bulb DODGE RAM 1500 1998 2.G Repair Manual

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 75   8 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.
REMOVAL
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE SUPPLEMENTAL RESTRAINT
SYSTEM BEFORE ATTEMPTING ANY STEERING
WHEEL, STEERING COLUMN, DRIVER AIRBAG,
PASSENGER AIRBAG, SEAT BELT TENSIONER,
FRONT IMPACT SENSORS, SIDE CURTAIN AIRBAG,
OR INSTRUMENT PANEL COMPONENT DIAGNOSIS
OR SERVICE. DISCONNECT AND ISOLATE THE
BATTERY NEGATIVE (GROUND) CABLE, THEN
WAIT TWO MINUTES FOR THE SYSTEM CAPACI-
TOR TO DISCHARGE BEFORE PERFORMING FUR-
THER DIAGNOSIS OR SERVICE. THIS IS THE ONLY
SURE WAY TO DISABLE THE SUPPLEMENTAL
RESTRAINT SYSTEM. FAILURE TO TAKE THE
PROPER PRECAUTIONS COULD RESULT IN ACCI-
DENTAL AIRBAG DEPLOYMENT AND POSSIBLE
PERSONAL INJURY.
(1) Disconnect and isolate the battery negative
cable.(2) Remove the Power Distribution Center (PDC)
cover.
(3) Remove the park lamp relay by grasping it
firmly and pulling it straight out from the receptacle
in the PDC.
INSTALLATION
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE SUPPLEMENTAL RESTRAINT
SYSTEM BEFORE ATTEMPTING ANY STEERING
WHEEL, STEERING COLUMN, DRIVER AIRBAG,
PASSENGER AIRBAG, SEAT BELT TENSIONER,
FRONT IMPACT SENSORS, SIDE CURTAIN AIRBAG,
OR INSTRUMENT PANEL COMPONENT DIAGNOSIS
OR SERVICE. DISCONNECT AND ISOLATE THE
BATTERY NEGATIVE (GROUND) CABLE, THEN
WAIT TWO MINUTES FOR THE SYSTEM CAPACI-
TOR TO DISCHARGE BEFORE PERFORMING FUR-
THER DIAGNOSIS OR SERVICE. THIS IS THE ONLY
SURE WAY TO DISABLE THE SUPPLEMENTAL
RESTRAINT SYSTEM. FAILURE TO TAKE THE
PROPER PRECAUTIONS COULD RESULT IN ACCI-
DENTAL AIRBAG DEPLOYMENT AND POSSIBLE
PERSONAL INJURY.
(1) Position the park lamp relay to the proper
receptacle in the Power Distribution Center (PDC).
(2) Align the park lamp relay terminals with the
terminal cavities in the PDC.
(3) Press firmly and evenly on the top of the park
lamp relay until the terminals are fully seated in the
PDC.
(4) Install the PDC cover.
(5) Reconnect the battery negative cable.
PARK/TURN SIGNAL LAMP
REMOVAL
(1) Disconnect and isolate the negative battery
cable.
(2) Remove the headlamp unit.(Refer to 8 - ELEC-
TRICAL/LAMPS/LIGHTING - EXTERIOR/HEAD-
LAMP UNIT - REMOVAL).
(3) Remove the bulb socket from the headlamp
unit.
(4) Release the front park/turn signal bulb locking
tabs and remove the bulb from the socket (Fig. 19).
INSTALLATION
(1) Install the front park/turn signal bulb into the
bulb socket.
(2) Install the bulb socket into the headlamp unit.
(3) Install the headlamp unit (Refer to 8 - ELEC-
TRICAL/LAMPS/LIGHTING - EXTERIOR/HEAD-
LAMP UNIT - INSTALLATION).
Fig. 18 ISO Micro Relay
30 - COMMON FEED
85 - COIL GROUND
86 - COIL BATTERY
87 - NORMALLY OPEN
87A - NORMALLY CLOSED
DRLAMPS/LIGHTING - EXTERIOR 8L - 21
PARK LAMP RELAY (Continued)

(4) Reconnect the negative battery cable.
TAIL LAMP
REMOVAL
REMOVAL - WITH CARGO BOX
(1) Disconnect and isolate the negative battery
cable.
