Probable Causes:

DTC 12 is caused by loss of "G" or "NE" signal from distributor to ECM for at least 2 seconds after starter signal is received at ECM. Check distributor and ignition system components. See SYSTEM/COMPONENT TESTS article. Ensure starter signal exists at ECM. See DTC 43 .

DTC 13 is caused by loss of "NE" signal from distributor to ECM when engine RPM exceeds 1500 RPM. Check distributor and ignition system components. See SYSTEM/COMPONENT TESTS article.