[The Maverick]

Interested to hear a test of the rear fuse box info - that would be a great combo with the various other options...

[DamonZ28]

I plugged in my OBD reader with the fuse installed, and it powered up & communicated with the car, even without the ignition turned on. I simply opened the car door (with my fob in my pocket), pulled my OBD port out of the dash, unplugged my AFM disabler, and plugged in my OBD reader. I pulled the fuse (it's a 10A) and the OBD port did not have any power, and the OBD reader did not power on. It didn't throw any codes. Seems like this might be a good free option if you're parking in an area that you're unfamiliar with, or a potentially unsafe area.

[DamonZ28]

Originally Posted by SpeZ

not sure right now what fuse it is. Probably a 15A.
Using a car battery and connecting + and - at each side of the fuse is enough to blow the fuse instantly.
(wouldnt do it with the used car battery in the trunk, or atleast completly disconnect before)

I have a marine battery in my garage, unhooked for winter storage. That should do it. Thanks.

Originally Posted by SpeZ

I am really not sure how the thiefs use the OBD tho...
They break into the car plug the OBD in and program a new key. Does the OBD provide electricity even without ignition or do they use external power in order to access the modules?
If the OBD got no power with ignition on then they use external power, a broken fuse wont help for sure. Otherwise this would be an insanely good theft prevention without any costs.

See my post above. The ignition doesn't even need to be switched on for the OBD to have power. It must have constant power, because my OBD reader powered up without even touching the ignition switch. But removing the fuse completely removes power from the OBD port, even when the car is started (which I tried). The car starts just fine with the OBD fuse removed, and the only message on the DIC was that the trunk was open.

[SpeZ]

Originally Posted by DamonZ28

But removing the fuse completely removes power from the OBD port, even when the car is started (which I tried). The car starts just fine with the OBD fuse removed, and the only message on the DIC was that the trunk was open.

Awesome, thanks for trying it out since I am not at home.
But I will definetly plug there a blown fuse in.
Thieves won't have enough time to check fuses, they probably think the OBD is just broken or disconnected and leave.
Another security adder might be to disable the open trunk button in the door, unless they can unlock the trunk from the inside with the buttons near the door handle. Maybe these do only unlock the driver and passenger door. So that the only way to unlock the trunk to reach the fuse would be to sneak from the rear seat into the trunk in order to pull the emergency latch.

[Deacon Blues]

Great stuff! Thanks for figuring this out.

[SS_Don]

Ordered Mobilistics today.

[weekend_cruiser]

Originally Posted by DamonZ28

I plugged in my OBD reader with the fuse installed, and it powered up & communicated with the car, even without the ignition turned on. I simply opened the car door (with my fob in my pocket), pulled my OBD port out of the dash, unplugged my AFM disabler, and plugged in my OBD reader. I pulled the fuse (it's a 10A) and the OBD port did not have any power, and the OBD reader did not power on. It didn't throw any codes. Seems like this might be a good free option if you're parking in an area that you're unfamiliar with, or a potentially unsafe area.

FYI, the OBD device they are using might be self powered. OBD devices either get their power from the OBD port or the OBD device will provide it's own power. The power from the OBD port is vehicle battery connected and not switched. Usually advanced or fancy OBD devices that tend to draw a lot of current will provide their own power.

Maybe also test with a self-powered OBD device to ensure there is no data communication with the vehicle with fuse pulled. I could be wrong but I don't think the fuse kills the data communication. Some of us are disconnecting the CAN data wires from the OBD port as a safety measure and leaving the power wires connected. There is a thread on this.

[SpeZ]

Originally Posted by weekend_cruiser

FYI, the OBD device they are using might be self powered. OBD devices either get their power from the OBD port or the OBD device will provide it's own power. The power from the OBD port is vehicle battery connected and not switched. Usually advanced or fancy OBD devices that tend to draw a lot of current will provide their own power.

Maybe also test with a self-powered OBD device to ensure there is no data communication with the vehicle with fuse pulled. I could be wrong but I don't think the fuse kills the data communication. Some of us are disconnecting the CAN data wires from the OBD port as a safety measure and leaving the power wires connected. There is a thread on this.

I have checked the wiring now. The fuse kills the electricity straight from the battery.
In the OBD connection Slot 16 will be without power.

Usually OBD connectors grab their power from there in order to work.
OBD plugs are commonly connected with a laptop through USB (just like HPTuners).
USB can only deliver 5 volts, this is pretty sure not enough to power and access the car modules.
Of course they could add additional wires to externally power it with 12 volts, but makes the stealing device more complicated.

