2012 Plug-In Prius:
Recently, the red triangle light on the charging cable (not the dashboard) came on and it would not charge the car’s battery. The service manager at my Toyota dealer said the only problem he had heard about was a loose ground prong on the cable plug. Sure enough it was very slightly loose. I plugged it back in (I had done this before) and this time it worked. The plug is disassemblable so the next time I might take it apart. It was suggested that I might just replace the entire plug, but that would obviously void the warrantee, assuming it has one.