The Comfort Access Subbus is a single-wire bus and it connects the following components of the access and driver authorisation system:
The status of the outside door handles is transfererd across the Comfort Access Subbus to the CAS and Comfort Access control unit. In the diagnosis system, it is possible to read the status of the outside door handles in the control unit functions of the two control units. If a readout is only possible at one control unit, the bus connection of the defective control unit must be checked. If it is not possible to read out the status of an outside door handle, the bus line in the corresponding door or in this area must be checked. The CAS is the simultaneously the gateway between the data buses K-CAN SYSTEM and K-CAN PERIPHERIE. For diagnosis of the Comfort Access control unit, is must be borne in mind that the CAS has to shift the diagnosis commands to the Comfort Access control unit on the K-CAN Peripherie bus. Without function of the CAS or K-CAN System and K-CAN Peripherie buses, no diagnosis on the Comfort Access control unit is possible. A bus interruption between CAS and the Comfort Access subbus can also lead to malfunctions in the remaining bus system. The terminating resistor of 1 kOhm of the bus is located in the CAS and is necessary for the reliable function.