(2) Remove the tail lamp unit (Refer to 8 - ELEC-
TRICAL/LAMPS/LIGHTING - EXTERIOR/TAIL
LAMP UNIT - REMOVAL).
(3) Remove the lamp back plate from the tail lamp
unit.
(4) Release the tail lamp bulb locking tabs and
remove the bulb from the back plate.
REMOVAL - WITHOUT CARGO BOX
(1) Disconnect and isolate the negative battery
cable.
(2) Remove the four screws that secure the tail
lamp lens to the tail lamp housing (Fig. 20).
(3) Separate the tail lamp lens from the tail lamp
housing.
(4) Push the tail lamp bulb inward and rotate it
counter-clockwise.
(5) Remove the tail lamp bulb from the tail lamp
socket.
INSTALLATION
INSTALLATION - WITH CARGO BOX
(1) Install the tail lamp bulb into the lamp back
plate.
(2) Install the lamp back plate onto the tail lamp
unit.(3) Install the tail lamp unit (Refer to 8 - ELEC-
TRICAL/LAMPS/LIGHTING - EXTERIOR/TAIL
LAMP UNIT - INSTALLATION).
(4) Reconnect the negative battery cable.
INSTALLATION - WITHOUT CARGO BOX
(1) Install the tail lamp bulb into the tail lamp
socket by pushing inward and rotating it clockwise.
NOTE: Install the tail lamp lens with the clear por-
tion (back-up lens) at the top of the housing. Make
sure that the gasket is correctly in place and not
twisted or torn.
(2) Position the tail lamp lens and gasket onto the
tail lamp unit.
NOTE: Do not overtighten the tail lamp lens screws
or damage to the tail lamp lens may result.
(3) Install the four screws that secure the tail
lamp lens to the tail lamp unit. Tighten the screws
securely.
(4) Reconnect the negative battery cable.
TAIL LAMP UNIT
REMOVAL
REMOVAL - WITH CARGO BOX
(1) Disconnect and isolate the negative battery
cable.
(2) Lower the tailgate.
(3) Remove the two screws that secure the tail
lamp unit to the cargo box.
(4) Remove the tail lamp unit from the cargo box.
(5) Disconnect the body wire harness connector
from the lamp back plate connector (Fig. 21).
Fig. 19 Park Turn Signal Bulb
1 - BULB SOCKET
2 - BULB
Fig. 20 Tail Lamp Lens
8L - 22 LAMPS/LIGHTING - EXTERIORDR
PARK/TURN SIGNAL LAMP (Continued)

TRAILER TOW WIRING
DESCRIPTION
Vehicles equipped with an optional factory-in-
stalled trailer towing package have a rear body wire
harness that includes an integral trailer tow wiring
take out that connects to a heavy duty, sealed, 7-pin
trailer tow connector located in the rear bumper (Fig.
23). This harness includes an adapter harness that
adapts the 7-pin trailer tow connector to a standard,
light-duty, 4-pin trailer tow connector. Refer to the
appropriate wiring information.
TURN LAMP
REMOVAL
REMOVAL - WITH CARGO BOX
(1) Disconnect and isolate the negative battery
cable.
(2) Remove the tail lamp unit (Refer to 8 - ELEC-
TRICAL/LAMPS/LIGHTING - EXTERIOR/TAIL
LAMP UNIT - REMOVAL).
(3) Remove the lamp back plate from the tail lamp
unit.
(4) Release the turn signal bulb locking tabs and
remove the bulb from the back plate.
REMOVAL - WITHOUT CARGO BOX
(1) Disconnect and isolate the negative battery
cable.(2) Remove the four screws that secure the tail
lamp lens to the tail lamp housing (Fig. 24).
(3) Separate the tail lamp lens from the tail lamp
housing.
(4) Push the turn signal bulb inward and rotate it
counter-clockwise.
(5) Remove the turn signal bulb from the tail lamp
socket.
INSTALLATION
INSTALLATION - WITH CARGO BOX
(1) Install the turn signal bulb into the lamp back
plate.
(2) Install the lamp back plate onto the tail lamp
unit.
