Will Adding An Inline Relay Affect The Canbus?

I've tapped off the circuits on my BMW's, and they have not affected the canbus.

 

I don't see what the canbus has to do with powering an indicator, but I suppose it's feasible that the switching circuit for the indicator monitors the current to detect faults and that additional lighting load might make it think there's a fault. Wouldn't have thought so though. (Edit: you would obviously not want to overload the switching capability of the ECU which is driving the indicators, not sure what that would be, but you've got to assume it'll cope with an extra LED auxiliary light of similar power to existing indicators).

With regard to your proposed solution with the relay...

That diagram looks like you're putting the relay's coil in series with the indicator bulb, that's not going to work, you want it in parallel. I.e. one end of the relay coil connected to the side of the existing indicator that gets the intermittent 12V volts to make it blink, the other side of the coil connected to ground (possibly using the ground wire to the indicator if that's convenient).

Also, if it were me, I'd also connect a diode across the relay coil to protect to ECU against back EMF. It may have inbuilt protection, but it also may not as it's not expecting to switch an inductive load. That diode must be the correct way around, otherwise it's just act as a short circuit.

Note, I've not done anything like this on a bike, I just know how electricity works

 

Just don't cut into the CANBUS at all. The cost of screwing up an electronic component is just not worth it. The chassis control module developed a fault on my 2018 and it took the dealer over two months to diagnose and fix the fault. Luckily it was in warranty, unluckily these complex systems are extremely difficult to fault find, hence the two month fix. I hadn't touched my system and it was a random fault. If you trash a component and have to pay for it it will cost your a small fortune.

As brown mouse says, your relay wiring will not work.

Google this:
TriCAN-PCM - CAN-Bus Power Control Modulec It is not ready yet but might not be far off.

 

If you continue with your project I've found AES to be a useful supplier (and you can get diode protected relays here)
or here

 

I fitted some extra LED spot lamps to my Street Scrambler and just connected them straight across the feed to the head lamp. I also replaced the OEM halogen headlamp bulb with a LED H4 so the resulting load on the lighting circuit was actually reduced, even with the extra lamps fitted, hence no relay required. I'm not 100% on wether the SS has a CANbus system but I suspect it has as the indicator flash rate can be "reprogrammed" if LED indicators are fitted.

 

Yes, that's it. Diode connects across the relay coil in the direction that it wouldn't normally conduct electricity, i.e. pointing away from earth. Here's my attempt at drawing it...
Note, diodes are pretty much universally marked at one end with a band to mark the end that is at the top in the picture above.

 

This triggered my curiosity as I find the led indicators to be pretty good, why do you want auxiliary indicators ?

To aid visibility I have auxiliary light that are constantly on , I'll like to find a switched power supply for the relay, but my dealer warned me that cutting any wires will affect the warranty ... I'll wait 1 more year before splitting wires

 

Halfords do a relay with the Diode built in, it is just a couple of quid extra. The Diode is there to help protect your bikes electronics by prevent spikes being introduced when the relay is dropped out.