Lamps/Lighting - Interior

The interior lighting system for this model includes incandescent lighting on two separate circuits: the dome/courtesy lamp circuit and the panel lamps dimmer circuit. The lamps on the dome/courtesy circuit include:
- Cargo Lamps (7) - The standard equipment cargo lamps are integral to the Center High Mounted Stop Lamp (CHMSL) located on the roof rear header above the rear glass on the back of the cab. One cargo lamp bulb is behind a clear lens on each outboard side of the center red lens of the CHMSL. The cargo lamps are manually activated or deactivated by depressing the momentary cargo lamps push button of the headlamp switch on the instrument panel to illuminate the cargo area of the pick-up box.
- Center Dome/Reading Lamp (Mega Cab Only) (4) - Mega cab models have a center dome/reading lamp that is centered in the headliner just rearward of the front seat back. The center dome/reading lamp includes two bulbs and is switched by the door ajar switches or the interior lighting thumbwheel of the headlamp switch, but also includes two integral push button actuated switches.
- Front Dome or Dome/Reading Lamp (Standard Cab Except Overhead Console) (6) - On standard cab models the dome lamp is centered in the headliner near the back of the cab. The standard (base) dome lamp has a single bulb and is switched by the door ajar switches or the interior lighting thumbwheel of the headlamp switch. The optional dome/reading lamp is mounted in the same location but includes an integral switch that is actuated by depressing the lamp lens.
- Front Dome/Reading Lamps (Overhead Console) (5) - In vehicles equipped with an optional overhead console there are two dome/reading lamps that are integral to the overhead console, which is centered in the headliner near the windshield header. The overhead console lamps are switched by the door ajar switches or the interior lighting thumbwheel of the headlamp switch, but also have switches that are individually actuated by depressing their respective lamp lenses.
- Front Dome or Dome/Reading Lamp (Quad Cab/Mega Cab Except Overhead Console) (5) - On quad cab or mega cab models the front dome lamp is centered in the headliner near the windshield header. The standard (base) dome lamp has a single bulb and is switched by the door ajar switches or the interior lighting thumbwheel of the headlamp switch. The optional dome/reading lamp is mounted in the same location but also includes an integral switch that is actuated by depressing the lamp lens.
- Glove Box Lamp (2) - An optional glove box lamp with an integral switch is located at the upper right corner of the instrument panel glove box opening and illuminates whenever the glove box is opened.
- Rear Dome or Dome/Reading Lamp (Quad Cab/Mega Cab Only) (6) - The rear dome lamp on quad cab and mega cab models includes a single bulb and is switched by the door ajar switches or the interior lighting thumbwheel of the headlamp switch. This lamp is centered in the headliner near the back of the cab. The optional dome/reading lamp is mounted in the same location but includes an integral switch that is actuated by depressing the lamp lens.
- Vanity Lamps (3) - An optional single intensity vanity lamp is located on one side of a covered mirror on both the right and left sun visors, and is controlled by an integral vanity mirror cover-actuated switch.

Most controls on the instrument panel and other controls located elsewhere on the interior of the vehicle are illuminated for night visibility. Some have miniature incandescent bulbs or Light-Emitting Diode (LED) units that are soldered to internal circuit boards and are not serviceable. The replaceable incandescent bulbs or bulb/bulb holder units on the panel lamps dimmer circuits in this vehicle include:
- Center Bezel Lamp (1) - An optional center bezel lamp with a replaceable bulb is located on the underside of the instrument panel center bezel to illuminate the center console forward storage bin and cup holders.
- Compass Mini-Trip Control Illumination Lamps - The optional Compass Mini-Trip Computer (CMTC) has up to three replaceable bulb/bulb holder units to illuminate its controls.
- Heater-Air Conditioner Control Illumination Lamps - The single zone heater-air conditioner control panel has up to three replaceable bulb/bulb holder units to illuminate its controls. The illumination provisions for the dual zone heater-air conditioner control panel are not serviceable.

