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June 27, 2016

OBD-II Break-Out Box (DIY Edition)

Written by Jason Ashton
Penetration Testing Security Testing & Analysis
When assessing a vehicle's various electronic systems, the primary interface is the On-Board Diagnostics (OBD-II) port. This provides the connection to interface with the vehicle's CANBus, among others. The CANBus has been utilized in vehicles within the US since the 90s and has been mandatory since 2008. While the CANBus, +12VDC, and Ground pins are in standard locations on the connector, other connection points like K-Line and manufacturer specific protocols can vary. Additionally, the two most common CANBus to computer interfaces, USB2CAN and Cantact, also utilize differing pins on their respective DB9 connectors to interface with the CANBus pins on the OBD-II port.

OBD-II Pin-out

Enter the OBD-II break-out box. This device splits each of the OBD-II pins to a female banana jack, allowing for individual connection to each signal. An OBD-II fan-out cable can then be used to re-arrange the connections back to a male OBD-II connector for connection to a vehicle or CANBus communication interface. Break-out boxes tend to be fairly expensive, with the most common ranging from $150 to $250 USD.

Typical Break-out Box

With some basic skills, tools, and materials we can build one of equal or better quality for around $31.00 to $42.00 USD, depending on what type of banana jacks you prefer. Note that I already had the pin crimper for the OBD-II connector, heat shrink tubing, cable grommet, and vinyl to print the label. So those may be additional costs. The materials list used for this build are as follows: Panel Mount Banana Jack**: Project Box: OBD-II Extension Cable: Panel Mount OBD-II Cable: **at the time of the build, black was available Be advised that the panel mount banana jacks referenced above are nickel plated (not noted in the product specifications). This interferes with getting the solder to flow prior to the plastic housing melting. A carbide stone bit in a Dremel tool to remove the plating from the solder cup alleviated this issue. Cutting off the female end of the OBD-II extension cable and prepping for the box, the conductor color is as follows (you should confirm for your exact cable). A length of this cable was used to build the OBD-II connector for the box. Images of the assembled product are included below. Also included are .PDF drill templates and label for the box top/connections. As shown in the images, the box lid will be the bottom of the box to allow it to be removed once the label is applied.

Box Inside

Box OBD-II Output Connector

Box Top

Additional materials are located here: