I found the answer at http://www.obd-codes.com/p0601. It says that the Powertrain Control Module (PCM) needs to be replaced.
P0601 Internal Control Module Memory Check Sum ErrorThe engine computer has failed.P0601 Internal Control Module Memory Check Sum ErrorThe engine computer has failed.
Trouble code P0601 means: Internal Control Module Memory Check Sum Error
Trouble code P0601 means: Internal Control Module Memory Check Sum Error
Trouble code P0601 means:Internal control module memory check sum error
Trouble code P0601 means:Internal control module memory check sum error
Trouble code P0601 means:Internal control module memory check sum error
Trouble code P0601 means:Internal control module memory check sum error
Trouble code P0601 means:Internal control module memory check sum error
Trouble code P0601 means:Internal control module memory check sum error Trouble code P0602 means:Control module programming error
Pcm internal failure. The code P0601 ~ Internal Control Module Memory Check Sum Error. Chances are if you are getting this code then the ODB2 computer isn't storing codes like it should. It may even cause the vehicle to run bad or not run at all.
P0601, pcm internal failure. replace pcm
P0601 is Internal Controller Failure- Common repair is Install new PCM and program it.