2021 Peterbilt 389 Bulb Sizes (Headlight, Tail, Fog)

Quick Reference

The 2021 Peterbilt 389, a true icon on the road, offers a blend of classic styling and modern functionality. When it comes to lighting, Peterbilt provided options, meaning that your specific 389 might have different bulb types depending on the original factory configuration. Many 389s came equipped with traditional halogen headlights, while others featured advanced LED lighting systems, particularly for the low and high beams. It's crucial to check your specific truck's configuration before purchasing replacement bulbs.

For halogen-equipped models, the low beams commonly use an H11 bulb, providing a standard, yellowish light output. High beams on these models typically utilize an H9 bulb, offering a brighter, more focused beam for maximum visibility. If your 389 came with factory LED headlights, these systems are generally integrated units and do not have replaceable individual bulbs for the low and high beams. Instead, if a component fails, the entire housing or module often needs replacement.

Fog lights, a valuable aid in adverse weather, almost universally employ an H10 bulb across the various trims of the 2021 Peterbilt 389. Daytime Running Lights (DRLs), essential for daytime visibility, commonly use a 7443 incandescent bulb. Both front and rear turn signals, as well as the brake lights, tail lights, and reverse lights, often share the versatile 3157 incandescent bulb. This bulb is a dual-filament type, allowing for both dim (tail light/running light) and bright (brake/turn signal) functions in a single unit. For license plate illumination and side markers, the smaller 194 incandescent bulb is frequently used. Inside the cab, the dome and map lights typically utilize a 578 festoon bulb, providing interior illumination.

LED vs Halogen Upgrade Considerations

Upgrading your 2021 Peterbilt 389 from halogen to LED bulbs can significantly enhance visibility, modernize the truck's appearance, and reduce power consumption. However, there are several key considerations:

• CANBUS Errors: Modern vehicles, including the Peterbilt 389, often use a Controller Area Network Bus (CANBUS) system to monitor electrical components. LED bulbs draw significantly less power than halogens, which can trick the CANBUS system into thinking a bulb is out, triggering