For automotive enthusiasts and DIY mechanics, having the right tools for diagnostics is crucial. The OBD2 (On-Board Diagnostics II) port in your vehicle is your gateway to understanding its health, and a reliable OBD2 cable is essential for connecting diagnostic tools. While pre-made cables are readily available, building your own 16 pin OBD2 cable offers customization and a deeper understanding of the connections involved. This guide provides a step-by-step approach to creating a custom OBD2 cable, focusing on durability and the importance of 16 Pin Obd2 Cable Bend Radius for long-term reliability.
Understanding the Essentials: Tools and Parts
Before diving into the build process, let’s gather the necessary tools and parts. Remember, this is a DIY project, and while it’s designed to be straightforward, proceed with caution and at your own risk. Incorrect wiring can potentially damage your vehicle’s ECU or diagnostic equipment.
Tools You’ll Need:
- Wire strippers/cutters: For preparing the wires by removing insulation and cutting them to length.
- Needle-nose pliers: Helpful for manipulating small components and crimping in tight spaces.
- Molex crimping tool (recommended): While not strictly required, a crimping tool ensures a secure and professional connection of the pins to the wires, enhancing durability and electrical conductivity.
- Soldering iron (recommended): Soldering provides a robust and electrically sound connection, especially beneficial for smaller gauge wires. It adds an extra layer of security against wire pull-out and corrosion.
Parts Required:
- 4-pin connector: This connector will interface with your specific diagnostic tool or adapter. Ensure it’s compatible with your intended application. (Link to part used; pin/wire size = 22-16AWG; insulation/seal size = 1.3-1.7mm)
- OBD-II Cable: This is the core component providing the 16 pin OBD2 connector. Consider the bend radius of the cable when selecting one. A cable with a good bend radius will be more flexible and less prone to damage from bending, especially in tight engine compartments. (Link to part used)
For budget-conscious builders, you can utilize spare wires you might have on hand. In this case, you’ll only need to purchase the female OBD-II connector and run individual wires to your 4-pin connector. However, ensure you know the wire gauge you’re using to select the correct 4-pin connector and pins for proper fit and secure connections.
Pin Configuration: Focusing on the Essential 4 Wires
The 16-pin OBD2 connector houses numerous pins for various diagnostic and communication protocols. However, for many basic diagnostic applications, only four pins are essential. Our focus will be on these four key connections within the OBD-II cable (referred to as OBD2C):
- Pin 4 (Chassis ground): Provides the ground reference for the electrical circuit (Orange wire on the specified OBD2C).
- Pin 6 (CAN [J-2234] High): Carries the CAN (Controller Area Network) high signal for communication (Green wire on the specified OBD2C).
- Pin 14 (CAN [J-2234] Low): Carries the CAN low signal, completing the CAN communication circuit (Brown w/white stripe wire on the specified OBD2C).
- Pin 16 (Battery power): Supplies power to the diagnostic tool via the OBD2 port (Green w/white stripe wire on the specified OBD2C).
Understanding these pin assignments is crucial for correct wiring and ensuring your custom cable functions as intended.
Understanding the OBD2 connector pinout is essential for correctly wiring your custom cable.
Step-by-Step Guide to Building Your Custom OBD2 Cable
Now, let’s proceed with the step-by-step construction of your custom 16 pin OBD2 cable.
Step 1: Preparing the OBD2 Cable Wires
Begin by preparing the OBD2 cable. Carefully remove the outer sheath and shielding from the OBD2C to expose the internal wires. Identify the four wires corresponding to pins 4, 6, 14, and 16 as listed above. Separate these four wires from the remaining twelve, which are not needed for this basic setup. Bundle the unused wires and secure them neatly with a zip-tie to keep them out of the way and prevent accidental shorts or interference.
Removing the outer sheath and shielding to access the necessary wires within the OBD2 cable.
Isolating the four essential wires needed for building the custom OBD2 cable harness.
Step 2: Preparing the Wire Ends for the 4-Pin Connector
The wires within the specified OBD2C are 26AWG, which is slightly smaller than the 22AWG wire size that the pins of the 4-pin connector (4PC) are ideally designed for. To compensate for this difference and ensure a secure connection, we’ll “thicken” the wire ends.
The wires come pre-stripped with a short length of exposed conductor (around 1/8″). Strip off approximately 3/8″ of insulation from the end of each of the four selected wires. Fold the exposed wire strands back over themselves, effectively doubling the wire thickness. Twist the folded strands tightly to create a more substantial wire end that will fit snugly within the 4PC pins. Slide a rubber seal (included with the 4PC kit) onto each wire, ensuring it’s positioned before the wire end to seal the connection later.
Preparing the wire ends by stripping, folding, and twisting to increase thickness for a better fit with the connector pins. Rubber seals are also positioned on the wires.
