The function of the electronic control unit (ECU) is to receive the signal from the sensor, analyze it, and then transmit it to the actuator. Commonly known as "car computer". Generally speaking, ECU is damaged for the following reasons: 1. When welding and repairing the frame, the ECU wire was not disconnected. Because when the frame is welded and repaired, the change of current will produce extremely high induced electromotive force, which will cause harm to ECU through the circuit. 2. When the battery power is insufficient, directly charge it through the thyristor charger. Higher harmonics generated by thyristor circuit will damage ECU. 3. Or because the charger voltage is too high, the polarity is reversed when charging, or the ignition switch is turned on or even the generator is started. 4. When the maintenance personnel disassemble the ECU at will, touch the interface of the electronic control unit with their hands or weld the CMOS chip of the ECU with a soldering iron without grounding function, the CMOS chip may be broken down by static electricity. 5. When the engine is running, the positive and negative poles of the battery are suddenly disconnected. In this case, the circuit will produce high induced electromotive force, which may lead to the breakdown of electronic components inside the ECU. 6. Maintenance personnel are not familiar with the circuit system, or accidentally connect the wrong circuit, resulting in ECU damage. Generally, external short circuit will not damage ECU, and ECU is protected internally. Even if the pin is inserted incorrectly, it will not cause damage. However, depending on the specific ECU situation, the current ECU protection measures are perfect, except that the power supply port is fragile. Generally, high voltage is easy to damage ECU, but the voltage in the car is generally less than 15V, which is relatively safe. What is more dangerous is that the induced voltage generated by welding is sometimes very high, so it is best to remove the ECU when welding in the car. Also, the ECU itself is broken, mainly because of the quality of the equipment itself.