问：立体声的接线线束来自灰色连接器中卡车的和弦的线束，有一个销钉缺少。

Sometimes radio wiring harness’ have pins that are missing on purpose due to the fact that there are more pin holes in the connector than there are wires. If this is not the case, it is possible that a wire has slipped out of the connector. However, if this were the case, the wire would likely be visible somewhere near by. It is also another possiblilty that the person who wired up the radio previously may have installed something incorrectly. Another thing you could try is locating a wiring diagram to find all the necessary wires to hook up your radio.