Using LED tail lights in combined lights for Toyota Previa might not work

Using LED tail lights in combined lights for Toyota Previa might not work.

I have read elsewhere that older cars can have problems with having combined LED taillights. You know the taillights and brake lights are combined in the lamp. Therefore, I tested the poles to see if they were minus when the function is not active.

Ground - earth on positive poles when not active. Which might short circuit a led lamp since the LED-lamps often are connected.. The LED lamps have to be separeted or you will probably need a resistor to take the load, since in my view a "crappy" design.