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Originally Posted by stef
In europe you can find easily "tv-activator" wich can engage ou disengage the tv-security for most of the BMW production.
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This is very, cool. The only down side is that it is also very expensive too.
Here is the quick, overall answer. The TV module is a global part-- that is, it can be sold in any country of the world. Therefore, BMW must have the ability to configure the TV module to comply with a country's laws that require it to turn off when the vehicle is in motion. To solve this problem, BMW designed the TV module so that it can be "coded" (by a dealer or specialized mechanic with BMW's proprietary diagnostics computer) to turn off in motion or stay on.
The TV module knows the vehicles speed from a special speed message on the car's I-Bus. The I-Bus is like a computer network that is connected to many of the car's components, so you can not disconnect or short the I-Bus wire, otherwise the TV module would not work at all. Therefore, some smart inventors figured out a way to create a little computer module that connects to the I-Bus wire between the TV module and the rest of the car. That module lets all of the other signals through, but it blocks the vehicles speed signal from reaching the TV module.
The other approach to TV in motion is to re-code the TV module just to stay on. However, most dealers and mechanics will not override the regional coding on a TV module that would violate the law. So, that is pretty hard to accomplish. The cool tool that Stef points to looks like it can do the BMW re-coding through the car's OBD port. If so, that is most excellent. However, they cost six times as much as the in-line override modules that most folks (like EAS) sell.