To start, detach the sticker from your ELM327 cable enclosure and use a small star screwdriver to remove the four screws.
Next, carefully slide out the internal circuit board from the enclosure.
Pro Tip: Before disconnecting any internal connectors, use nail polish to mark one side of the connector that links to the OBD2 port. This helps in reassembly, though it’s generally not necessary for this guide.
Now, solder two wires to the TX (Transmit) and RX (Receive) pins on the circuit board. The provided images detail the pin-out for the USB Bridge chip, which will guide you. Exercise caution during soldering, as delicate components can be easily desoldered. If this happens, as in my case, and you can’t reattach them, there’s still a chance it might function correctly afterward.
Helpful Hint: To locate the TX pin, program your Arduino to send serial data to the serial monitor with short intervals. Connect a jumper wire to the Arduino’s TX pin and gently probe the ELM327 board. Observe for serial activity, indicated by flickering surface-mounted LEDs, which confirms communication. Unfortunately, this method is less effective for the RX side, but the provided photos clearly show the soldering points.
Important Note: The USB cable connects to the board via a 4-pin connector. To prevent the ELM327 from attempting to communicate with a PC while connected and ensure Arduino communication, sever the middle two pins of this connector. This modification allows the ELM327 to draw power from a PC USB port without engaging its serial controller, thus freeing it for Arduino communication.
Once the modifications are complete, rehouse the board in its enclosure. For my setup in my Jeep, the bulky enclosure was obstructive, so I simply used tape for a temporary seal. The original enclosure will be repurposed for another project.
