NHTSA Complaint #11663590 — 2019 TESLA MODEL X

While driving normally at around 30mph and without warning, the vehicle displayed multiple warning messages related to the HV Battery and lost all motive power in the middle of the road with insufficient time to pull over, creating a safety hazard. Upon inspection by a mechanic independent of Tesla, the HV Battery was found to have multiple voltage sense leads disconnected from the flexible PCB pads that lead to the BMB for each module. One of the 96 bricks had all four sense leads disconnected, resulting in the loss of motive power due to the inability for the BMS to accurately measure the voltage of that brick. In fact, the vehicle displayed module over voltage and under voltage alerts due to this open/high resistance sense harness connection. Out of all 96 bricks, 13 bricks had at least one loose sense lead, and one brick (besides the affected brick) had 3 out of 4 sense leads loose/disconnected from the PCB pad. Any loose leads were only at the PCB pad end, not at the current collector end. These sense leads are ultrasonically welded through the same attachment process as the cells, but the connections to the flex PCB pad are clearly not as robust as the other connections or are exposed to higher vibration over time due to relative motion of the flex. The flex PCB design was introduced in 2015, just before the Gen 2 HV Battery, and in production until the 2021 refresh. The HV Battery did not ever have any visible liquid ingress or physical damage. It is my understanding through various forums such as Tesla Motors Club that this is an increasingly common issue, and that Tesla is experiencing a high rate of this open voltage sense harness issue at their service centers for vehicles that have not been in any prior accidents or incidents (forums generally only have salvage vehicles that are out of warranty). Errors typically are: BMS_f107_SW_Cell_Voltage_Sensor BMS_f177_OpenVshDetected BMS_w129_SW_BMB_VSH_Connector Or their variants (a129, w177, etc.)