Will a Permanent Code Fail Emissions?

Conclusion. Permanent DTCs can cause a vehicle to fail a smog check even if the check engine light (MIL) is not illuminated.

How long does it take for permanent DTC codes to erase?

A Permanent DTC will be erased one of two ways:

After three consecutive confirmed fault-free monitoring cycles. The MIL is extinguished and the Permanent DTC is cleared at the start of the fourth fault-free monitoring cycle. After one confirmed fault-free monitoring cycle following a scan tool “clear DTC” request.

What does a permanent engine code mean?

Permanent codes are a special type introduced more recently which can not be cleared using a scan tool. If you have a permanent code the vehicle will clear it itself once the cause has been addressed and sufficient data has been gathered by driving under different conditions (idling, stop and go, highway)