(3) Install the tail lamp unit (Refer to 8 - ELEC-
TRICAL/LAMPS/LIGHTING - EXTERIOR/TAIL
LAMP UNIT - INSTALLATION).
(4) Reconnect the negative battery cable.
INSTALLATION - WITHOUT CARGO BOX
(1) Install the turn signal bulb into the tail lamp
socket by pushing inward and rotating it clockwise.
NOTE: Install the tail lamp lens with the clear por-
tion (back-up lens) at the top of the housing. Make
sure that the gasket is correctly in place and not
twisted or torn.
(2) Position the tail lamp lens and gasket onto the
tail lamp unit.
NOTE: Do not overtighten the tail lamp lens screws
or damage to the tail lamp lens may result.
(3) Install the four screws that secure the tail
lamp lens to the tail lamp unit. Tighten the screws
securely.
(4) Reconnect the negative battery cable.
Fig. 23 Trailer Tow Wiring
1 - RETAINER CLIP (4)
2 - REAR BODY HARNESS (TRAILER TOW TAKE OUT)
3 - RETAINER CLIP (2)
4 - WIRE HARNESS CONNECTOR
Fig. 24 Tail Lamp Lens
8L - 24 LAMPS/LIGHTING - EXTERIORDR

UNDERHOOD LAMP
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Insert a small flat blade in the access slot
between the lamp base and lamp lens.
(3) Pry the lamp lens upward and remove the
lamp lens (Fig. 25).
(4) Depress the bulb terminal inward (Fig. 26) to
release the bulb.
INSTALLATION
(1) Engage the replacement bulb wire loop to the
terminal closest to the lamp base wire connector (Fig.
26).
(2) Depress the opposite terminal inward and
engage the remaining bulb wire loop.
(3) Position the lamp lens on the lamp base and
press into place (Fig. 25).
(4) Connect the battery negative cable.
UNDERHOOD LAMP UNIT
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Disconnect the wire harness connector from the
lamp.
(3) Remove lamp lens.
(4) Remove bulb.
(5) Remove screw attaching underhood lamp to the
inner hood panel (Fig. 27).
(6) Separate underhood lamp from vehicle.
INSTALLATION
(1) Install bulb.
(2) Install lamp lens.
(3) Position the underhood lamp on the hood inner
panel.
(4) Install the attaching screw through the lamp
and into the hood panel (Fig. 27). Tighten the screw
securely.
(5) Fold lamp housing over and firmly press onto
base to snap into place.
(6) Connect the wire harness connector to the
lamp.
(7) Connect the battery negative cable.
Fig. 25 Underhood Lamp Lens
1 - LAMP
2 - LAMP LENS
Fig. 26 Underhood Lamp Bulb
1 - BULB
2 - DEPRESS TERMINAL INWARD
3 - BULB WIRE LOOP
4 - LAMP BASE
Fig. 27 Underhood Lamp
1 - UNDER HOOD LAMP
2 - HOOD
3 - CONNECTOR
DRLAMPS/LIGHTING - EXTERIOR 8L - 25

LAMPS/LIGHTING - INTERIOR
TABLE OF CONTENTS
page page
DOME LAMP
DESCRIPTION.........................26
OPERATION...........................26
REMOVAL.............................26
INSTALLATION.........................26
DOOR AJAR SWITCH
DESCRIPTION.........................27
OPERATION...........................27GLOVE BOX LAMP/SWITCH
REMOVAL.............................27
INSTALLATION.........................28
READING LAMP
DESCRIPTION.........................28
OPERATION...........................28
REMOVAL.............................28
INSTALLATION.........................29
DOME LAMP
DESCRIPTION
The dome lamp is controlled by the instrument
cluster which provides power at all times, regardless
of the ignition switch position. The ground circuit for
the lamp is switched through the integral dome lamp
switch or through the door ajar switches via the
instrument cluster.
The dome lamp lens and bulb are available for ser-
vice replacement. If either of the lamp switch or bulb
holders is faulty or damaged, the dome lamp assem-
bly must be replaced.
For service of the dome lamp bulb, refer to the
appropriate wiring information.
OPERATION
The dome lamp is activated by the door ajar
switches via the instrument cluster. When all of the
doors are closed, the lamp can be activated by
depressing the lens. When any door is open, depress-
ing the lamp lense to activate the lamp switch will
not turn the lamps off.
