Databus Interface - How do they work.

Does anyone jnow how these databus interface modules work? I was curious if it was possible with enough knowledge to make your own.J Rilla

Owner/Installer

Could you post a bit more information? Where would one find these modules? Who makes them? Are they part of a particular make/model of car? Or aftermarket? DDR

Different ones work different ways. Some work on resistances other work on digital pulses with very specific timing between pusles. You will really have to find out specifics on the vehicle in question to be able to do this. IMO just buy the module needed and save the headaches.Certified Security Specialist

Always check info with a digital multimeter.

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k2thz check out www.bypasskit.com auex: Do they work as simple as that? I know that there is some use of resistor in cars today for doorlocks, parkinglights, etc., but I doubted the databus modules were that straight forward. If it is a matter if timed pulses then I dont think it would be worth trying, but if it is just resistors then it is really a piece of cake. I dont mind spending the money typically, but in order to get discounted prices, I need to buy in bulk, and thenI end up having a lot of inventory that I dont need. I just need to find a place in town that will sell them for cheap one at a time. Anyone else know more about them? J Rilla

Owner/Installer

"Does anyone jnow how these databus interface modules work?" I don't know, but I would guess someone gets a hold of the tech 2 or similar scan tools and sees what capabilities they have. They use the scan tool to test the locks and read what signal it sends to the databus? Like I said I really have no idea and wondered the same thing myself how someone goes about figuring that out..

For the most part they're huge time savers.  I would not stock all of them though, you don't need some of those to do basic functions such as lock, unlock, fact. disarm.  It's just an easy way to control a lot of options that aren't usually included with your basic alarm or R.S. install.  You don't need the one that bypasskit.com lists for the Jeep Liberty, it's just that almost everything is multiplexed needing resistors to interface certain functions.  Some of these they offer just as an easy, faster way to install.  I don't mind adding relays and resistors as long as it doesn't take a few more hours to do it.  The one I do stock is the GM Trailblazer, Envoy, Bravada interface. DEI part 455G, and 456G.  Don't even attempt to interface the doorlocks in those.  It takes way too long and is a real pain.  Also consider stocking the Jeep Grand Cherokee interface otherwise, you need 4 relays, 2 each in both front doors I believe for the locks.  You just have to let the customer know that their is no other way to do it with out the interface.  We only charge them for the part, nothing more for installing it, it's super easy to do anyways.  I wouldn't stock any of these in bulk, just have one or two around depending on how often you work on these type of vehicles.  We get ours direct from DEI, and they don't offer any bulk discount and are reasonably priced considering the time they save.  We also have a distributor that carries the same DEI interfaces thats just 1 ship day away so we're able to carry a low supply of them.  So I would only worry about the GM, and the Jeep Grand Cherokee interfaces. Thats all we stock.  I hope this helps you out.

To bad they cannot move them to the next level and interface with the engine computer for security. I've had a Tech 2 in my truck and the guy starting shutting down injectors and what not. It was so cool. It would be great to introduce this into the carjacking system. Activate the carjacking feature and the car would run like crap making it useless but keeping power to the steering and vaccum to the brakes for safety. Heck, why bother with starter kill. They could just kill the passlock/pats systems.

Ok so Take the Jeep Liberty for example: Is it posible to just make all of the connections to the data line as long as I use the proper resistor? The door locks, parking lights and factory diarm are all (-) through different value resistors, so it would seem to me that it could work.J Rilla

Owner/Installer

Well like I mentioned about reading what signals a tech 2 sends, I assume you could do the same with the bypass..Just hook the bypass up and then try the system and see what signals it throws when using the system. Might not want to have the bypass hooked to the data wire in the car though since then trying to read off of it might add some resistance I don't know how tight the tolerances are..