LED trailer indicator lights pulsing

So does this pulsing/rapid flashing phenomena only happen if you have LED trailer indicators?
Or does it happen if you have std indicator bulbs but have LED brake/parking lights?

DG,
Indicator circuit only, as this is where the pulse is sent for bulb checks.

Cheers.

Hi Ducks guts,
Sniegy is spot on, all the other lights worked a treat, the pulsing only came through the indicators, this happened as son as I connected the light cable, and didn't stop util I disconnected the cable. I now have the magic lead from Linear Electronic Design and everything works a treat. Great forum this!!!

Strange.
I just tested my c/van that has full LED lights by hooking up to the D4.
No pulsing of the LED indicators. Everything operated as it should.
How lucky am I!:D