Installed New battery’s in Aug. Last Tuesday Battery Light came on. I checked the charging system it wasn’t charging I replaced the alternator. It is charging at 14.3 volts now. When I started the truck the light turned off then after about 15 sec. it came back on. Check codes it had P0620 and P1000 cleared codes and started it again same thing I did this about 3 times and same results everytime so I desided to drive it for a while. Some improvement now it stays off for about 4 min. The only code I get now is P1000.