Wow, I just had a flashback to the mid '80's when we were testing engine control modules at Motorola's Automotive Division is south Texas which caused me to do some web surfing (I know, dangerous thought). I agree with the following comment I found on another forum discussing how companies are using the CAN bus to monitor the obvious, that a bulb has gone out and don't see why you can't put a bulb designed to support a bus that doesn't exist in the truck.
Am I missing something?
"At least in the modern vehicles I'm the most familiar with, the CAN bus, if it has one, has nothing to do with monitoring the status of any of the light bulbs in the car. Individual sensors are unlikely to be tied directly into the CAN bus of a vehicle. This is because, for something to be tied into the CAN bus, it has to have the ability to communicate on the CAN bus. It's expensive to give each and every sensor the necessary communication hardware to send and receive CAN messages.
In reality, most sensors report directly back to a module through any number of electrical signals (not CAN messages). From there, the module either acts directly on the signal, or if necessary, converts that sensor's reading into a network message and sends it over the CAN bus to another module.
In the case of light bulbs on a car, they're generally all controlled by just a very few modules, maybe just one. And, if the current through the bulb is actively monitored, it's monitored directly by that module, the same module providing power to the bulb. This is where my knowledge gets spotty, but I believe the output for any bulb that's actively monitored for current flow has a FET transistor on the output circuit to the bulb, and somehow this provides a signal back to the module indicating the current flow through the bulb. So, when you say that the sensor is further back in the wiring harness, that's pretty much correct. It's all the way back directly inside the module that's putting voltage out to the bulb.
Anyway, what it all boils down to is that the same module powering your bulbs is the one that's monitoring them for faults, no CAN bus involved. And furthermore, there's not much of a reason for any module in the vehicle to give a damn about what current your dome light is drawing aside from the module actually powering the dome lamp. So, the current draw of your dome lamp is never going to be encoded into a CAN message and sent over CAN bus, because no one else cares how your dome lamp is doing. (Well, ok, that module might send out a general CAN message saying "dome lamp burned out" so the cluster will display a message for you telling you it's burned out, but that's about it.)
So please, let's all stop calling it a CAN bus bulb. It's a ridiculous term, and it's making my head hurt."