Dodge Ram Truck 1500-2500-3500. Manual — part 426

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Front Lamp Units (3) - A standard equipment front lamp unit is mounted to the front of each front fender
panel on either side of the grille opening.

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License Plate Lamps (9) - A standard equipment rear license plate lamp unit is mounted to each outboard
vertical surface of the license plate tub formation in the center of the rear bumper on pickup models. On cab
and chassis models the license plate lamp function is integral to the rear lamp unit.

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Rear Fender Marker Lamps (4) - Vehicles equipped with dual rear wheels have four individual rear fender
marker lamp units mounted to the rear fenders. An amber lamp is located forward of each rear wheel opening
and a red lamp is located rearward of each rear wheel opening.

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Rear Lamp Units (8) - On pick-up models a standard equipment rear lamp unit is mounted to the rear of each
quarter panel on either side of the tailgate opening. On cab and chassis models a rear lamp unit is mounted
on the outboard side of each frame rail near the rear of the vehicle.

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Tailgate Marker Lamp (7) - Vehicles equipped with dual rear wheels have a single red tailgate marker lamp
unit mounted to the center of the outer tailgate panel below the tailgate latch release handle.

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Underhood Lamp (2) - Vehicles equipped with this option have a single underhood lamp unit with an integral
automatic mechanical (non-mercury) switch. The lamp and switch unit is mounted to the underside of the inner
hood reinforcement above the right side of the engine compartment.

These exterior lighting lamp units and their controls are combined to provide the following exterior lighting features:

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Backup Lamps - The backup (or reverse) lamps include a bulb, reflector and lens that are integral to each
rear lamp unit.

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Brake Lamps - The brake (or stop) lamps include a bulb, reflector and lens that are integral to each rear lamp
unit, and the CHMSL bulb and lens.

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Daytime Running Lamps - Vehicles manufactured for sale in Canada illuminate the high beam filament of the
headlamp bulb in each front lamp unit to serve as the Daytime Running Lamps (DRL).

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Exterior Lamp Fail-Safe Operation - The EMIC provides a fail-safe feature which will automatically turn on all
exterior lamps when the ignition switch is in the On position and there is no detected input from the headlamp
switch.

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Exterior Lamp Load Shedding - The EMIC provides a battery saver feature which will automatically turn off
all exterior lamps that remain on with the ignition switch in the Off position after a timed interval of about five
minutes.

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Front Fog Lamps - The optional front fog lamps include the bulb, reflector and lens of each adjustable front
fog lamp unit.

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Hazard Warning Lamps - The hazard warning lamps include the right and left turn signal bulbs, reflectors and
lenses of each front and rear lamp unit.

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Headlamp Delay - On vehicles equipped with this optional feature, the low or high beam headlamps remain
illuminated for a dealer-programmable delay period of 30, 60 or 90 seconds when the headlamp switch is
turned to the Off position after the ignition switch has been turned to the Off position.

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Headlamps - The headlamps include a single, dual filament halogen bulb, an adjustable reflector and a clear
lens integral to each front lamp unit.

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Optical Horn - Also known as flash-to-pass, the beam selection function of the multi-function switch control
stalk has a momentary intermediate position that allows the headlamp high beams to be flashed momentarily,
without changing the headlamp beam selection.

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Park Lamps - The park lamps include the park and side marker bulbs, reflectors and lenses integral to each
front and rear lamp unit as well as the bulbs, reflectors and lenses of the rear license plate lamps. The cab
clearance lamps, the dual rear wheel rear fender marker lamps and tailgate marker lamp are also included In
the park lamps circuit of vehicles equipped with these optional exterior lamps.

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Turn Signal Lamps - The turn signal lamps include the turn signal bulbs, reflectors and lenses that are inte-
gral to the right and left front and rear lamp units.

Other components of the exterior lighting system for this model include:

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Backup Lamp Switch - A plunger-type backup lamp switch is installed through the transmission housing of
vehicles equipped with a manual transmission and is actuated by the shifter mechanism within the transmis-
sion when Reverse gear is selected. Depending upon the transmission model, either a stand-alone Transmis-
sion Range Sensor (TRS), or a TRS that is integral to the solenoid pack on the valve body performs the
backup lamp switch function on vehicles with an automatic transmission.

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Brake Lamp Switch - A plunger-type brake lamp switch is located on the steering column support bracket
under the instrument panel and is actuated by the brake pedal arm.

