The mileage is only 5500km, the Volkswagen New Bora car equipped with 1.6L engine. Customer response: after the ignition switch is broken, the key is not pulled out and the engine will not turn off. Fault diagnosis: after the car, the car check. As shown in Figure 1, when the ignition switch rotates clockwise to the OFF position, it can start normally, but when the clockwise direction rotates to the OFF bit, the car can not be extinguished and can only be extinguished after the key is completely pulled out. Fault code is read by fault detector VAS6150B, and no fault code is stored. Referring to the circuit diagram, it is found that the power 30 is connected to the P terminal after the key is pulled out; the key is inserted directly, not rotated, the ignition switch is in the OFF position, the power supply 30 is connected with the P and s terminals; when the ignition switch is connected, the ON position is rotated, and the power 30 is connected to X, 15, S terminals. Through internal circuit analysis, the fault point may be in the ignition switch at OFF position, the power 30 terminal is still connected with terminal 15, and can not be completely disconnected. According to the above analysis, after the key was pulled out, the steering wheel hood shell was taken off, and the ignition switch core was removed from the steering column, and the short connection between the terminals was checked with the multimeter (Figure 2), and there was no short connection. Troubleshooting: at this point, it was considered that the fault was caused by the internal fault of the ignition switch, so the ignition switch was replaced. It is further speculated that there is a problem of installation between the lock core and the lock base of the ignition switch. Consult the maintenance manual, find the ignition switch installation steps, but there is no special requirement. After starting the engine, the ignition switch is rotated counter clockwise to the OFF position, and the ignition switch lock core is loaded. It is found that the ignition switch can be fixed to the core. The failure is excluded: the ignition switch is reinstalled, the distance between the lock seat and the ignition switch core is adjusted, and the fault is excluded.