Canbus uses various models to control various parts of car’s electrical systems to keep wire numbers, length, compilation and costs down as ever more features and interlinking becomes necessary. Data connection between the modules carries command information on one wire rather than having one circuit for each function.
Step light and tgate open light take control from rear cab idpm
Cabin light is controlled by roof c/u
You may want to look in that direction if you dont solve the problem
Have a gud un!