2014 Freightliner M2 106 Bulb Size Chart: Headlight, Tail, Fog & More

As an ASE-certified master technician, I’ve serviced countless medium-duty commercial trucks, and the 2014 Freightliner M2 106 is one of the most common workhorses in the fleet industry. Whether your M2 106 is outfitted as a box truck, flatbed, or tow truck, maintaining proper lighting is essential for DOT compliance and driver safety.

Because the M2 106 is often customized by different body builders, your rear lighting may vary. However, the cab and chassis lighting remains standardized. Below is a comprehensive guide to the bulb sizes for the 2014 Freightliner M2 106, including differences between composite and sealed-beam headlight options.

Quick Reference: 2014 Freightliner M2 106 Bulb Sizes

The M2 106 was offered with two main headlight configurations: aerodynamic composite housings (standard on many highway models) and traditional sealed beam housings (often used on vocational setups).

Note: Rear lighting (tail, brake, reverse, and rear turn) heavily depends on the upfitter/body builder. Many modern upfits use sealed 4-inch round or 6-inch oval LED modules rather than replaceable incandescent bulbs.

LED vs Halogen Upgrade Considerations

Upgrading your 2014 Freightliner M2 106 to LED lighting is highly recommended for fleet applications due to the extended lifespan and improved visibility. However, there are a few things to keep in mind:

• CANBUS Systems and Hyperflashing: The M2 chassis uses a sophisticated multiplex wiring system (the Bulkhead Module, or BHM). If you swap standard 3157 turn signal bulbs for LEDs, the lower resistance can cause hyperflashing or trigger a "bulb out" warning on the dash. You will likely need in-line load resistors or CANBUS-ready LED bulbs to trick the system.
• Headlight Housings: If upgrading composite headlights (9005/9006) to LED, ensure the LED diode alignment matches the original halogen filament orientation to prevent scattering light and blinding oncoming traffic. If you have H6054 sealed beams, you can replace the entire housing with a DOT-approved LED sealed beam replacement.
• Clearance Issues: Some high-output LED headlight bulbs have large cooling fans or heat sinks. The M2's composite headlight housing can be tight at the rear, so double-check clearance before purchasing.

How to Replace Each Bulb

• Headlights (Composite): Open the hood. The rear of the headlight assembly is easily accessible. Twist the locking ring counterclockwise, pull the bulb straight out, and disconnect the wiring harness. Avoid touching the new halogen glass with bare hands.
• Headlights (Sealed Beam): Remove the Torx or Phillips screws holding the metal retaining ring on the front of the bezel. Pull the glass housing forward and unplug the 3-prong connector.
• Front Turn Signals: Located in the same composite housing or the bumper (depending on trim). Reach behind the assembly, twist the bulb socket a quarter-turn counterclockwise, and swap the 3157A bulb.
• Cab Marker Lights: Access requires removing the two Phillips screws on the amber lens on the roof. Pull the lens off to expose the 194 bulb. Reseal with a tiny bit of dielectric grease to prevent moisture intrusion.
• Tail/Brake/Reverse Lights: If your truck has standard 3157/3156 chassis boxes, simply unscrew the rear lens. If you have sealed 4-inch rubber grommet lights, use a flathead screwdriver to gently pry the light assembly out of the grommet and unplug the 3-pin pigtail.
• Interior Dome Light: Gently pry the plastic lens cover off the overhead console using a plastic trim tool. The 578 festoon bulb snaps in and out of the metal spring clips.

Common Lighting Issues for This Generation

The 2014 Freightliner M2 106 is generally reliable, but its lighting system is prone to a few specific issues. The Bulkhead Module (BHM) and Chassis Module (CHM) are responsible for distributing power to the lights without traditional fuses. If a wire shorts out, the module will cut power to that circuit to protect itself. If you replace a burnt bulb but it still doesn't work, you may need a technician to clear the fault code in the module or trace a wiring short along the frame rail.

Additionally, moisture intrusion in the front composite headlight housings is incredibly common on the M2 platform, which can cause premature bulb failure.

If you are dealing with complex multiplex wiring issues or just want a professional to upgrade your fleet's lighting, find a trusted shop on Repairius.