Originally Posted by Crusher
not heard this before......... so which cars wont it work with??
The D3 doesn't like LED trailer lights along with most Canbus equipped cars developed before the manufacturers realised LEDs were useful for trailers and caravans.
The Canbus system sends a constant signal pulse down the indicator wires to measure the resistance and decide if a trailer board is plugged in.
LEDs have very little resistance compared to the normal filament bulbs so two things happen.
The dashboard warning light doesn't illuminate and the indicators pulse constantly as the LEDs can react to the small signal voltage which isn't enough to activate filament bulbs.
On a D3 and possibly others the changes made to the air suspension settings when a trailer board is plugged in are also not activated.
As has been mentioned the Canbus system can be fooled into thinking a normal filament bulb trailer board is plugged in by putting a resistor in the indicator circuit of the trailer board to mimic the resistance of a filament bulb.