I have a new starter in my car and my ignition and switch are new. My battery is full and the accessory light is on. But I can't start my car. When I turn the key it won't turn over. Do I need to replace the starter relay?
The electronic immobilizer module completes the circuit to the starter once it has determined all of the parameters are correct. There is no stand alone relay, as it is built into the immobilizer module. If you are not getting power to the starter and have already replaced the ignition switch, my guess is that the problem is in the anti-theft system.
It could be the immobilizer itself or one of the inputs. You may also want to check the #31 and #28 fuse just to be safe. German electronics can be quite complex, so I suggest you have a professional diagnose and repair the starting issue for you.