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Front Control Module - The Front Control Module (FCM) is integral to the Integrated Power Module (IPM).
The FCM/IPM is located in the engine compartment, near the battery and the Power Distribution Center (PDC).
(Refer to 8 - ELECTRICAL/POWER DISTRIBUTION - DESCRIPTION).

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Front Fog Lamp Relay - Vehicles equipped with optional front fog lamps have a front fog lamp relay located
in the Power Distribution Center (PDC).

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Headlamp Switch - A headlamp switch is located on the left side of the instrument panel, below and outboard
of the steering column. The headlamp switch includes a rotary knob for the park lamps and headlamps On or
Off. This rotary knob is pulled outward for selecting the optional front fog lamps on vehicles so equipped. The
headlamp switch also features a vertical thumbwheel for selecting the panel lamps dimming level, a Parade
mode to illuminate all Vacuum Fluorescent Display (VFD) units at full brightness for visibility when driving in
daylight with the exterior lighting turned On, for cargo lamp control and for interior lighting control.

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Instrument Cluster - The ElectroMechanical Instrument Cluster (EMIC) is also known as the Cab Control
Node (CCN) in this vehicle. The EMIC/CCN is located in the instrument panel above the steering column
opening, directly in front of the driver. (Refer to 8 - ELECTRICAL/INSTRUMENT CLUSTER - DESCRIPTION).

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Multi-Function Switch - The multi-function switch is located on the steering column, just below the steering
wheel. A control stalk that extends from the left side of the switch is used to select the turn signal lamps (right
or left) and to select the headlamp beam (low, high or optical horn). A push button that extends from the top
of the switch is used to select the hazard warning lamps.

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Park Brake Switch - A park brake switch is located on the park brake lever mechanism on the cowl side inner
panel below the instrument panel, to the left of the steering column.

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Park Lamp Relay - A park lamp relay is located in the Power Distribution Center (PDC) of all vehicles.

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Trailer Tow Relays - All vehicles are equipped with trailer tow relays installed in the Power Distribution Center
(PDC) in the engine compartment, one for the trailer right turn and brake lamps and the other for the trailer left
turn and brake lamps.

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Trailer Tow Wiring - Standard equipment in all vehicles is a 4-way trailer tow wire harness take out and a
4-pin light duty trailer tow connector that is located behind the rear bumper. An optional factory-installed trailer
tow package supplements the 4-way harness and connector with a 7-way trailer tow wire harness and a
sealed, heavy duty 7-pin trailer tow connector installed in the left side of the forward vertical surface of the
license plate tub formation in the center of the rear bumper. This optional trailer tow package also includes a
4-way electric trailer brake wiring provision and connector located on top of the large body harness connection
under the instrument panel to the left of the brake pedal, as well as an electric trailer brake pigtail harness and
an instruction card that are stored in the glove box when the vehicle is shipped from the factory.

Hard wired circuitry connects the exterior lighting system components to the electrical system of the vehicle. These
hard wired circuits are integral to several wire harnesses, which are routed throughout the vehicle and retained by
many different methods. These circuits may be connected to each other, to the vehicle electrical system and to the
exterior lighting components through the use of a combination of soldered splices, splice block connectors, and
many different types of wire harness terminal connectors and insulators. Refer to the appropriate wiring information.
The wiring information includes wiring diagrams, proper wire and connector repair procedures, further details on wire
harness routing and retention, as well as pin-out and location views for the various wire harness connectors, splices
and grounds.

OPERATION

Following are paragraphs that briefly describe the operation of each of the major exterior lighting systems. The hard
wired circuits and components of the exterior lighting systems may be diagnosed and tested using conventional
diagnostic tools and methods. Refer to the appropriate wiring information.

However, conventional diagnostic methods may not prove conclusive in the diagnosis of the ElectroMechanical
Instrument Cluster (EMIC) (also known as the Cab Control Node/CCN), the Front Control Module (FCM) (also
known as the Integrated Power Module/IPM), the Powertrain Control Module (PCM) or the Programmable Commu-
nications Interface (PCI) data bus. The most reliable, efficient, and accurate means to diagnose the EMIC, the FCM,
the PCM, the PCI data bus or the electronic bus message inputs and outputs related to the various exterior lighting
systems requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.