The instrument cluster monitors the door ajar
switches. When a door is open the instrument cluster
grounds the low side drivers to turn on the lamp.
Upon closing all doors, the instrument cluster ini-
tiates a 30 second timer. If any of the doors are
opened during the ªtime outº cycle, the instrument
cluster will reset the timer until all doors are closed.
The instrument cluster will faid to off when the doors
are closed and the ignition is turned ON, the time
out expires or the power locks are activated.
REMOVAL
(1) Using a small flat blade, pry the left side (driv-
er's side) of the dome lamp lens downward from
dome lamp.(2) Allow the lens to hang down (Fig. 1), this will
disengage the right side of the lamp (passenger's
side) from the headliner.
(3) Pull the right side of the lamp down and slide
the lamp to the right (Fig. 2).
(4) Separate the lamp from the headliner.
(5) Disengage dome lamp wire connector from body
wire harness.
(6) Separate dome lamp from vehicle.
INSTALLATION
(1) Position dome lamp at headliner.
(2) Connect dome lamp wire connector to body
wire harness.
(3) Position the left side of the lamp in the head-
liner opening and slide lamp to the left (Fig. 1).
Fig. 1 Dome Lamp Lens
1 - HEADLINER
2 - CONNECTOR
3 - DOME LAMP
4 - LENS
5 - BULB
8L - 26 LAMPS/LIGHTING - INTERIORDR

INSTALLATION
(1) Reach through the glove box opening and
behind the glove box lamp and switch mounting
bracket to feed the instrument panel wire harness
connectors out through the hole in the glove box
lamp and switch housing mounting bracket.
(2) Position the glove box lamp and switch unit to
the instrument panel.
(3) Reconnect the instrument panel wire harness
connector to the connector receptacle on the back of
the glove box lamp and switch unit.
(4) Push the glove box lamp and switch unit into
the hole in the mounting bracket on the instrument
panel glove box opening upper reinforcement.
(5) Install the glove box onto the instrument panel.
(Refer to 23 - BODY/INSTRUMENT PANEL/GLOVE
BOX - INSTALLATION) for the procedures.
(6) Close the glove box.
(7) Reconnect the battery negative cable.
READING LAMP
DESCRIPTION
The overhead console in this vehicle is equipped
with two individual reading and courtesy lamps. The
lamp lenses are the only visible components of these
lamps. Each lamp has its own switch, bulb, reflector
and lens within the overhead console.
The overhead console reading and courtesy lamps
are controlled by the instrument cluster which pro-
vides power at all times, regardless of the ignition
switch position. The ground circuit for the lamps is
switched through the integral reading and courtesy
lamp switches or through the door ajar switches.
Each lamp is designed and aimed to provide illumi-
nation that will be directed only to that side of the
vehicle on which the lamp is located.
The reading and courtesy lamp lenses and bulbs
are available for service replacement. The reading
and courtesy lamp switches, bulb holders and wiring
are only available as part of the overhead console
wire harness. If either of the lamp switches or bulb
holders is faulty or damaged, the entire overhead
console wire harness assembly must be replaced.
For service of the reading and courtesy lamp bulbs,
refer to the appropriate wiring information.
OPERATION
All reading and courtesy lamps located in the over-
head console are activated by the door ajar switches
via the instrument cluster. When all of the doors are
closed, these lamps can be individually activated by
depressing the corresponding lens. When any door is
open, depressing the lamp lenses to activate the lamp
switches will not turn the lamps off.The instrument cluster monitors the door ajar
switches. When a door is open the instrument cluster
grounds the low side drivers to turn on the lamps.
Upon closing all doors, the instrument cluster ini-
tiates a 30 second timer. If any of the doors are
opened during the ªtime outº cycle, the instrument
cluster will reset the timer until all doors are closed.
The instrument cluster will faid to off when the doors
are closed and the ignition is turned ON, the time
out expires or the power locks are activated.
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Insert a long, narrow, flat-bladed tool between
the curved (outboard) edge of the reading and cour-
tesy lamp lens and the overhead console housing
(Fig. 4).
