History DTCs

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