BACKUP LAMPS

The backup (or reverse) lamps have a path to ground at all times through a takeout and eyelet terminal of the left
headlamp and dash wire harness that is secured by a ground screw to the left inner fender support within the

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engine compartment. On vehicles with a manual transmission, the backup lamp switch provides battery voltage to
the backup lamps on the backup lamp feed circuit whenever the ignition switch is in the On position and the
Reverse position is selected with the transmission shift linkage. On vehicles with an automatic transmission, the
Transmission Range Sensor (TRS) provides battery voltage to the backup lamps on the backup lamp feed circuit
whenever the ignition switch is in the On position and the Reverse position is selected with the transmission shift
linkage.

BRAKE LAMPS

The brake (or stop) lamps each have a path to ground at all times through a takeout and eyelet terminal of the left
headlamp and dash wire harness that is secured by a ground screw to the left inner fender support within the
engine compartment. The Center High Mounted Stop Lamp (CHMSL) has a path to ground at all times through a
takeout and eyelet terminal of the instrument panel wire harness that is secured by a ground screw to the back of
the support structure of the instrument panel near the center. The brake lamps receive battery voltage from the
Front Control Module (FCM) on the right and left brake lamp feed circuits and the CHMSL receives battery voltage
from the brake lamp switch output circuit when the brake lamp switch is closed by the brake pedal arm.

DAYTIME RUNNING LAMPS

Vehicles manufactured for sale in Canada illuminate the high beam filament of both headlamp bulbs at a reduced
intensity when the engine is running and the exterior lamps are turned off. The FCM must be programmed with the
appropriate country code for this feature to be enabled. Once enabled, anytime the FCM receives electronic mes-
sages over the PCI data bus from the PCM indicating the engine is running and from the EMIC indicating the status
of the headlamp switch exterior lighting input is Off, the FCM provides a pulse width modulated voltage output to the
proper headlamp bulb filaments through the right and left high beam output circuits to produce illumination at a
reduced intensity.

FRONT FOG LAMPS

Vehicles equipped with optional front fog lamps include a front fog lamp relay installed in the PDC, and a front fog
lamp switch integral to the headlamp switch on the instrument panel. The front fog lamps have a path to ground at
all times through their connection to the headlamp and dash wire harness. The left headlamp and dash wire har-
ness has takeouts with eyelet terminals that are secured by ground screws to the left inner fender support within the
engine compartment. The EMIC monitors a hard wired multiplex input from the headlamp switch to determine
whether the fog lamps are selected, then sends electronic fog lamp switch status messages to the FCM over the
PCI data bus.

When the FCM receives a fog lamp status message it then controls front fog lamp operation by energizing or de-
energizing the front fog lamp relay control coil. The FCM also sends the appropriate electronic message back to the
EMIC to illuminate or extinguish the front fog lamp indicator. When the front fog lamp relay is energized, it provides
battery voltage from a fused B(+) fuse in the PDC to the fog lamps through the fog lamp relay output circuit. The
FCM will automatically de-energize the front fog lamps relay any time the headlamp high beams are selected. The
EMIC also provides a battery saver (load shedding) feature for the front fog lamps, which will turn these lamps off
if they are left on for more than about five minutes with the ignition switch in the Off position. Each front fog lamp
includes an integral adjustment screw to be used for static aiming of the fog lamp beams.

HAZARD WARNING LAMPS

The hazard warning system includes the EMIC, the FCM and the multi-function switch on the steering column. The
EMIC monitors a hard wired multiplex input from the multi-function switch to determine the status of the hazard
warning switch, then sends the appropriate electronic hazard switch status messages to the FCM over the PCI data
bus. The FCM responds to these messages by controlling a battery voltage output and the flash rate for each of the
right and left turn signal lamps. The FCM also sends the appropriate electronic messages back to the EMIC to
control the illumination and flash rate of the right and left turn signal indicators, as well as to control the click rate
of an electromechanical relay soldered onto the EMIC electronic circuit board that emulates the sound emitted by a
conventional hazard warning flasher.

HEADLAMPS

The headlamp system includes the EMIC, the FCM, the multi-function switch on the steering column and the head-
lamp switch on the instrument panel. The headlamp bulbs have a path to ground at all times through their connec-
tion to the headlamp and dash wire harness. The headlamp and dash wire harness has takeouts with eyelet
terminals that are secured by ground screws to the right (right headlamp bulb) and left (left headlamp bulb) inner

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fender support within the engine compartment. The EMIC monitors a hard wired multiplex input to determine the
status of the headlamp switch, and a hard wired multiplex input from the multi-function switch to determine whether
the high or low beams are selected. The EMIC then sends the appropriate electronic headlamp switch and head-
lamp beam select switch status messages to the FCM over the PCI data bus.

