DIY: How to Make Your Own ENET OBD2 Cable for BMW Coding and Diagnostics

For BMW enthusiasts and owners keen on delving into vehicle diagnostics, coding, and programming, the ENET (Ethernet to OBD2) cable is an indispensable tool. While purchasing one might seem straightforward, import restrictions or simply the desire for a hands-on approach can lead you down the DIY path. If you’re looking to connect your BMW to your laptop for advanced operations without breaking the bank or waiting for international shipping, creating your own Enet Obd2 Cable at home is a surprisingly accessible project. This guide will walk you through each step, allowing you to craft a reliable cable using readily available components.

Materials You’ll Need

Before we begin, gather these essential materials. You can easily find these items online, often from retailers like Amazon. Having everything ready will streamline the cable-making process.

1. Soldering Kit: Essential for securely connecting wires. A basic soldering kit will suffice for this project.
2. Multimeter: A multimeter is crucial for testing the resistor and ensuring correct connections.
3. Ethernet Cable (10 Feet): A standard Ethernet cable provides the necessary wiring. 10 feet offers a good balance of length and manageability.
4. OBD2 Connector (Male): This connector interfaces with your BMW’s OBD2 port. Ensure you get a male connector for making the cable.
5. 510 Ohm Resistor: This resistor is a critical component for the ENET cable’s functionality. Make sure it’s within the 506-560 Ohm range for optimal performance.
6. Cable Protector and Boot (Optional but Recommended): These provide strain relief and a professional finish to your DIY cable.

You might also find combo kits that include a soldering kit, multimeter, and cutter, which can be a cost-effective option if you’re missing multiple tools.

Step-by-Step Guide to Making Your ENET OBD2 Cable

Now, let’s get into the actual construction of your ENET OBD2 cable. Follow these steps carefully for a successful outcome.

Step 1: Prepare the Ethernet Cable

Begin by preparing the Ethernet cable.

1. Cut the Ethernet Cable: Cut the Ethernet cable approximately in half. This gives you two ends to work with, and you’ll be using one of these ends to create your ENET connector.
2. Insert Cable Protector and Boot (Optional): If you have a cable protector and boot, slide them onto the cut end of the Ethernet cable now. This will be placed over the OBD2 connector end later for a cleaner and more durable finish.
3. Strip the Outer Jacket: Carefully remove about 1-2 inches of the outer plastic jacket from the cut end of the Ethernet cable to expose the internal wires. Be cautious not to damage the insulation of the individual wires inside.

Step 2: Identify Ethernet Wire Colors and Tin the Wires

Understanding the Ethernet wire color coding is essential for correct pin assignments.

1. Identify Wire Colors: Examine the exposed wires. Standard Ethernet cables (using the T568B standard, which is common) have specific color pairings. You’ll see eight wires in total, often including: Orange, White/Orange, Green, White/Green, Blue, White/Blue, Brown, and White/Brown.
2. Tin the Wire Edges: Use your soldering iron to “tin” the exposed tips of each wire. This involves applying a small amount of solder to the wire strands. Tinning makes the wires easier to solder to the OBD2 connector pins and creates a stronger, more reliable connection.
3. Cut Unnecessary Wires: For this ENET OBD2 cable, you only need specific wires. The Blue, White/Blue, and White/Brown wires (typically associated with pins 4, 5, and 7 in some Ethernet configurations) are not required for this application. You can carefully cut these wires shorter to keep them out of the way.

Step 3: Prepare the OBD2 Connector

Now, let’s prepare the OBD2 connector to receive the Ethernet wires.

1. Open the OBD2 Connector: Carefully open the OBD2 connector housing. Most OBD2 connectors are designed to snap together, so you may need a small screwdriver or prying tool to gently separate the two halves.
2. Identify Pin Layout: Inside the OBD2 connector, you will see 16 pins arranged in two rows of 8. These pins are numbered from 1 to 16. Refer to an OBD2 pinout diagram if you are unsure of the numbering. Knowing the pin layout is crucial for correct wiring.

Step 4: Test the Resistor

The 510 Ohm resistor is a key component in the ENET cable circuit.

1. Test the Resistor with a Multimeter: Before soldering, use your multimeter to verify the resistance of the 510 Ohm resistor. Set your multimeter to measure resistance (Ohms – Ω). Place the multimeter probes on each lead of the resistor.
2. Verify Resistance Range: The reading should be close to 510 Ohms, ideally within the range of 506-560 Ohms. This tolerance ensures the cable will function correctly. Using a resistor outside this range might lead to communication issues.

Step 5: Soldering and Wiring – Connecting Ethernet to OBD2

This is the most critical step: soldering the Ethernet wires to the correct pins on the OBD2 connector and incorporating the resistor. Refer to the pinout diagram below for accurate connections.

1. ENET OBD2 Cable Pinout Diagram: Follow this wiring configuration precisely:

   Ethernet Pin #	Wire Color	OBD2 Pin #
   Pin 1	White/Orange	Pin 3
   Pin 2	Orange	Pin 11
   Pin 3	White/Green	Pin 12
   Pin 6	Green	Pin 13
   Pin 8	Brown	Pin 4 & 5

   • Pin 8 of Ethernet (Brown wire) goes to both Pin 4 and Pin 5 of the OBD2 connector. You will need to solder the Brown wire to a point where it can bridge and connect to both Pin 4 and Pin 5.

2. Solder Ethernet Wires to OBD2 Pins: Carefully solder each tinned Ethernet wire to its corresponding pin on the OBD2 connector according to the table above. Ensure each solder joint is clean and secure. Avoid creating solder bridges between adjacent pins.

3. Solder the 510 Ohm Resistor: The final wiring step is to solder the 510 Ohm resistor. Connect one lead of the resistor to OBD2 connector Pin 8 and the other lead to Pin 16. This resistor is crucial for proper communication in the ENET system.

Step 6: Final Assembly

With all the soldering complete, it’s time to assemble your DIY ENET OBD2 cable.

1. Close the OBD2 Connector Cover: Carefully close the OBD2 connector housing, ensuring that no wires are pinched or stressed. Snap the two halves of the connector firmly back together.
2. Slide Boot and Protector (Optional): If you used a cable boot and protector, slide them up the Ethernet cable and over the OBD2 connector end to cover the connection point for added protection and a more finished look.

Conclusion

Congratulations! You have now successfully crafted your own ENET OBD2 cable. This DIY cable provides a cost-effective and readily available solution for connecting your BMW to a laptop for coding, diagnostics, and programming. Connect your new ENET OBD2 cable to your BMW’s OBD2 port and the Ethernet port of your laptop. With the appropriate software, you can now begin exploring the advanced capabilities of your BMW, from reading diagnostic codes to performing custom coding modifications. Enjoy the power of DIY car diagnostics and coding with your homemade ENET OBD2 cable!