I didn't see in the manual a bulb failure warning light, isn't that a trait that they are canbus controlled if there is a failure warning light?
No, light failures can be monitored without a CAN bus, regardless of LED or bulb.
For bulbs you have three simple ways to monitor them which can be done by a relay (even simple electro-mechanical ones) or simple electronic devices. For turning indicator bulbs there is even a fourth method available. They base on load or pulses. However, no CAN bus is needed.
When we talk about LED one if these methods is not possible. That is the measurement of high current when the bulb is switched on (as the conductor is cold). That is not possible with LED, as it has not a peak current when it is switched on. This method is for turning indicators only, as they permanently turn on (get heated) and off (cool down). For lights which stay on you wouldn't see when they break later if you use this method.
For "dumb" LED lights where one LED is used or where you're not legally required to monitor them you simply can use two of the remaining methods to check if it is still working, both based on load. As I said, these can even be done by electro-mechanical devices, as it is done for turning indicators since decades.....
For LED turning lights either two of the four methods work with the LED (depending on the turning relay). Therefore the LED turning light must use 21 W (which would be stupid as it doesn't need it) or it sends an so called "ISO-pulse" to the relay telling the relay that the LED is working. Some of the Nolden headlights can be programmed to switch between these modes.
Simple example: WIth the Grenadier the Daytime Running Light switches to become the turning indicator (white LED to yellow LED). The Grenadier monitors the DRL but it must be aware, that this is also the turning indicator. So if the DRL ist turned off (to become the yellow turining indicator) Ineos must code that into its ECU that no failure is logged. Easy: If you get the signal that the turning indicator is turned on, switch off the DRL monitoring- Then wait x seconds. If another turning indicator signal arrives (still turning) reset the counter and wait again for x seconds and so on. If the turning indicator signal disappears and the DRL ist not coming back after x seconds: failure! If it comes back, everything is ok. The light can be dumb to realize this. Only the ECU of the car must be aware of what's happening and must just monitor the load.
It is a different thing for headlights as they use LED clusters. Law requires that the driver gets aware of any degradation of the light. If one part of the LED cluster fails you won't be able to see that. Therefore the light monitors its cluster itself. If one part of the cluster fails the whole light turns off. Of course, this monitoring is implemented in the light, not in the car, because that is something the light manufacturer has to do as it touches the internals of the light the car manufacturer not necessarily is aware of.
A headlight which fails and turns off fullfills this legal requirement as the driver is able to see that one headlight has failed (this way the LED just behaves just like a broken bulb, because it must. It would be able to still send out enough light but it is not allowed). The specifications between car and light manufacturer will list the necessary actions the car manufacturer has to implement in its ECU to monitor all the lights it must monitor and where it is just a comfort function. That is how this is done.
That makes it possible for the light manufacturer to present just two wires per light function to the car manufacturer, plus and ground, and that's it.
In modern trucks you can announce lights. You can program the ECU how many lights you use and which power they consume. So the ECU can adopt to variable loads, if you add or remove additional lights. But still no CAN bus is required, as this is simply done via load measurements.
However, car manufacturers tend to use the CAN bus for all that, because than they have a single system for all. But then the car manufacturer must be willing to pay the higher development costs for attached devices, like lights. And that makes things far more expensive. CAN bus could be necessary where you need an exact control of a function or its load in regards to save emissions or power (E-cars) and if it is not just a question of "on or off".
AWo
..none of the new fangled TV rubbish.
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