History Code

After a code has been set, the PCM continues to monitor for the test and failure conditions. For most codes, if the test conditions are true and the failure conditions are false, the code is changed to history. Some codes require the test conditions to be true and the failure conditions false several times or require an ignition cycle to change from current to history. If there are no current codes for a period of 50 ignition cycles, all history codes will be cleared.