Permanent DTC

In accordance with SAE J 1979, ECM stores DTCs that adversely affect vehicle emission (i.e. DTCs with MIL turning on) in non-volatile RAM (NVRAM) separately from that for pending and confirmed DTCs. This DTC is called a permanent DTC.

Unlike pending and confirmed DTCs, the permanent DTC will not be cleared even when executing the clear command of scan tool or when shutting off the power to ECM. The permanent DTC is cleared only when the ECM detects no malfunction in the trouble area of the permanent DTC. (For permanent DTC clearance, refer to DTC CLEARANCE .)

Up to four of the most recent permanent DTCs will be stored in memory. The DTCs are cleared once a full determination has been made that they are normal.