. Inspect all valve guides and
replace as necessary
9. Excessive runout of valve seats
or valve faces9. Grind valves and seats
CONNECTING ROD NOISE 1. Insufficient oil supply 1. Check engine oil level.
2. Low oil pressure 2. Check engine oil level. If ok,
Perform oil pressure test. (Refer to
9 - ENGINE/LUBRICATION -
DIAGNOSIS AND TESTING) engine
oil pressure test/specifications
3. Thin or diluted oil 3. Change oil to correct viscosity.
(Refer to 9 - ENGINE/
LUBRICATION/OIL - STANDARD
PROCEDURE) for correct
procedure/engine oil specifications
9 - 6 ENGINE 5.9LBR/BE
ENGINE 5.9L (Continued)

CONDITION POSSIBLE CAUSES CORRECTION
OIL PUMPING AT RINGS; SPARK
PLUGS FOULING1. Worn or damaged rings. 1. Hone cylinder bores and replace
rings.
2. Carbon in oil ring slots. 2. Replace rings.
3. Incorrect ring size installed. 3. Replace rings.
4. Worn valve guides. 4. Ream guides and replace valves.
5. Leaking intake gasket. 5. Replace intake gaskets.
6. Leaking valve guide seals. 6. Replace valve guide seals.
DIAGNOSIS AND TESTINGÐCYLINDER
COMPRESSION PRESSURE
The results of a cylinder compression pressure test
can be utilized to diagnose several engine malfunc-
tions.
Ensure the battery is completely charged and the
engine starter motor is in good operating condition.
Otherwise, the indicated compression pressures may
not be valid for diagnosis purposes.
(1) Clean the spark plug recesses with compressed
air.
(2) Remove the spark plugs (Refer to 8 - ELEC-
TRICAL/IGNITION CONTROL/SPARK PLUG -
REMOVAL).
(3) Secure the throttle in the wide-open position.
(4) Disconnect the ignition coil.
(5) Insert a compression pressure gauge and rotate
the engine with the engine starter motor for three
revolutions.
(6) Record the compression pressure on the third
revolution. Continue the test for the remaining cylin-
ders.
(Refer to 9 - ENGINE - SPECIFICATIONS) for the
correct engine compression pressures.
DIAGNOSIS AND TESTING - CYLINDER
COMBUSTION PRESSURE LEAKAGE
The combustion pressure leakage test provides an
accurate means for determining engine condition.
Combustion pressure leakage testing will detect:
²Exhaust and intake valve leaks (improper seat-
ing)
²Leaks between adjacent cylinders or into water
jacket²Any causes for combustion/compression pressure
loss
WARNING: DO NOT REMOVE THE RADIATOR CAP
WITH THE SYSTEM HOT AND UNDER PRESSURE.
SERIOUS BURNS FROM HOT COOLANT CAN
OCCUR.
Check the coolant level and fill as required. DO
NOT install the radiator cap.
Start and operate the engine until it attains nor-
mal operating temperature, then turn OFF the
engine.
Remove the spark plugs.
Remove the oil filler cap.
Remove the air cleaner.
Calibrate the tester according to the manufactur-
er's instructions. The shop air source for testing
should maintain 483 kPa (70 psi) minimum, 1,379
kPa (200 psi) maximum and 552 kPa (80 psi) recom-
mended.
Perform the test procedure on each cylinder accord-
ing to the tester manufacturer's instructions. While
testing, listen for pressurized air escaping through
the throttle body, tailpipe or oil filler cap opening.
Check for bubbles in the radiator coolant.
All gauge pressure indications should be equal,
with no more than 25% leakage.
FOR EXAMPLE:At 552 kPa (80 psi) input pres-
sure, a minimum of 414 kPa (60 psi) should be main-
tained in the cylinder CYLINDER COMBUSTION
PRESSURE LEAKAGE DIAGNOSIS CHART .
BR/BEENGINE 5.9L 9 - 9
ENGINE 5.9L (Continued)