(3) Gently pry inward and downward against the
lens until the latch tab in the center of the outboard
edge of the reading and courtesy lamp lens is disen-
gaged from the overhead console housing.
(4) Pull firmly on the lens toward the outboard
side of the vehicle to disengage the two pivot tabs on
the inboard edge of the reading and courtesy lamp
lens are disengaged from the overhead console hous-
ing.
(5) Remove the reading and courtesy lamp lens
from the overhead console housing.
Fig. 4 Overhead Console Reading Lamp Bulb
Removal
1 - LENS
2 - FLAT BLADE
3 - CONSOLE
8L - 28 LAMPS/LIGHTING - INTERIORDR
GLOVE BOX LAMP/SWITCH (Continued)

into the passenger airbag door on the instrument
panel above the glove box (Fig. 2). Vehicles with the
airbag system can also be identified by the airbag
indicator, which will illuminate in the instrument
cluster for about six seconds as a bulb test each time
the ignition switch is turned to the On position. A
pyrotechnic-type seat belt tensioner is integral to the
front outboard seat belt retractors mounted on each
lower B-pillar of all models equipped with dual front
airbags.
²Side Curtain Airbags- Optional side curtain
airbags are available for this model when it is also
equipped with dual front airbags. This airbag systemis a passive, inflatable, Supplemental Restraint Sys-
tem (SRS) and vehicles with this equipment can be
readily identified by a molded identification trim but-
ton with the ªSRS - AIRBAGº logo located on the
headliner above each B-pillar (Fig. 2).
The supplemental restraint system includes the
following major components, which are described in
further detail elsewhere in this service information:
²Airbag Control Module- The Airbag Control
Module (ACM) is also sometimes referred to as the
Occupant Restraint Controller (ORC). The ACM is
located on a mount on the floor panel transmission
tunnel, below the center of the instrument panel.
Fig. 1 Supplemental Restraint System
1 - AIRBAG CONTROL MODULE
2 - PASSENGER AIRBAG
3 - PASSENGER AIRBAG ON/OFF SWITCH (STD CAB ONLY)
4 - DRIVER AIRBAG5 - SIDE CURTAIN AIRBAG (2)
6 - SIDE IMPACT SENSOR (2 - W/SIDE CURTAIN AIRBAGS
ONLY)
7 - SEAT BELT TENSIONER (2)
DRRESTRAINTS 8O - 3
RESTRAINTS (Continued)

Airbag Control Module (ACM). An airbag indicator in
the ElectroMechanical Instrument Cluster (EMIC)
illuminates for about six seconds as a bulb test each
time the ignition switch is turned to the On or Start
positions. Following the bulb test, the airbag indica-
tor is turned on or off by the ACM to indicate the
status of the supplemental restraint system. If the
airbag indicator comes on at any time other than
during the bulb test, it indicates that there is a prob-
lem in the supplemental restraint system electrical
circuits. Such a problem may cause airbags not to
deploy when required, or to deploy when not
required.
Deployment of the supplemental restraints
depends upon the angle and severity of an impact.
Deployment is not based upon vehicle speed; rather,
deployment is based upon the rate of deceleration as
measured by the forces of gravity (G force) upon the
impact sensors. When an impact is severe enough,
the microprocessor in the ACM signals the inflator of
the appropriate airbag units to deploy their airbag
cushions. The outboard front seat belt tensioners are
provided with a deployment signal by the ACM in
conjunction with the driver and passenger front air-
bags. During a frontal vehicle impact, the knee block-
ers work in concert with properly fastened and
adjusted seat belts to restrain both the driver and
the front seat passenger in the proper position for an
airbag deployment. The knee blockers also absorb
and distribute the crash energy from the driver and
the front seat passenger to the structure of the
instrument panel. The seat belt tensioner removes
the slack from the outboard front seat belts to pro-
vide further assurance that the driver and front seat
passenger are properly positioned and restrained for
an airbag deployment.
Typically, the vehicle occupants recall more about
the events preceding and following a collision than
they do of an airbag deployment itself. This is
because the airbag deployment and deflation occur
very rapidly. In a typical 48 kilometer-per-hour (30
mile-per-hour) barrier impact, from the moment of
impact until the airbags are fully inflated takes
about 40 milliseconds. Within one to two seconds
from the moment of impact, the airbags are almost
entirely deflated. The times cited for these events are
approximations, which apply only to a barrier impact
at the given speed. Actual times will vary somewhat,
depending upon the vehicle speed, impact angle,
severity of the impact, and the type of collision.
