Description of On-Board Diagnostics

DIAGNOSIS SYSTEM




a. As shown in the following diagram, ECUs of this vehicle are connected each other by communication buses through which various signals are transmitted. These communication buses are diagnosed by the gateway ECU. When the gateway ECU detects a communication error between ECUs, or B+ short or GND short of a communication bus, a DTC is output and memorized. The gateway ECU cannot diagnose accurately unless it can function normally. Therefore, first confirm the normal condition by performing a "BASIC INSPECTION" described later and then, troubleshoot against each DTC. This multiplex communication (gateway) system consists of 3 BEANs (Body Electrical Area Networks): the door system communication bus; the instrument panel system communication bus and the light system communication bus and AVC-LAN (Audio Visual Communication-Local Area Network) communication bus related to the audio and navigation system. (Dealer option (cellular mobile phone, etc.) communication network can be added to the above.)
The gateway ECU forward data between BEANs and between a BEAN and AVC-LAN and transmits data between ECUs.




b. It DTC of ECU communication stop is output, connectors may be disconnected, or communication buses may be open at 2 points. It will not become abnormal with only 1 communication bus open.




c. If 2 communication buses are open at the position as shown in the illustration, DTC of ECU communication stop between those 2 buses is output.