Engine ECU, ABS, etc. have a great influence on the performance and safety of the vehicle, and are easily interfered by other electrical equipment (such as audio, oil level sensor, etc.), the grounding of these components must be set separately. In the airbag system, the ground point must not only be set alone, but also a composite ground is required. The purpose is that when one of the grounds fails, the system can be grounded through another ground point to ensure the safe operation of the system. In order to avoid interference with other systems, the radio frequency signal needs to be grounded separately. The grounding of the weak signal sensor is best independent, and the grounding point should be near the sensor to ensure the true transmission of the signal. Other electrical components can be combined with each other to share the grounding point according to the specific arrangement. The principle is to ground the iron nearby to avoid excessively long ground wires, causing unnecessary voltage drop. Due to the large cross-sectional area of the negative wire of the battery and the ground wire of the engine, the length and direction of the wire must be controlled to reduce the voltage drop; in order to increase safety, the engine and the body are generally connected to the negative pole of the battery separately. It is necessary to distinguish the electronic ground from the power ground, and separate the analog signal ground from the digital signal ground to avoid mutual interference between signals. In the whole vehicle circuit system, many things need to be considered in order to design a reliable ground loop. The most important ones are as follows: shorten the ground loop length as much as possible, reduce the loop voltage drop, cost and weight; minimize unnecessary mutual interference between subsystems.