Originally Posted by wpoll

This is why you need to add capacitors to non-facelift LED tails when fitted to a facelift model- the PWM signal won't work with the LEDS properly without some sort of averaging circuit (a capacitor). This averaging is done by the tungsten filament in normal incandescent tail lights.

This PWM is nothing to do with cold-monitoring - although that is there too. The PWM system driving the tails cannot be controlled by coding - you would need to replace the LCM.