code 0300....other than ECM have tried everything.....

Question type: Maintenance & Repair

1996 neon- installed a 1999 2.0L SOHC used engine to replace same engine. spark plug and wires-
cam sensor-thermostat-timing belt -replaced --injectors cleaned-all engine limits OK....P-0300 code
displayed-not able to reset light ..comes on in about 5 miles--I have not changed the ECM because
before engine was changed there was no trouble with the check engine light..no other codes
displayed....any one out there with any ideas?...also 7 sensors installed in car....check engine light will
not stay out even after reset....The does anyone out there know the chance of the ECM going bad as
everything else has been checked or replaced..also the engine runs like a top...? I believe that the
1999 engine is identical to the 1996 engine and the ECM should recongnize it as the same......