Other components of the interior lighting system for this model include:
- Door Ajar Switches - A door ajar switch is integral to the door latch mechanism of each front and rear door.
- 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 vertical thumbwheel for selecting the panel lamps dimming level and for interior lighting control. A Parade position of the thumbwheel illuminates all Vacuum Fluorescent Display (VFD) units at full brightness for visibility when driving in daylight with the exterior lighting turned On. There are also detent positions to turn on all interior courtesy lighting, and a Defeat position that overrides door ajar switch control of interior lighting.
- 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.

Hard wired circuitry connects the interior 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 interior 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.

The interior lighting systems can be divided into two general classifications based upon the circuit that controls their operation: The courtesy lamp circuit, or the panel lamps dimmer circuit. The optional center bezel lamp is actually controlled by a park lamps output of the Totally Integrated Power Module (TIPM), which energizes this circuit at a fixed intensity whenever the exterior lighting is illuminated. The hard wired circuits and components of the interior lighting systems may be diagnosed and tested using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. However, conventional diagnostic methods may not prove conclusive in the diagnosis of the ElectroMechanical Instrument Cluster (EMIC), or the Controller Area Network (CAN) data bus. The most reliable, efficient, and accurate means to diagnose the EMIC, the CAN data bus, or the electronic bus message inputs and outputs related to the various interior lighting systems requires the use of a diagnostic scan tool.

COURTESY LAMP CIRCUIT
Depending upon the selected vehicle options the courtesy lamp circuit may include the dome and dome/reading lamps located in the headliner near the windshield, between the front and rear seating, the cargo lamps located near the center of the rear roof header, the glove box lamp in the top of the glove box opening in the instrument panel, and the vanity lamps located in the sun visors. The lamps in the courtesy lamp circuit are provided with a path to ground at all times. The EMIC controls the output of battery voltage for the courtesy lamps in this circuit based upon hard wired inputs from the door ajar switches, the headlamp switch and the ignition switch.

After all of the ajar switch inputs to the EMIC transition to open, the EMIC will keep the courtesy lamps illuminated for about 30 seconds, then fade the lamps to off (theater dimming) over about three seconds. The EMIC also provides courtesy lamp operation based upon a resistor multiplexed input from the vertical thumbwheel on the headlamp switch, and provides an illuminated entry feature in response to certain electronic message inputs received from the Sentry Key REmote Entry Module (SKREEM) and the Occupant Restraint Controller (ORC) over the CAN data bus. A resistor multiplexed courtesy lamp defeat input from the vertical thumbwheel of the headlamp switch will cause the EMIC to override normal courtesy lamp operation based upon inputs from all of the ajar switches.

For those lamps on the courtesy lamp circuit with independent switching such as the standard or optional map/ reading lamps, the optional vanity lamps, and the glove box lamp the EMIC provides a battery voltage output to the switches through a separate circuit. The EMIC provides a battery saver (load shedding) feature for all courtesy lamps, which will automatically turn these lamps off if they are left on for more than about ten minutes with the ignition switch in the Off position.

PANEL LAMP DIMMER CIRCUIT
The panel lamps dimmer circuit actually includes several circuits. These circuits control the illumination and dimming level of the headlamp switch, the heater-air conditioner controls and the four-wheel drive selector switch. All lamps in the panel lamps dimmer circuits are provided a path to ground at all times through a hard wired ground circuit. These lamps illuminate based upon inputs to the EMIC from the rotary control knob and vertical thumbwheel of the headlamp switch. The control knob on the headlamp switch selects the exterior lights, while the thumbwheel selects the panel lamps intensity (dimming) level.

When the exterior lighting is turned On, the EMIC provides electronic dimming level messages to the radio and the Compass Mini-Trip Computer (CMTC) over the CAN data bus. The EMIC also supplies a 12-volt Pulse Width Modulated (PWM) output to all of the incandescent lamps through several panel lamps dimmer circuits. This shared PWM output synchronizes the selected illumination intensity level of all of the lamps in the panel lamps dimmer circuit.

The radio and the CMTC each use the dimming level messages to control the illumination intensity of both their Vacuum Fluorescent Display (VFD) units and their control lighting. In addition, when the thumbwheel of the headlamp switch is moved to the Parade/Funeral Mode detent position, all of the VFD units are illuminated at their full intensity levels for increased visibility when the vehicle is driven during daylight hours with the exterior lights turned On.