Diagnostic Bus System: Notes

The Diagnostic Bus System is made up of two separate bus-systems which allow the DISplus to communicate with the vehicle control units via the diagnostic socket:

• The Diagnostic bus (ISO 9141-2 OBD II):
  • This allows communication with the DISplus and power train (emission) related control units
• The DS2 Protocol bus:
  • This connects to the control units that do not affect emissions and to the instrument cluster (IKE), which enables communication with all the control units on the K-bus system

The Diagnostic bus uses a single wire transmitting at 9,600 bits a second. The diagnostic line is used by DISplus to interrogate each control unit on the network and helps in the fault finding process. It uses a protocol very similar to that of the K-bus system and is accessed by DISplus via the 16 pin diagnostic connector located in the driver's footwell (under the dash, close to the A post).