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2021 - 2024 BMW X4
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Always the correct part
We know our products
Quality Products
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Installation Point(s): S3, S4
Plugs into vehicle tail light assembly to provide a 4-way flat socket
Simple plug-and-play design eliminates the need for cutting or splicing
Plugs into vehicle tail light assembly to provide a 4-way flat socket
Finish: Blank
Material: THERMOPLASTIC RUBBER
Warranty: One-Year Limited Warranty
If your vehicle is not equipped with wiring for towing a trailer, CURT custom wiring is the ideal solution. A custom wiring harness -- also called a T-connector -- is a simple, plug-and-play electrical device that plugs into your automotive electric system and provides a standard, universal trailer wiring connection. This is done using two or more vehicle-specific, OEM-compatible connectors to plug into the taillight assembly, eliminating the need for cutting, splicing and soldering during installation. Custom wiring harnesses are made vehicle-specific, and while they are not available for all vehicles, they do offer one of the fastest, easiest and most secure ways to wire a vehicle for towing. This particular plug-in harness provides a 4-way flat connector socket and is designed to be a custom wiring harness to fit certain years of the BMW X4 (to verify your vehicle compatibility, see application info). It comes with all necessary wiring components to establish a reliable trailer wiring connection, as well as a dust cover to keep the connector clean when not in use. You have a picture in mind of your next destination -- maybe it's the boat landing at your favorite fishing spot, maybe it's a campsite that overlooks one of nature's masterpieces, or maybe it's the next big jobsite. However, turning that picture into a reality takes more than just daydreaming. It takes a solid connection and the right amount of power. CURT custom wiring is made with some of the most sophisticated technology in the industry and is designed to install with ease, giving you a long-lasting electrical connection for your towing hitch setup.
CURT offers a variety of high-quality trailer hitches and accessories for select vehicle models. Find the perfect fit for your towing needs at TowUniverse.
CURT, a Lippert brand, offers a complete line of towing products and is the leading manufacturer of custom-fit trailer hitches. We offer the broadest selection of custom-fit hitches, and each one is designed, welded, and coated in Wisconsin.
CURT is also a leader in flat towing products, as well as 5th wheel, gooseneck, and weight distribution hitches, ball mounts, electrical components, cargo solutions, and other towing accessories.
For everything from passenger cars and vans to full-size pickups and SUVs, CURT is 'The First Name in Towing Products®.'
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Call 888-634-9494One-year limited
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1 compatible vehicles
| Year | Make & Model | Notes |
|---|---|---|
| 2021 - 2024 | BMW X4 | — |
The CURT 56557 Vehicle-Side Custom 4-Pin Trailer Wiring Harness, Fits Select BMW X4 (Part #BKDK56557) fits the following vehicles: 2021-2024 BMW X4. Always verify your specific year, make, and model before ordering.
The CURT 56557 Vehicle-Side Custom 4-Pin Trailer Wiring Harness, Fits Select BMW X4 (Part #BKDK56557) fits 2021-2024 BMW X4 models. The 2024 model year is the last year covered by this part number. For newer models, check for an updated version.
Yes, the CURT 56557 Vehicle-Side Custom 4-Pin Trailer Wiring Harness, Fits Select BMW X4 (Part #BKDK56557) is designed to fit the 2021-2024 BMW X4.
The CURT 56557 Vehicle-Side Custom 4-Pin Trailer Wiring Harness, Fits Select BMW X4 (Part #BKDK56557) Refer to the included instructions for installation details. Basic hand tools are typically all you need.
Curt 56557 is a wiring location guide and powered converter lead system designed for SUVs and vans. It provides a lighting module that converts vehicle taillight signals to a 4-flat trailer connector, allowing you to tow a trailer with integrated lighting. The system includes signal circuits (5.0 amps per side) and tail/running circuits (7.0 amps total).
Curt 56557 is designed for SUVs and vans. The manual does not specify which makes, models or years are compatible. Contact Curt Manufacturing or your retailer with your vehicle's year, make and model to confirm fitment before purchasing.
The manual does not address compatibility with factory towing packages or integrated trailer modules. Contact Curt Manufacturing or a professional installer to confirm whether 56557 can be used alongside factory equipment.
No. The powered converter lead is designed only for 12-volt negative ground electrical systems. It cannot be used on 24-volt systems or vehicles with positive ground systems.
Required tools are: ratchet, Phillips screwdriver, 6" extension, trim panel tool, 10mm socket, 10mm wrench, wire cutter, wire crimper, drill, wire stripper, 3/32" drill bit, and test light. A test light or functioning trailer is needed to verify proper function after installation.
The kit includes a lighting modules box with double-sided tape and epoxy, a 4-flat connector with dust cover, a 15-amp fuse and fuse holder, cable ties, a white 16 GA ground wire with ring terminal, a black 12 GA power wire, connectors with yellow and red wires (left turn and brake), a green wire connector (right turn), and a brown wire connector (taillight). A screw for ground wire attachment is also provided.
Yes. You must disconnect the negative battery cable using a 10mm socket before beginning installation. Isolate the negative cable and ensure it does not touch any metal objects, as grounding it to metal could damage the vehicle's electrical system. Reconnect the battery only after all other installation steps are complete and the fuse is installed.
