On a 2015 500X each light unit has TWO 12V 21W bulbs wire in parallel. So for side lights the bulbs are driven by modulation so as to deliver lower average voltage to the bulbs and thus produce less light intensity. When the brake pedal is pressed the full 12V is delivered.
If we talk normal bulbs then the combined resistance of the bulbs is HALF that of a single 12V 21W bulb, and the system will detect when when just one bulb has failed. I've not personally measured to see if the body computer sends low sensing voltage / current through the complete circuit even when the side lights are turned off. This could be tested with the old light unit and with the ignition on but lights off remove one or both blubs to see if this detected.
I see the Osram kits is just basically two (so called) 21W metal power resistors. I think their 21W is just the sales marketing rating to be aligned with 21W bulb. These Osram resistors look more like 15W aluminium clad wire wound items.
The power rating is regardless of voltage so their resistance value could be anything. Also generally these metal cased power resistors are designed to be mounted on some form a heat sinking surface to reliably handle a full 15/21 Watts of dissipation.
You could try doubling up the Osram resistors (in parallel) to see if that solves your problem. If it does then ideally you need to measure the resistance of one of the resistors. You can then half that and buy a replacement instead of having two/four dangling items attached to the wiring loom.
See this as an example:
https://uk.rs-online.com/web/p/chassis-mount-resistors/0159792?gb=s
These types of resistors are quite cheap (sub £5) so the Osram kits are quite expensive at £30 to £100!
Also if I look at the official OSRAM website data sheet (
https://www.osram.co.uk/appsj/pdc/p...vid=MP_EUROPE_UK_eCat&lid=EN&mpid=ZMP_4064927) they don't specify the resistance value used either so you will have to measure yourself if doubling up fixes the problem.