When the ACM monitors a problem in any of the
supplemental restraint system circuits or compo-
nents, including the seat belt tensioners, it stores a
fault code or Diagnostic Trouble Code (DTC) in its
memory circuit and sends an electronic message to
the EMIC to turn on the airbag indicator. Propertesting of the supplemental restraint system compo-
nents, the Programmable Communications Interface
(PCI) data bus, the electronic message inputs to and
outputs from the EMIC or the ACM, as well as the
retrieval or erasure of a DTC from the ACM or EMIC
requires the use of a DRBIIItscan tool. Refer to the
appropriate diagnostic information.
See the owner's manual in the vehicle glove box for
more information on the features, use and operation
of all of the factory-installed passive restraints.
WARNING
WARNINGS - RESTRAINT SYSTEM
WARNING: TO AVOID PERSONAL INJURY OR
DEATH, DURING AND FOLLOWING ANY SEAT BELT
OR CHILD RESTRAINT ANCHOR SERVICE, CARE-
FULLY INSPECT ALL SEAT BELTS, BUCKLES,
MOUNTING HARDWARE, RETRACTORS, TETHER
STRAPS, AND ANCHORS FOR PROPER INSTALLA-
TION, OPERATION, OR DAMAGE. REPLACE ANY
BELT THAT IS CUT, FRAYED, OR TORN.
STRAIGHTEN ANY BELT THAT IS TWISTED.
TIGHTEN ANY LOOSE FASTENERS. REPLACE ANY
BELT THAT HAS A DAMAGED OR INOPERATIVE
BUCKLE OR RETRACTOR. REPLACE ANY BELT
THAT HAS A BENT OR DAMAGED LATCH PLATE
OR ANCHOR PLATE. REPLACE ANY CHILD
RESTRAINT ANCHOR OR THE UNIT TO WHICH THE
ANCHOR IS INTEGRAL THAT HAS BEEN BENT OR
DAMAGED. NEVER ATTEMPT TO REPAIR A SEAT
BELT OR CHILD RESTRAINT COMPONENT.
ALWAYS REPLACE DAMAGED OR FAULTY SEAT
BELT AND CHILD RESTRAINT COMPONENTS WITH
THE CORRECT, NEW AND UNUSED REPLACEMENT
PARTS LISTED IN THE DAIMLERCHRYSLER MOPAR
PARTS CATALOG.
WARNING: TO AVOID PERSONAL INJURY OR
DEATH, ON VEHICLES EQUIPPED WITH AIRBAGS,
DISABLE THE SUPPLEMENTAL RESTRAINT SYS-
TEM BEFORE ATTEMPTING ANY STEERING
WHEEL, STEERING COLUMN, AIRBAG, SEAT BELT
TENSIONER, IMPACT SENSOR, OR INSTRUMENT
PANEL COMPONENT DIAGNOSIS OR SERVICE.
DISCONNECT AND ISOLATE THE BATTERY NEGA-
TIVE (GROUND) CABLE, THEN WAIT TWO MINUTES
FOR THE SYSTEM CAPACITOR TO DISCHARGE
BEFORE PERFORMING FURTHER DIAGNOSIS OR
SERVICE. THIS IS THE ONLY SURE WAY TO DIS-
ABLE THE SUPPLEMENTAL RESTRAINT SYSTEM.
FAILURE TO TAKE THE PROPER PRECAUTIONS
COULD RESULT IN ACCIDENTAL AIRBAG DEPLOY-
MENT.
DRRESTRAINTS 8O - 5
RESTRAINTS (Continued)

AIRBAG CONTROL MODULE
DESCRIPTION
The Airbag Control Module (ACM) is also some-
times referred to as the Occupant Restraint Control-
ler (ORC) (Fig. 7). The ACM is concealed below the
instrument panel center stack in the passenger com-
partment of the vehicle, where it is secured by three
screws to a stamped steel mounting bracket welded
onto the top of the floor panel transmission tunnel
just forward of the instrument panel center support
bracket. Concealed within a hollow in the center of
the die cast aluminum ACM housing is the electronic
circuitry of the ACM which includes a microproces-
sor, an electronic impact sensor, an electronic safing
sensor, and an energy storage capacitor. A stamped
metal cover plate is secured to the bottom of the
ACM housing with four screws to enclose and protect
the internal electronic circuitry and components.