You must remove: the hatch floor coverings and privacy panel (being careful not to break locking tabs or pins), the rear side cargo panel from the driver's side, the rear side cargo panel from the passenger's side, and plastic retaining pins from the lower battery floor covering. Set all removed items aside for reinstallation after the installation is complete.
Mount the lighting modules box in a clean, flat area near the driver's side taillight connector behind the side panel. Use the supplied double-sided tape with the epoxy pointing downward. The box must be positioned so that the connector with the green wire can be routed underneath the cargo hook mount toward the battery.
Locate and disconnect the vehicle's taillight wire harness connector on both driver's and passenger's sides, being careful not to damage locking tabs. Insert the connector with the yellow and red wires into the mating taillight and vehicle harness on the driver's side (Step 5). Repeat the connection on the passenger's side with the connector containing the green wire (Step 8).
Route the connector with the green wire underneath the cargo hook mount toward the battery. Route the green wire along the threshold to the passenger's side, underneath the passenger's side cargo hook mounting rails, and up and behind the passenger's side trim panel. Connect it to the passenger's side taillight.
Route the black 12 GA power wire and white 16 GA ground wire underneath the cargo hook mounting rail to the battery compartment in the center of the rear cargo area. Connect the white 16 GA ground wire to the negative side of the battery and the black 12 GA power wire to the positive side. Use a 10mm socket to connect the black lighting module power to the battery. Insert the 15-amp fuse into the fuse holder only after all other connections are complete.
Install the 15-amp fuse into the fuse holder only after all other installation steps are complete and the white ground wire is connected to the negative battery terminal and the black power wire is connected to the positive battery terminal. Do not insert the fuse before all connections are made.
Drilling may be required. The manual specifies a 3/32" drill bit in the tools list and notes that a 3/32" hole may be necessary to attach the white ground wire ring terminal to the vehicle body using the provided screw. However, the manual does not confirm whether an existing hole is typically available. Check your vehicle before drilling.
Before drilling, check for miscellaneous items that may be behind or under any surface to avoid personal injury or property damage. When passing the power wire through sheet metal, use an existing grommet, add a grommet, or use silicone to protect the power wire from sharp edges.
The battery connection must be fuse-protected with a maximum 15-amp fuse. The manual also notes that the fuse holder accepts a maximum 10-amp fuse in one reference. The 15-amp specification is stated as the maximum allowed. Exceeding the product rating can cause loss of warranty, overheating and potential fire.
Signal circuits are rated at 5.0 amps per side. Tail and running circuits are rated at 7.0 amps total. Do not exceed the product rating or the tow vehicle lamp load rating, whichever is lower.
The black power wire is 12 GA (gauge). The white ground wire is 16 GA. The power wire routed to the battery must be 12 GA or larger. Wire colors are: green for right turn, red for brake, yellow for left turn, and brown for taillight.
Green wire = right turn signal; red wire = brake signal; yellow wire = left turn signal; brown wire = taillight. These colors correspond to the standard trailer lighting functions and must be connected to the matching vehicle taillight circuits.
Yes. The manual specifies using a ring terminal for the battery connection. The white ground wire includes a ring terminal that must be attached to the vehicle body using the provided screw. The black power wire must also use a ring terminal (12-10 gauge) when connecting to the positive battery terminal.
When in use, route the 4-flat connector with the center of the vehicle and out of the hatch to the trailer, staying clear of the hatch's latching mechanism. When not in use, roll up and store in a convenient, out-of-the-way location. Install the provided 4-flat dust cover to help prevent corrosion.
The installation difficulty is rated as Difficult. Installation difficulty levels are based on time and effort involved and may vary depending on installer expertise, vehicle condition, and proper tools and equipment. Professional installation may be recommended.
Do not lay tools across the positive battery terminal (typically red covers or '+' symbol) as this can cause a ground short leading to sparks and electrical shocks. Isolate the negative battery cable after disconnection and ensure it does not touch metal objects. Do not exceed the product rating or tow vehicle lamp load rating. Check for items behind or under surfaces before drilling. Route the 12 GA power wire to avoid pinch points and hot or rotating components.
After ensuring the 15-amp fuse is installed and all connections are complete, verify that the harness is functioning by attaching the battery and testing with a test light, 4-flat tester, multimeter, or a functioning trailer. This confirms that all signal and power circuits are working correctly before towing.
Perform periodic inspection of all wires and connections to ensure there is no visible damage or loose connections. Secure any loose wires with the provided cable ties. Install the provided 4-flat dust cover to help prevent corrosion when the connector is not in use.
Curt 56557 is designed for SUVs and vans. Confirm your specific vehicle year, make and model with Curt or your retailer before purchasing, as the manual does not list compatible models.
Yes, you must disconnect the negative battery cable before installation and reconnect it only after all wiring is complete and the 15-amp fuse is installed.
Black power wire is 12 GA; white ground wire is 16 GA. Both must use ring terminals for battery connections.
Installation difficulty is rated as Difficult. Professional installation may be recommended depending on your expertise, vehicle condition and available tools.
After the 15-amp fuse is installed and all connections are complete, test the system by attaching the battery and using a test light, 4-flat tester, multimeter, or a functioning trailer to verify proper operation. This confirms that all signal circuits (left turn, right turn, brake) and tail/running circuits are working before towing.
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