2021+ Ford F-150 STX 4257 WT21 White LED Reverse Backup Bulbs With Built-In Resistors, No Error Codes (Pair)

2021+ Ford F-150 STX 4257 WT21 LED Reverse Backup Bulbs| Built-in Resistors, No Error Codes (PAIR)

Upgrade the factory halogen reverse lights on your 2021+ Ford F-150 STX with compatible 4257 WT21 white LED reverse backup bulbs. Each bulb produces 1200 lumens through 54 SMD LEDs with 360° coverage, giving the reverse-light housing broader illumination when backing up, parking, or using the rear camera at night.

The plug-and-play design lets you replace the factory incandescent reverse bulbs with 4257 LEDs without cutting, rewiring, or splicing.

1200-Lumen White LED Output

Each 4257 WT21 bulb uses 54 SMD LEDs and produces 1200 lumens of white light. The 360° design spreads light throughout the housing instead of concentrating the output in one direction, providing broader illumination behind the truck.

Built-In Resistor for CANBUS Systems

LED bulbs draw 80% to 90% less power than halogen bulbs while providing the same or higher level of brightness. Replacing a halogen bulb with an LED can change the electrical load, and your Ford truck's CANBUS system may detect it as a bulb failure, causing flickering and dashboard warning lights even if it's working properly. These bulbs use a built-in resistor which is positioned on the turn-signal filament to help prevent error codes, fast blinking, and signs of hyperflash.

Full-Metal Heatsink and Cooling Fan

A full-metal heatsink works with the built-in cooling fan to manage operating heat. The fan activates when needed to reduce heat around the resistor and help protect the LED from prolonged thermal exposure. This increases the average lifespan and efficiency of the bulb.

4257 Bulb Cross Reference

Common 4257 cross-reference numbers include:

• 4257
  
• 4257A
  
• 4257NA
  
• 4257NALL
  
• 4257NAK
  
• 4257AK
  

The 3156 and 3157 are also frequently associated with the 4257 family, particularly in aftermarket LED applications, but they are not automatically interchangeable in every vehicle because the base design and socket fit can differ.

Always confirm the original bulb number and vehicle application before ordering.

Plug-and-Play Installation

Installation is beginner-friendly and takes about 10 minutes. Remove the factory reverse bulb, install the 4257 WT21 LED replacement, and reconnect the socket.

No cutting, splicing, complicated wiring, or external resistor installation is required.

Works for 99.9% of vehicles

CA Residents: WARNING: Cancer and Reproductive Harm - www.P65Warnings.ca.gov

Do you have questions about the application, installation, shipping, warranty, or more? Do not hesitate to reach out to Underground Lighting and talk to a specialist. Chat with us online by hitting the chat button or call us at (561) 918-5225. We are here to help!