Diagnosis Bus (D-Bus): Introduction

The D-bus is a serial communications bus which can transmit data between the BMW DIS or MoDiC and the connected control units. The control unit to be subject to diagnosis is selected by sending a diagnosis telegram to the control unit address. By request from the tester, the control unit can transmit information and the contents of the fault memory or activate a control unit output. The D-bus is only active when the DIS or MoDiC is connected to the diagnostic socket and communicating.

The D-bus is actually the oldest bus system used in BMW vehicles, it was introduced in 1987 as TXD which provided communication between DME and the Sun 2013 Service Tester. The D-bus is still referred to as TXD in the ETM.

Data over the D-bus currently operates at a rate of up to 9.6 Kbps (bits per second).