故障现象一辆丰田卡罗拉车(搭载2ZR发动机),接通点火开关,MIL指示灯不亮,且散热风扇常转;起动发动机时,起动机可以正常运转,但发动机无法起动着机。故障诊断连接故障检测仪,读取故障代码,发现故障检测仪与发动机控制模块(ECM)无法通信,怀疑该故障是由ECM电源电路故障或VC输出电路故障引起的。ECM电源电路如图1所示,当点火开关置于ON位时,电流从点火开关端子6经熔丝IG2 No.2流向IG2继 Fault phenomenon A Corolla car (equipped with 2ZR engine), turn on the ignition switch, MIL indicator does not light, and the cooling fan often turn; start the engine, the starter can run normally, but the engine can not start the machine. Fault Diagnostics Connect the fault detector and read the fault code to find that the fault detector can not communicate with the engine control module (ECM) and suspect that the fault was caused by an ECM power circuit fault or a VC output circuit fault. ECM power supply circuit shown in Figure 1, when the ignition switch is placed in the ON bit, the current flows from the ignition switch terminal 6 flows through the fuse IG2 No.2 to IG2