CURT 4-Way Flat Trailer Wiring Harness for Ram ProMaster 1500/2500/3500 — Plug-in OEM Fit with Dust Cover

CURT 56478 is a vehicle-side, plug-and-play 4-way flat trailer wiring harness engineered to fit select Ram ProMaster 1500, 2500, and 3500 models and provide a reliable trailer lighting connection without cutting or splicing.

If your ProMaster lacks factory trailer wiring, this custom-fit CURT harness delivers a fast, OEM-compatible solution. The harness uses vehicle-specific connectors that plug into the existing taillight sockets, supplying a standard 4-way flat output for tail lights, brake lights and turn signals. Designed for easy installation and durable operation, it includes a dust cover and built-in circuitry to ensure consistent performance on the road.

How does this harness install on my Ram ProMaster?

Installation is straightforward: the harness uses the factory taillight connectors so there is no cutting, splicing, or soldering required. You remove the taillight access panel, unplug the vehicle connectors and plug in the CURT T-connector. The 4-way flat socket mounts near the hitch for convenient trailer connection.

• Direct plug-in to vehicle taillight assembly — no wire modifications
• Includes dust cover to protect the connector when unused
• Hardware and wiring included for a neat, secure routing
• Designed for specific ProMaster model years—check fitment

What functions and wiring does the 4-way flat support?

The CURT 4-way supplies standard lighting circuits required by most small trailers and utility trailers: running lights, turn signals and brake lights. It uses a tail light converter to adapt the vehicle signals to the trailer's wiring when needed, keeping the trailer lights synchronized with the van's outputs.

• Running/parking lights, left/right turn signals, and stop lights
• 4-way flat connector compatible with common trailer plugs
• Built-in tail light converter for signal compatibility
• SMT circuitry for reliable signal processing and longevity

Will this harness withstand regular towing and exposure?

CURT designs its vehicle-side harnesses for everyday towing conditions, using durable components and SMT circuitry to reduce failure points. The dust cover helps keep moisture and debris out of the connector, and the wiring and terminals are routed to minimize stress from movement or road impacts.

• SMT (surface-mount technology) circuitry for improved durability
• Protective dust cap to keep connector clean and dry
• Robust wiring and secure mounting points to resist vibration
• OEM-compatible connectors to maintain factory-like fit and finish

How do I confirm compatibility for my vehicle?

Compatibility depends on the ProMaster model year and trim; always verify fitment details before purchase. Check the product application list or enter your vehicle details on the retailer’s compatibility tool to ensure the CURT 56478 matches your specific ProMaster 1500, 2500, or 3500.

• Verify model year and trim against the application information
• Use VIN or vehicle lookup tools where available for accuracy
• Contact CURT or your vendor if fitment questions remain

Who is this for? The CURT 56478 harness is ideal for ProMaster owners who need a clean, factory-style trailer wiring solution without permanent modifications. It's suited for contractors, outdoor enthusiasts, and small-business van operators who tow trailers occasionally or frequently and prefer a secure, easy-to-install electrical hookup that maintains the vehicle’s original wiring integrity.