2016 Peterbilt 389 Bulb Size Guide: Headlights, Tail Lights & More

As an ASE-certified master technician, I’ve worked on countless heavy-duty trucks, and the Peterbilt 389 is an undisputed classic. However, keeping the road lit during long overnight hauls is critical for safety and DOT compliance. The 2016 Peterbilt 389 blends traditional aesthetics with modern needs, meaning it can come equipped with standard halogen setups, sealed beams, or full OEM LED lighting depending on how the truck was specced from the factory or modified by fleets.

Below is your comprehensive bulb size guide for the 2016 Peterbilt 389, covering everything from headlights to cabin dome lights.

Quick Reference

*Note: The 389 is highly customizable. Many feature the classic dual rectangular 4x6 housings (H4656/H4651). Others feature single 7-inch round housings (H6024). By 2016, many operators opted for drop-in LED sealed beam replacements direct from the factory or dealership.

LED vs Halogen Upgrade Considerations

Upgrading a Class 8 truck like the Peterbilt 389 to LED lighting is one of the most common and practical modifications you can make. It dramatically reduces electrical draw and vastly improves nighttime visibility.

• Sealed Beam Upgrades: If your 389 has standard 4x6 or 7-inch round halogen sealed beams, you can swap the entire housing out for DOT-approved LED projectors or reflectors (like JW Speaker or Truck-Lite). These are usually plug-and-play with standard H4/3-prong pigtails.
• CANBUS Errors & Hyperflashing: While older heavy-duty trucks didn't heavily monitor bulb resistance, a 2016 Peterbilt features a modern body control module. Swapping standard incandescent turn signals (like the 1157 or 3157) to LED bulbs without built-in resistors can cause hyperflashing or dash warnings. You may need load resistors or a heavy-duty LED-compatible flasher relay.
• Vibration Resistance: When selecting LED upgrades for a heavy-duty truck, always choose bulbs and sealed units with high shock and vibration ratings. Standard automotive LEDs will quickly fail in a commercial trucking environment.

How to Replace Each Bulb

• Headlights (Low/High Beam): For the classic external pods, replacing a sealed beam is straightforward. Remove the Phillips screws holding the stainless or chrome bezel, pull the retaining ring off, and disconnect the 3-prong harness. Apply dielectric grease to the new connections to prevent corrosion.
• Fog Lights: Fog lights are typically bumper-mounted. Access the rear of the housing from behind the bumper. Twist the bulb cap counter-clockwise and unplug the harness.
• Front Turn Signals: Located either in the headlight pod or fender-mounted. Remove the exterior lens screws. Push the 1157 bulb in and twist counter-clockwise to release.
• Rear Stop/Tail/Turn & Reverse: By 2016, most 389s utilize standard 4-inch round grommet-mounted LEDs. To replace, simply pry the light assembly out of the rubber grommet with a flathead screwdriver and unplug the 3-prong pigtail on the back.
• Cab Clearance / Marker Lights: These bullet or teardrop-style lights on the roof often use 194 bulbs or are entirely sealed LED units. Remove the two screws on the lens. If sealed, you must cut and splice (or unplug) the wire harness inside the headliner or roof channel.
• Interior Dome/Map Lights: Carefully pry the plastic lens covers off the overhead console using a plastic trim tool. The 211-2 festoon bulbs simply pop out of their spring-loaded tension clips.

Common Lighting Issues for this Generation

1. Corroded Pigtails & Connectors: The 389 sees hundreds of thousands of miles in rain, snow, and road salt. The 3-prong pigtails behind the headlights and rear tail lights are notorious for corroding, leading to dim or flickering lights. Always check the ground wires!
2. Sealed Beam Condensation: Cheaper aftermarket sealed beam housings can develop poor seals over time, causing condensation. This can blow halogen bulbs prematurely.
3. Frayed Wiring Harnesses: Due to chassis vibration, wiring harnesses running along the frame rails to the rear tail lights can chafe. If you lose all rear lighting on one side, check for a rubbed-through wire near the frame crossmembers.

Proper lighting keeps you moving and keeps the DOT inspectors happy. If you are experiencing complex wiring harness issues or multiplexing faults, don't leave it to chance. Find a trusted shop on Repairius.