After the seeing the concerns across at least 4 different threads about the recent rash of thefts of our beloved cars, I thought I'd start documenting the efforts of myself and my friend "J". J is a former professional audio/alarm installer who now works in IT, and I know professionally. He deserves the credit for this design and honestly did most of the research, editing, and documentation. He's not a member of this forum but I'm grateful for his help and I couldn't have done this without him.
We wanted to create a DIY implementation with some inexpensive parts, and provide detailed instructions that would allow a non-expert competent DIY person to follow. I think the total cost is under $100 assuming you have all the required tools. Everything is available for purchase on Amazon.
We placed 10k resistors between the Data1+ and Data1- dummy OBD pins. likewise the Data2 pins. This also an optional step to the implementation.
Thanks to
Keep_hope_alive for this suggestion:
"The intent of the 10k ohm resistors, one from each data pin to associated signal ground, is to make the reader think there is a circuit but it won't understand why it doesn't read any data. It prevents errors from an open circuit. The 10k ohm size ensures that nothing is damaged and is close to the input resistance of the actual circuit."
So, we fake the ECU circuit with the 10k resistors. The cloning tool sends out 2-5VDC, and establishes OSI layer 2 connectivity (with itself) for a serial connection. L3 and above obviously will not work, but this serves as another layer of obfuscation to confuse a thief into believing the dummy port may be operational.
Additionally, I recommend putting a cheap (3D printed) OBD2 lock on your dummy cable. It will help convince/distract a thief that the port was worth protecting, slow them down, and any damage done removing the lock will be on the dummy port.
With the relay boards in "MODE 12", once triggered, they will keep a persistent output condition even when the offending OBD reader is removed, until either the timers elapse or the reset button is pressed. If everything in this system were ripped out, the car will not start. With everything in place, the car will start and remote start should still work. The relay boards have a lower power mode with nothing displayed and have a non-volitile memory if they lose continuous power, they should resume operating how they were last configured.
Here's a
demo video of the final operating model on a bench:
We included two independent timer relays to control the starter lockout and the siren duration. You could do the project with a single timer relay board, with the same duration applied to the siren and the starter lockout.
Tools:
Wire stripper,
crimper,
multimeter,
12VDC source (old battery for bench testing),
soldering iron,
butane lighter,
pin removal tool (optional),
Ferrule crimper (optional).
Materials: Multiple colors of wire, at least red and black. 16-18 AWG is more than adequate.
Ferrule crimps (optional).
Solder melt butt connectors.
Wago clips (optional),
10k Ohm resistors,
5A blade fuses
shrink tubing.
Parts:
2X Timer boards
Posi-Tap connectors
OBD2 Pigtail
Momentary Reset Switch
5 Pin Relay Harness (optional, only need one)
Mini Piezo Siren
Fused distro block
5 pin relay 5pin single pole double throw Waterproof to handle any kind of moisture that might or might not hit it 40amp capable
That's all I can provide for now, more videos and drawings will follow. Feel free to ask questions and hopefully someone else will benefit from this.