Harness error leads to open circuit
In the manufacturing process, since the production of wire harnesses still relies on manual assembly, it is inevitable that wire harness errors will occur, and the quality inspection of wire harnesses can be checked with the help of electrical inspection stations. It is not repeated here. However, in the engineering development stage, wiring harnesses are often temporarily modified or hand-made, and errors are inevitable.
In the whole circuit, only two PIN pins of BMS are not directly connected together. Therefore, if other electrical appliances and wire harnesses are well connected, the continuity measured from the 2 PIN pins of the BMS wire harness should be on. During the inspection process, firstly, after confirming that the circuit is indeed blocked from the wiring harness corresponding to the 2 PIN pins of the ECU, the “dichotomy” method is used for inspection. From a PIN pin of the corresponding wiring harness of the BMS, measure to the PIN pin corresponding to the PDU (actually, a unit or module that is easy to operate) is measured, and it spans several modules. If it cannot be turned on, the scope of the fault is quickly reduced by half. Next, continue to narrow the scope of investigation from the side where the fault at one end of the BMS is located, and finally lock the location of the open circuit.
If the measured low-voltage wiring harnesses are all connected, the faults of the electrical appliances can be considered, such as the failure of the interlock switch of the PDU, the damage of the interlock terminals of the high-voltage wiring harness, and the short-circuit of the circuit to the ground or to the electricity.