1993 Park Avenue error code

I have a 1993 Park Avenue with 110,000 miles on her. I am having stall problems and so I checked the computer to see if there were any codes stored. At first, I saw no codes and considered moving on to testing the fuel pressure, etc. When reading the book on the error codes I found it said the car would flash '12' 3 times (the handshake code, then flash any error codes, then flash '12' 3 times again. I noticed it that '12' flashed alot more than 3 times (or even 6 if there are no errors), but it flashed on and on and on. Is this normal? Could this be a bad ECM? I have tuned the car recently, so I know it is not that. Also I replaced the exhast system. Please help!