An arrow printed on the label on the top of the
ACM housing provides a visual verification of the
proper orientation of the unit, and should always be
pointed toward the front of the vehicle. The ACM
housing has integral mounting flanges on three cor-
ners. The mounting flange to the left of the connector
receptacle has an integral locating pin on its lower
surface. Both left side flanges have round mounting
holes, while the flange on the right side has a slotted
mounting hole. A molded plastic electrical connector
with two receptacles, one containing twenty-four ter-
minal pins and the other containing thirty-two termi-
nal pins, exits the rearward facing side of the ACM
housing. These terminal pins connect the ACM to the
vehicle electrical system through two dedicated takeouts and connectors of the instrument panel wire
harness.
The impact sensor and safing sensor internal to
the ACM are calibrated for the specific vehicle, and
are only serviced as a unit with the ACM. In addi-
tion, there are unique versions of the ACM for light
and heavy-duty models, and for vehicles with or
without the optional side curtain airbags. The ACM
cannot be repaired or adjusted and, if damaged or
faulty, it must be replaced.
OPERATION
The microprocessor in the Airbag Control Module
(ACM) contains the supplemental restraint system
logic circuits and controls all of the supplemental
restraint system components. The ACM uses
On-Board Diagnostics (OBD) and can communicate
with other electronic modules in the vehicle as well
as with the DRBIIItscan tool using the Programma-
ble Communications Interface (PCI) data bus net-
work. This method of communication is used for
control of the airbag indicator in the ElectroMechani-
cal Instrument Cluster (EMIC) and for supplemental
restraint system diagnosis and testing through the
16-way data link connector located on the driver side
lower edge of the instrument panel. (Refer to 8 -
ELECTRICAL/INSTRUMENT CLUSTER/AIRBAG
INDICATOR - OPERATION).
The ACM microprocessor continuously monitors all
of the supplemental restraint system electrical cir-
cuits to determine the system readiness. If the ACM
detects a monitored system fault, it sets an active
and stored Diagnostic Trouble Code (DTC) and sends
electronic messages to the EMIC over the PCI data
bus to turn on the airbag indicator. An active fault
only remains for the duration of the fault, or in some
cases for the duration of the current ignition switch
cycle, while a stored fault causes a DTC to be stored
in memory by the ACM. For some DTCs, if a fault
does not recur for a number of ignition cycles, the
ACM will automatically erase the stored DTC. For
other internal faults, the stored DTC is latched for-
ever.
In standard cab models, the ACM also monitors a
resistor multiplexed input from the passenger airbag
on/off switch and provides a control output for the
Off indicator in the switch through a passenger air-
bag indicator driver circuit. If the passenger airbag
on/off switch is set to the Off position, the ACM turns
on the passenger airbag on/off switch Off indicator
and will internally disable the passenger airbag from
being deployed. The ACM also turns on the on/off
switch Off indicator for about seven seconds each
time the ignition switch is turned to the On position
as a bulb test. Following the bulb test, the ACM con-
trols the status of the Off indicator based upon the
Fig. 7 Airbag Control Module
1 - AIRBAG CONTROL MODULE
2 - ORIENTATION ARROW
3 - LABEL
4 - CONNECTOR RECEPTACLE (2)
DRRESTRAINTS 8O - 11

The passenger airbag on/off switch housing is con-
structed of molded plastic and has three integral
mounting tabs. These mounting tabs are used to
secure the switch to the back of the molded plastic
switch face plate with three small screws. The
molded plastic face plate also has three integral
mounting tabs that are used to secure the switch and
face plate unit to the instrument panel center bezel
with three additional screws. A molded plastic con-
nector receptacle on the back of the switch housing
connects the switch to the vehicle electrical system
through a dedicated take out and connector of the
instrument panel wire harness. The molded plastic
harness connector insulator is keyed and latched to
ensure proper and secure switch electrical connec-
tions. The passenger airbag on/off switch cannot be
adjusted or repaired and, if faulty or damaged, the
switch must be replaced.