Step 3: Attaching Pins to the Wire Ends
Now, take the pins from the 4PC kit. Each pin has two sets of prongs. The front prongs are designed to crimp onto the exposed wire, while the rear prongs crimp onto the wire insulation/seal. Insert the prepared wire end into the front of the pin, ensuring the exposed wire aligns with the front prongs. Due to the small gauge of the wire relative to the pin size, using needle-nose pliers to hold the wire in place during the next step is highly recommended. This will help maintain alignment and ensure a proper connection.
A close-up view highlighting the small gauge of the wire compared to the size of the connector pin before soldering.
Step 4: Soldering the Wires to the Pins (Recommended)
Soldering the wire to the pin connector is highly recommended for a robust and reliable connection. Solder provides superior electrical conductivity and mechanical strength compared to crimping alone, especially with smaller gauge wires. If you choose to solder, apply a small amount of solder to the area where the wire strands meet the pin’s front prongs. Ensure the solder flows smoothly and creates a solid bond. If you are new to soldering, numerous online resources, such as the linked YouTube video in the original article, can provide helpful tips and techniques.
Soldering the wire to the connector pin to ensure a strong and electrically conductive connection.
Step 5: Crimping the Front Prongs (Alternative to Soldering or for Added Security)
If you prefer crimping or want to add extra security to a soldered connection, use a Molex crimping tool to crimp the front prongs of the pin connector around the exposed wire. If you don’t have a crimping tool, needle-nose pliers can be used as a substitute. Carefully and gradually fold each prong over the wire, ensuring a tight crimp. Numerous online videos demonstrate proper crimping techniques using pliers if you are unfamiliar with the process (like the YouTube video linked in the original article). For added measure, you can use pliers to further flatten the crimped prongs for an even more secure connection.
Crimping the connector pin around the wire using pliers as an alternative to a dedicated crimping tool.
A detailed view of the connector pin after the front prongs have been crimped securely around the wire.
Step 6: Crimping the Rear Prongs over the Seal
Slide the rubber seal up the wire until it sits between the rear prongs of the connector pin. Using the same crimping technique as before (either with a crimping tool or needle-nose pliers), fold the rear prongs over the rubber seal. This crimp provides strain relief and environmental protection, securing the seal in place and preventing moisture or contaminants from entering the connection.
Positioning the rubber seal correctly before crimping the rear prongs of the connector pin.
Crimping the rear prongs of the connector pin to secure the rubber seal and provide strain relief.
A completed connector pin showing both front prongs crimped around the wire and rear prongs crimped around the rubber seal.
Step 7: Wire Pairing (Recommended for Signal Integrity)
While not strictly mandatory for basic functionality, twisting pairs of wires is often recommended in data communication applications like CAN bus systems to minimize electromagnetic interference and improve signal integrity. Pair and twist the wires as follows:
- Pair 1: Pin 4 (orange) and Pin 16 (green w/white stripe) – Power and Ground pair.
- Pair 2: Pin 6 (green) and Pin 14 (brown w/white stripe) – CAN High and CAN Low pair.
Twist each pair of wires together along their length. This technique helps reduce signal noise and ensures more reliable data transmission, particularly important for accurate diagnostic readings.
Step 8: Inserting Pins into the 4-Pin Connector Housing
Finally, insert the completed pins into the 4-pin connector housing (4PC) in the correct orientation. Refer to the following pin assignments and the image below for correct placement:
- Connector Slot A: Pin 14 (brown w/white stripe) – CAN Low
- Connector Slot B: Pin 6 (green) – CAN High
- Connector Slot C: Pin 16 (green w/white stripe) – Battery Power
- Connector Slot D: Pin 4 (orange) – Chassis Ground
Insert each pin into the rear of the connector housing until it clicks audibly into place, indicating it is securely locked. Using needle-nose pliers to gently pull on the wire from the rear can help ensure the pin is fully seated and locked.
Diagram illustrating the correct pin insertion order and positions within the 4-pin connector housing.
Conclusion: Your Custom OBD2 Cable is Ready
Congratulations! You have successfully built your own custom 16 pin OBD2 cable.
The completed custom 16 pin OBD2 cable, ready for use.
The custom-built OBD2 cable connected and ready for diagnostic use.
This custom cable can now be used to connect your diagnostic tools to your vehicle’s OBD2 port. It’s always a good practice to test your newly built cable to ensure it functions correctly. In the original article, the builder successfully used their cable to check and clear a self-induced error code.
Confirmation of successful testing and use of the custom OBD2 cable for diagnostics.
Remember, paying attention to details like wire preparation, secure connections (soldering and crimping), and considering the 16 pin OBD2 cable bend radius during cable selection will contribute to the durability and reliability of your custom OBD2 cable. This DIY project not only saves potentially money but also provides a valuable learning experience and a customized tool for your automotive diagnostic needs.
