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 becomes a history DTC. Some of the DTCs require the test conditions to be true and failure conditions to be false several times. Some of the DTCs require an ignition cycle in order to change from current to history. If no current DTCs are present for a period of 50 ignition cycles, all of the history DTCs clear.