For car enthusiasts and those who rely on OBD2 devices for various functionalities, the limitation of a single OBD2 port can be a real inconvenience. Many modern drivers want to use multiple OBD2 devices simultaneously—perhaps a radar detector for safety and a performance monitor for tracking vehicle data. The problem arises: how do you connect two OBD2 devices to a single port? This guide will walk you through a DIY solution to use two OBD2 devices in your car by utilizing an OBD2 splitter and a selector switch, ensuring you don’t have to choose between your favorite gadgets.
Understanding the Challenge of Multiple OBD2 Devices
The standard OBD2 port in your vehicle is designed to communicate with one device at a time. While OBD2 splitters are available, simply plugging in two devices often leads to conflicts. Typically, both devices will attempt to connect, resulting in one device interrupting the other’s connection, making simultaneous and reliable data access impossible. This “device A connects, then device B, then back to A” cycle renders the splitter ineffective for running two devices concurrently.
For instance, you might want to permanently install a radar detector that uses an OBD2 connection for features like speed-sensitive muting, and also regularly use a WiFi OBD2 adapter for performance monitoring or diagnostics with your smartphone. Unplugging and replugging devices becomes tedious and impractical.
The DIY Solution: OBD2 Splitter and Selector Switch
A more effective approach involves modifying an OBD2 splitter cable with a Single Pole Double Throw (SPDT) switch. This switch will act as a power selector, allowing you to choose which of the two OBD2 devices receives power from the car’s OBD2 port. Since power is supplied through pin 16 of the OBD2 port, interrupting the power supply to one device effectively deactivates it, allowing the other to communicate without conflict.
This method ensures that only one device is actively drawing power and attempting to communicate at any given time, resolving the connection conflicts inherent in basic splitter setups. This DIY modification is relatively straightforward for anyone with basic automotive electrical knowledge and some simple tools.
Step-by-Step Guide: Installing the OBD2 Switch
Here’s how to set up your OBD2 switch:
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Acquire the necessary components:
- OBD2 Splitter Cable (Male to Dual Female)
- SPDT Switch
- Automotive Wire (Solid Core, slightly heavier gauge)
- Electrical Tape
- Solder and Soldering Iron
- Wire Strippers/Cutters
- Voltmeter
- Dremel or Rotary Tool (optional, for cubby modification)
- Drill (with 1/2″ drill bit)
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Identify Pin 16 (Power Wire): Carefully cut open a section of the OBD2 splitter cable to access the internal wires. Using a voltmeter, identify pin 16 on the male end of the splitter. The original author noted that on their eBay splitter, pin 16 corresponded to a green wire with a white stripe. Verify this on your cable, as wire colors can vary.
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Cut and Prepare Pin 16 Wires: Once identified, carefully cut the pin 16 wire on both female ends of the splitter cable. Strip the ends of the cut wires to prepare them for soldering.
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Install the SPDT Switch: Solder the heavier gauge wires to the ends of the cut pin 16 wires. Connect the other ends of these new wires to the terminals of the SPDT switch. The switch will now control the power flow to each of the female OBD2 connectors. Use electrical tape to re-insulate any exposed wires and to secure the modifications to the splitter cable.
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Conceal the Installation (Optional): For a clean and hidden setup, consider mounting the switch in an inconspicuous location like a glove box or dashboard cubby. The author chose the storage cubby to the left of the steering wheel in their BMW F30. This involves removing the cubby, drilling a hole for the switch, and routing the OBD2 cable through another hole.
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Final Assembly and Testing: Connect your OBD2 devices to the female ends of the modified splitter. Mount the switch in your chosen location. Test the setup by toggling the switch and verifying that only the selected OBD2 device is active at any time.
Benefits of Using an OBD2 Switch
This DIY OBD2 switch provides a practical and cost-effective solution for using multiple OBD2 devices without the hassle of constant swapping or the unreliability of basic splitters. It offers:
- Convenience: Easily switch between devices with a flip of a switch.
- Flexibility: Use different OBD2 devices as needed without physical reconnection each time.
- Clean Setup: With hidden switch and wiring, the modification can be virtually invisible.
By implementing this simple modification, you can seamlessly integrate multiple OBD2 devices into your vehicle, enhancing both your driving experience and vehicle diagnostics capabilities.