The FCM responds to these messages by providing a pulse width modulated voltage output to the proper headlamp
bulb through the right and left low and high beam output circuits to illuminate the selected headlamp filaments. The
FCM also remembers which beams (low or high) were selected when the headlamps were last turned Off, and
energizes those beams again the next time the headlamps are turned On. The EMIC provides a battery saver (load
shedding) feature for the headlamps, which will turn these lamps off if they are left on for more than about five
minutes with the ignition switch in the Off position. The EMIC provides a fail-safe feature for the headlamps, which
will send an electronic message to the FCM to turn the low beam headlamps On automatically if it detects no input
from the headlamp switch. Each headlamp includes an integral reflector adjustment screw to be used for static aim-
ing of the headlamps.

PARK LAMPS

The park lamps system includes the EMIC, the FCM, a park lamp relay installed in the PDC, and the headlamp
switch on the instrument panel. The front park lamp and side marker lamp bulbs each have a path to ground at all
times through their connection to the headlamp and dash wire harness. The headlamp and dash wire harness has
takeouts with eyelet terminals that are secured by ground screws to the right (right park lamp and side marker lamp
bulbs) and left (left park lamp and side marker lamp bulbs) inner fender support within the engine compartment. The
rear park lamp, side marker lamp, license plate lamp and the optional fender and tailgate marker lamp bulbs have
a path to ground at all times through a takeout and eyelet terminal of the left headlamp and dash wire harness that
is secured by a ground screw to the left inner fender support within the engine compartment. The optional cab
clearance lamps each have a path to ground at all times through a takeout and eyelet terminal of the instrument
panel wire harness that is secured by a ground screw to the back of the support structure of the instrument panel
near the center.

The EMIC monitors a hard wired multiplex input from the headlamp switch, then sends the appropriate electronic
headlamp switch status messages to the FCM over the PCI data bus. The FCM responds to these messages by
energizing or de-energizing the park lamp relay. When the park lamp relay is energized, it provides battery voltage
from a fuse in the PDC through a park lamp relay output circuit to the appropriate lamp bulbs. The FCM provides
a battery saver (load shedding) feature for the park lamps, which will turn these lamps off if they are left on for more
than about five minutes with the ignition switch in the Off position. The EMIC provides a fail-safe feature for the park
lamps, which will send an electronic message to the FCM to turn these lamps on automatically if it detects no input
from the headlamp switch.

TRAILER TOW WIRING

In addition to the trailer tow wiring provisions, all vehicles include right and left trailer tow stop/turn relays installed
in the PDC. When the FCM receives the appropriate inputs for normal turn signal, hazard warning or brake lamp
operation, it responds by also energizing or de-energizing these trailer tow relays. When a trailer tow relay is ener-
gized, it provides battery voltage from a fused B(+) fuse to the trailer lamps through the trailer tow wiring to syn-
chronize the illumination and flash rate of the trailer brake and turn signal lamps with those of the tow vehicle.

TURN SIGNAL LAMPS

The turn signal lamps system includes the EMIC, the FCM and the multi-function switch on the steering column.
The front turn signal lamp bulbs each have a path to ground at all times through their connection to the headlamp
and dash wire harness. The headlamp and dash wire harness has takeouts with eyelet terminals that are secured
by ground screws to the right (right front turn signal lamp bulb) and left (left front turn signal lamp bulb) inner fender
supports within the engine compartment. The rear turn signal lamp bulbs have a path to ground at all times through
a takeout and eyelet terminal of the left headlamp and dash wire harness that is secured by a ground screw to the
left inner fender support within the engine compartment.

The EMIC monitors a hard wired multiplex input from the multi-function switch to determine the status of the turn
signal switch, then sends the appropriate electronic turn signal switch status messages to the FCM over the PCI
data bus. The FCM responds to these messages by controlling a battery voltage output and the flash rate for either
the right or left turn signal lamps. The FCM also sends the appropriate electronic messages back to the EMIC to
control the illumination and flash rate of the right or left turn signal indicators, as well as to control the click rate of
an electromechanical relay soldered onto the EMIC electronic circuit board that emulates the sound emitted by a
conventional turn signal flasher.

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