Ok, so I found some corrosion in the ECU connectors. I cleaned off the connectors and terminals at the ECU really well, erased the codes, and drove it for hours. Works fine now. Maybe the CAN codes were caused by high resistance. The ECU is in the back of the engine bay, maybe water was able to get in there easier due to old weather stripping. BTW, CAN C is 500kbits/sec, my mistake. Check ECU connections!