OPERATION
The passenger airbag on/off switch allows the cus-
tomer to turn the passenger airbag function On or
Off to accommodate certain uses of the right front
seating position where airbag protection may not be
desired. See the owner's manual in the vehicle glove
box for specific recommendations on when to enable
or disable the passenger airbag. The Off indicator of
the switch will be illuminated whenever the switch is
turned to the Off position and the ignition switch is
in the On position.
The ignition key is the only key or object that
should ever be inserted into the key cylinder actuator
of the switch. The on/off switch requires only a par-
tial key insertion to fully depress a spring-loaded
locking plunger. The spring-loaded locking plunger
prevents the user from leaving the key in the switch.
The key will be automatically ejected when force is
not applied. To actuate the passenger airbag on/off
switch, insert the ignition key into the switch key
actuator far enough to fully depress the plunger, then
rotate the actuator to the desired switch position.
When the switch key actuator is rotated to its clock-
wise stop (the key actuator slot will be aligned with
the Off indicator), the Off indicator is illuminated
and the passenger airbag is disabled. When the
switch is rotated to its counterclockwise stop (the key
actuator slot will be in a vertical position), the Off
indicator will be extinguished and the passenger air-
bag is enabled.The passenger airbag on/off switch connects one of
two internal resistors in series between the passen-
ger airbag mux switch sense and passenger airbag
mux switch return circuits of the Airbag Control
Module (ACM). The ACM continually monitors the
resistance in these circuits to determine the switch
position that has been selected. When the switch is
in the Off position, the ACM provides a ground input
to the switch through the passenger airbag indicator
driver circuit, which energizes the Light-Emitting
Diode (LED) that illuminates the Off indicator of the
switch.
The ACM will also illuminate the Off indicator of
the switch for about seven seconds each time the
ignition switch is turned to the On position as a bulb
test. The ACM will store a Diagnostic Trouble Code
(DTC) for any fault it detects in the passenger airbag
on/off switch or Off indicator circuits, and will illumi-
nate the airbag indicator in the instrument cluster if
a fault is detected. For proper diagnosis of the pas-
senger airbag on/off switch or the ACM, a DRBIIIt
scan tool is required. Refer to the appropriate diag-
nostic information.
REMOVAL
WARNING: TO AVOID PERSONAL INJURY OR
DEATH, ON VEHICLES EQUIPPED WITH AIRBAGS,
DISABLE THE SUPPLEMENTAL RESTRAINT SYS-
TEM BEFORE ATTEMPTING ANY STEERING
WHEEL, STEERING COLUMN, AIRBAG, SEAT BELT
TENSIONER, IMPACT SENSOR, OR INSTRUMENT
PANEL COMPONENT DIAGNOSIS OR SERVICE.
DISCONNECT AND ISOLATE THE BATTERY NEGA-
TIVE (GROUND) CABLE, THEN WAIT TWO MINUTES
FOR THE SYSTEM CAPACITOR TO DISCHARGE
BEFORE PERFORMING FURTHER DIAGNOSIS OR
SERVICE. THIS IS THE ONLY SURE WAY TO DIS-
ABLE THE SUPPLEMENTAL RESTRAINT SYSTEM.
FAILURE TO TAKE THE PROPER PRECAUTIONS
COULD RESULT IN ACCIDENTAL AIRBAG DEPLOY-
MENT.
(1) Disconnect and isolate the battery negative
cable. Wait two minutes for the system capacitor to
discharge before further service.
(2) Remove the center bezel from the instrument
panel. (Refer to 23 - BODY/INSTRUMENT PANEL/
INSTRUMENT PANEL CENTER BEZEL -
REMOVAL).
(3) From the back of the center bezel, remove the
three screws that secure the passenger airbag on/off
switch and face plate unit to the back of the bezel
(Fig. 40).
(4) Remove the passenger airbag on/off switch and
face plate from the center bezel as a unit.
DRRESTRAINTS 8O - 43
PASSENGER AIRBAG ON/OFF SWITCH (Continued)