I am getting a check engine light at various times driving to and from work, (afternoon, midnight). There does not seem to be any rhyme to when the light comes on. However, each time I try to read the code (OBD1) there's nothing in the computer. The light doesn't even flash indicating no codes. Could this be an indication of a bad ECU? When the light is on the engine does not seem to go into "limp" mode. Any suggestions? P28 ECU