Permanent Fault Codes
Permanent Fault Codes (PFC's)
PFC's are very similar to a regular Diagnostic Trouble Code (DTC), except that they cannot be reset by disconnecting the vehicle's battery or cleared using a scan tool. PFC's are DTC's that are stored in the EEPROM memory of some Electronic Control Units (ECU's) starting in 2010. Only DTC's that illuminate the Malfunction Indicator Lamp (MIL) will be stored as Permanent Fault Codes.
Starting July 1, 2019, the presence of Permanent Fault Code's will be considered in determining the vehicle's smog emission test result in states which require emission testing.
Vehicles that have a PFC stored in the OBD system will fail the smog emission test regardless of whether the MIL is illuminated because a stored PFC indicates the OBD system has not yet successfully verified that a previously detected emissions related malfunction no longer exists.
All PFC's must be cleared in order to pass state emission testing. The scan tool can be used to check for PFC's in the "GUIDED DIAGNOSTICS" tab. The DTC number and Electronic Control Unit (ECU) storing the DTC will be displayed for each PFC. Not all vehicles built after 2010 store Permanent Fault Codes in the ECU's, therefore if it is not applicable for the vehicle, then no PFC will be displayed in the "GUIDED DIAGNOSTICS" tab. If there are no PFC's stored in any ECU then no further action is required and PFC's will not be the reason for state emission testing failure. However if there are PFC's stored, they must first be cleared to pass state emission testing.
There are only two ways that PFC's can be cleared:
- Three successful trips (no recurring faults) with the diagnostic monitor running and passing will naturally clear the MIL and PFC's.
- After the vehicle has been repaired and the DTC erased with a scan tool or a battery disconnect, complete one successful trip with the diagnostic monitor running and passing.
It is important to note that this does not need to be done during every normal repair action. Repairing an issue and erasing the DTCs with the scan tool will turn off the MIL after performing normal repairs and erasing the DTCs with the scan tool. It is only necessary to check for PFC's when a repair for a DTC is done to a vehicle, and that vehicle needs to pass smog emission testing.
There is one other scenario where a vehicle can pass state emission testing with a PFC present. If the vehicle completes 15 or more warm-up cycles (as defined below) and has been driven 200 miles or more since the OBD information was last cleared, the emission test will pass because the time to complete 15 warm-up cycles and drive 200 miles is reasonable for vehicles to complete the self-diagnostic tests. When the DTC fault is repaired the diagnostic monitors and PFC diagnostics should naturally run and clear long before these limits are reached.
- One warm-up cycle is defined as: The engine coolant temperature increases a minimum of 40°F (4.4°C) and reaches at least 160°F (71.1°C) during a drive cycle.