2015 Peterbilt 389 Bulb Sizes (Headlight, Tail, Fog)

As an ASE-certified master technician with years of experience working on heavy-duty commercial trucks, I know that maintaining proper lighting on a Class 8 truck is critical for both safety and DOT compliance. The 2015 Peterbilt 389 is an absolute icon on the highway, seamlessly blending classic styling with modern PACCAR electronics. If you are preparing to replace a burnt-out bulb or looking to upgrade your rig to LEDs for better nighttime visibility, having the exact bulb sizes is step one.

Here is your comprehensive guide to the 2015 Peterbilt 389 bulb sizes, replacement tips, and upgrade considerations.

Quick Reference

Note: The Peterbilt 389 was offered with different headlight setups, including sealed beams, composite halogen pods, and factory LED options. The chart below reflects the standard composite halogen housings and incandescent bulbs. Many commercial trucks of this vintage utilize sealed LED units for the rear and marker lights straight from the factory or upfitter.

If your 389 is equipped with classic 4x6 sealed beams rather than the composite projector pods, your sizes will be H4656 (Low/High) and H4651 (High). Ensure you check your specific headlight pod design before purchasing.

LED vs Halogen Upgrade Considerations

Upgrading a 2015 Peterbilt 389 to LED lighting is one of the most popular and practical modifications for owner-operators. However, because modern PACCAR electrical systems utilize a chassis node (chassis control module) to monitor bulb resistance, dropping in aftermarket LEDs isn't always plug-and-play.

CANBUS Errors and Anti-Flicker: The truck's computer sends a small pulse of electricity to check if a bulb is burnt out. Because LEDs draw significantly less power than halogens, the system may think the bulb is dead, resulting in dash warnings, fast-flashing turn signals, or headlight flicker. To solve this, you will need LED bulbs with built-in CANBUS decoders, or you must install inline load resistors.

Sealed LED Upgrades: For the tail lights, turn signals, and cab markers, the best upgrade route is entirely replacing the fixture with a sealed, DOT-approved LED housing (like those from Grote, Truck-Lite, or Maxxima) rather than swapping the internal bulb. This prevents moisture intrusion, which is the number one killer of truck lighting.

How to Replace Each Bulb

Headlights (Low and High Beam): If you have the composite pod headlights, access is gained by removing the rear dust cover on the back of the headlight bucket. You may need to tilt the hood forward and turn the wheel to get adequate clearance. Twist the H11 or 9005 bulb counterclockwise to release it. Be careful not to touch the glass of the new halogen bulb with your bare fingers, as oil can cause premature failure.

Front Turn Signals & Marker Lights: These are usually located on the fender or alongside the headlight pod. Remove the Phillips screws securing the amber lens. Pull the bulb straight out of the socket and press the new 3157 or 194 bulb in. Use dielectric grease on the socket to prevent corrosion from road salt and grime.

Rear Tail, Brake, Turn, and Reverse Lights: Most 389 setups utilize rubber grommet-mounted 4-inch round lights. To replace these, you don't actually change a bulb. You pry the entire sealed light unit out of the rubber grommet using a flathead screwdriver or trim tool, unplug the 3-prong pigtail, and press a new sealed LED unit into the existing grommet.

Cab Roof/Marker Lights: The iconic torpedo lights on the roof are held on by two screws. Remove the lens, swap the 194 bulb, and ensure the rubber gasket is intact before reinstalling. If the gasket is cracked, replace it to prevent a roof leak.

Interior Dome/Map Lights: Use a plastic trim pry tool to gently pop off the overhead console lenses. The festoon (211-2) bulbs are held by tension springs. Pull them free and snap the new ones in place.

Common Lighting Issues for this Generation

Chassis Node Faults: The 2015 PACCAR electrical system is sensitive. A short circuit in a trailer harness can sometimes cause the chassis node to cut power to that specific lighting circuit to protect the computer. If a new bulb doesn’t work, you may need a diagnostic scan tool to clear the lighting fault from the chassis module.

Headlight Pod Condensation: The composite headlight housings on the 389 are notorious for collecting condensation. Check the rear dust caps and the perimeter seal. If moisture builds up, it will rapidly blow halogen bulbs.

Grounding Issues: Commercial trucks take a beating from vibration and road debris. If your tail lights are acting erratically or your turn signals cause your marker lights to blink, you almost certainly have a corroded frame ground. Trace the ground wire from the light bracket to the frame and clean it with a wire brush.

Keeping your Pete 389 fully illuminated keeps you moving safely down the road. If you are experiencing electrical faults, CANBUS issues, or need help installing a full LED conversion kit, don't leave it to chance. Find a trusted shop on Repairius.