Hisun Sector E1 code 54C 3

Hello, I have the same issue. I tried testing all the batteries and all says 6.0 volts. That code 54C 3 comes on soon as I turn the key. The company I bought this thing from is out of business. I have had this issue for about 8 months. Know one works on electric golf carts and Hisun said it might be a main board. Lol. I will never by a Hisun or electric golf cart again!