Front Marker Lights

Hi again. Since I'm coming up to my annual MOT on my 2010 Autosleeper Devon I thought I'd have another "stab" at getting my front marker lights to work. An ongoing defect having exhausted the usual faults, ie fuse 2 in the EM50, bulbs, holders, connections etc. Spade connections have all been replaced and there is a earth return from each bulb holder. So I eventually found the supply wires via the overhead panel lights. By putting an independent 12v supply both front marker lights work. Incidentally the rears have always worked. So great I thought, run a cable from the lights direct to the vehicle side lights supply. Yes initially it worked then I believe the CANBUS system decided to cut supply to the vehicle side lights and my newly installed cable to the front marker lights. Back to square one! The same thing happened when trying to take a supply from the rear marker lights. Again the CANBUS system cut the supply. One odd observation is that removing the Fuse 2 from the EM50 does not isolate the rear marker lights supply? Just about run out of options and hope the MOT tester records the fault as an observation. So is there anyway to "fool" the CANBUS system when connecting into a light circuit? Sorry for the lengthy epistle but trying to trace the original wiring to the front marker lights without a detailed wiring diagram is rather difficult. Of course perhaps AS have independently fused the front marker lights??  
Thanks for any inputs.

Update. Have solved the problem, I hope! Ran a supply from the back of the sidelights direct to the front marker lights. Not something I liked doing. Using Canbus sensitive bulbs seems to have stopped any signals to the system. Just an observation on the 2010 Sprinter lights. Does the ignition need to be on to activate the headlight flasher and mainbeam? Never noticed it before. Side and dip lights work without ignition.

Dipped headlights should revert to parking lights when ignition off.
By the sounds of it you have go through the whole system, with a wiring diagram.
If your main beam can stay on, i would be concerned as to what else is drawing current when you switch off. Good luck.

Thankyou Mollytardis. I think the lighting system is operating as it should. With ignition off not being able to select headlight "flash" or main beam. Just a little paranoid after breaking into the CANBUS wiring system. Hopefully someone with the older Sprinter, 2010 can confirm that it's operating correctly?