what does "PCM failed self check?" and My PT cruiser computer gives me the codes PO601 P1684.

I was reading some of the questions you have answered. In April of 09 you told someone with the code 1684 that it ment PCM failed to self check and that you would get back to them later about the failed to self check answer. I have not been able to view what you said when you got back to the writer. My PT Cruiser just started missing and running so bad, I can not drive it. My PT cruiser gave me the codes P1684 and P0601. Could you please help me try to fix this car. Thanking you before hand for any info you can give me My 16 grandchildren do not want me to give up, this was the car they and their grandme always ran around with sincerely, the Gilliam family from Brooklyn,New York