Connecting your BMW to a laptop for diagnostics and coding often requires a specialized Obd Ethernet cable. While commercially available, building your own OBD ethernet cable can be a cost-effective solution. This guide provides a step-by-step walkthrough for creating a DIY OBD ethernet cable compatible with BMW vehicles.
This project offers a hands-on approach to understanding the connection between your vehicle’s onboard diagnostics system and your computer. By constructing the cable yourself, you’ll gain valuable insight into the communication protocols used for diagnostics and coding. This DIY solution allows for customization and ensures you have the right tool for the job. Let’s get started!
Building Your OBD Ethernet Cable: A Step-by-Step Guide
Before starting, gather the necessary components: a soldering kit, a multimeter, a 10-foot ethernet cable, an OBD2 connector, a 510 Ohm resistor, wire cutters, and a cable protector and boot. Optionally, a combined soldering kit and multimeter with cutters can simplify the process.
Step 1: Preparing the Ethernet Cable
Begin by cutting the 10-foot ethernet cable in half. Install the cable protector and boot onto the cut end that will connect to the OBD2 connector to provide strain relief and a professional finish.
Step 2: Exposing and Identifying the Wires
Carefully remove the outer plastic layer of the ethernet cable, exposing the internal twisted pairs of wires. Refer to a standard T568B wiring diagram to identify each wire by its color code. This step is crucial for ensuring correct connections later. Tin the exposed ends of each wire using the soldering iron to prepare them for soldering. You can trim and discard the blue, white/blue, and white/brown wires (pins 4, 5, and 7) as they are not required for this project.
Step 3: Examining the OBD2 Connector
Open the OBD2 connector housing to expose the 16 pins arranged in two rows. Familiarize yourself with the pin numbering, typically numbered 1 through 16 from left to right and top to bottom.
Step 4: Verifying the Resistor
Using the multimeter, test the 510 Ohm resistor to confirm its resistance is within the acceptable range of 506-560 Ohms. This resistor plays a critical role in ensuring proper communication between your laptop and the vehicle.
Step 5: Soldering the Connections
Following the pinout diagram below, carefully solder each ethernet wire to the corresponding pin on the OBD2 connector. Double-check each connection to ensure accuracy.
Ethernet Pin to OBD2 Pin Connections:
- Pin 1 (White/Orange) to OBD2 Pin 3
- Pin 2 (Orange) to OBD2 Pin 11
- Pin 3 (White/Green) to OBD2 Pin 12
- Pin 6 (Green) to OBD2 Pin 13
- Pin 8 (Brown) to OBD2 Pins 4 & 5
Finally, solder the 510 Ohm resistor across pins 8 and 16 of the OBD2 connector. This completes the wiring process.
Step 6: Final Assembly
Close the OBD2 connector housing securely, ensuring all connections are protected. Your DIY OBD ethernet cable is now complete.
Conclusion
By following these steps, you can successfully create your own OBD ethernet cable for BMW diagnostics and coding. This cable will allow you to connect your laptop to your vehicle, enabling you to perform various tasks such as reading and clearing fault codes, monitoring live data, and customizing vehicle settings. Always double check your connections before connecting to your vehicle.
