DTC 12

The "Check Engine" malfunction indicator lamp should flash diagnostic trouble code 12 three times consecutively in diagnostic mode. This would be the following flash, sequence: "flash, pause, flash - flash, long pause, flash, pause, flash - flash, long pause, flash, pause, flash - flash". diagnostic trouble code 12 indicates that the engine control module's diagnostic system is operating. If diagnostic trouble code 12 is not indicated, a problem is present within the diagnostic system itself, and should be addressed by consulting the appropriate diagnostic chart.
Following the output of diagnostic trouble code 12, the "Check Engine" malfunction indicator lamp will indicate a diagnostic trouble code three times if a diagnostic trouble code is present, or it will simply continue to output diagnostic trouble code 12. If more than one diagnostic trouble code has been stored in the engine control module's memory, the diagnostic trouble code(s) will be output from the lowest to the highest, with each diagnostic trouble code being displayed three times.