A Mazda 2008 passenger car with a mileage of about 38 thousand km, equipped with 2.3L engine and manual / self transmission. User response: when the vehicle is running, all kinds of indicator lights on the dashboard suddenly light up and the engine stalls. The car restarted, and the vehicle had no response at all. After receiving the car: confirm the fault symptoms and find that no matter whether the gear lever is placed in N or P position, the engine does not respond when starting. The ignition switch is opened, the charging indicator of the dashboard, the oil pressure warning lamp, the engine fault light, etc. can be lighted, and the information of the automatic transmission gear position is shown to be normal. It is OK to check the plug and fuse of battery, power supply cable, starter. Find the starter relay, turn on the ignition switch, switch the starter relay's contact switch, starter running, but the engine has no signs of car. The self diagnosis of the engine system by the diagnostic instrument and the interruption of communication seem to be a problem with the power system control module (PCM). Check whether the working power and grounding circuit of PCM are normal. Referring to the circuit diagram, we know that PCM has two power sources, one is the constant fire power supply, and the other is the power controlled by the ignition switch. Inspection revealed that the fuse controlled by the ignition switch fuse (15A). The resistance of the fuse to the earth is about 0.5 ohms with multimeter, indicating that there is a short-circuit phenomenon in the circuit or component at the back of the fuse. The fuse is used for power supply of PCM and ignition coil. PCM is less likely to damage, so check the ignition coil first. The engine adopts an independent ignition system, and each cylinder has an ignition coil. After measuring, it is found that the 2 cylinder ignition coil is short circuited. The replacement treatment is carried out, and the failure is completely eliminated. The installation position of the Mazda six ignition coil is shown in Figure 9-26. Due to the short circuit of the 2 cylinder ignition coil, the fuse that is supplied to the ignition coil is burned, and the fuse supplies PCM at the same time, so the engine can not start. The key to detect the ignition coil is to measure the resistance between terminals. By comparing the measured values, we can find fault components and remove faults.