Funny thing would be to install a dummy OBD which works exactly like those USB Killers, which instantly kills devices when plugged into.


At the end it's a small trick for no costs and should be combined with other theft preventions.

[weekend_cruiser]

Originally Posted by SpeZ

I have checked the wiring now. The fuse kills the electricity straight from the battery.
In the OBD connection Slot 16 will be without power.

Usually OBD connectors grab their power from there in order to work.
OBD plugs are commonly connected with a laptop through USB (just like HPTuners).
USB can only deliver 5 volts, this is pretty sure not enough to power and access the car modules.
Of course they could add additional wires to externally power it with 12 volts, but makes the stealing device more complicated.

Funny thing would be to install a dummy OBD which works exactly like those USB Killers, which instantly kills devices when plugged into.


At the end it's a small trick for no costs and should be combined with other theft preventions.

I am with you on layering multiple theft preventions .

I however wanted to provide some insight to those who use the OBD fuse method so they have a good understanding of what protection they do or don't have. The CAN bus that the OBD devices use to communicate with the vehicle doesn't operate at 12V, it's between 1V-4V. I don't think self-powered OBD devices use the 12V from the port (but could be wrong). No one should take my word for it though (I am just a random guy on the internet ). Those who are interested should google how the CAN physical layer works and also look at the CANH/L operating conditions of automotive CAN transceivers and decide for themselves.

I am not telling anyone how they should protect their own vehicle but point I am trying to make through this is that OBD-wise, what is more important to disconnect is the data wires and not the power. Cheers.

Btw, I wouldn't recommend OBD port killer though . You might kill friendly OBD devices like from the dealer and they will probably be very unhappy with you.

[The Maverick]

I can also confirm that the ODB port has power with the ignition off -- it powers up my Autel code reader when I just open the door and plug it in. But I haven't had a chance to test the OBD fuse pull against port-powered versus self-powered devices.

Mounting one of those universal fuse bypass switches in an inconspicuous spot in the trunk would be a convenient way to implement the fuse pull. However, as noted in the prior post, the usefulness of that comes down to whether that approach actually impacts the type of devices that are typically used in the OBD thefts.

[SpeZ]

Originally Posted by weekend_cruiser

The CAN bus that the OBD devices use to communicate with the vehicle doesn't operate at 12V, it's between 1V-4V. I don't think self-powered OBD devices use the 12V from the port (but could be wrong).

Exactly, the communication cables operate with less than 4,5V.
"Terminal 16: Scan tool power, battery positive voltage terminal" In the wiring diagram it also gets powered directly by the 12V battery.

[The Maverick]

Originally Posted by The Maverick

This OBD lock is selling for $24. It is a 3D-printer product, but it seems adequate for my purposes so far:

https://www.amazon.com/dp/B0BTW92ZPS...language=en-US

It also allows some front to back movement, so I was thinking about inserting a thin plastic shim to see if I can eliminate the slack.

An update on this 3D-printed OBD port lock that I have been using. I've made two changes to try and improve the effectiveness.

I am using this on an OBD splitter cable. This lock latches onto a nub on the bottom of the OBD connector. That nub had an angled ramp (circled in photo below) that I think makes it easier to pry off the OBD lock. So I cut that angled ramp off the nub so the lock has a flat surface to grab against (arrow points to the modified nub).



I also added a flat plastic shim inside the lock to eliminate the front to back slack. An appropriate (or inappropriate?) level of brute force will likely still be able to remove the lock, but that just leads to another set of "problems" for the would be thief. TBD.



Finally, I have the following splitter coming for possible use. With my OBD port appearing disabled, someone looking under the dash will see three bright yellow connectors hanging down in various places. Maybe they will have 12V... maybe they will fry a device hooked up to them... or maybe they will be connected to a salvaged ECU that the thief's OBD device can try to talk to. Options!

[weekend_cruiser]

Originally Posted by The Maverick

Finally, I have the following splitter coming for possible use. With my OBD port appearing disabled, someone looking under the dash will see three bright yellow connectors hanging down in various places. Maybe they will have 12V... maybe they will fry a device hooked up to them... or maybe they will be connected to a salvaged ECU that the thief's OBD device can try to talk to. Options!

Hahahaha, that's genius.

[DamonZ28]

I talked with my cousin today, who has a huge auto shop class in a high school that looks nicer than most shops. He has several scan tools in his shop. He can use a powered scan tool (Snap On or others) to communicate with the car even if the OBD fuse has been removed. So unless the thieves aren't using a powered device, removing the fuse won't do much good. :(