Diagnosis System

DIAGNOSIS SYSTEM




a. As shown in the diagram, all ECU on this vehicle are connected each other via communication buses through which various signals are transmitted. These communication buses are diagnosed by the Body ECU (Main). When the Body ECU (Main) detects a communication error between ECU, or B+ short or GND short of a communication bus, a DTC is output and stored. The Body ECU (Main) 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.




b. If 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.