What is Permanent DTC ?
These are the new, emission-related DTCs that can’t be cleared from the ECM or TCM until the computer knows for sure that the problem was fixed. This usually involves performing a Universal Trip Drive Pattern exactly as described, but there are other ways, such as performing a dedicated monitor cycle. Permanent DTCs first appeared on certain 2009 vehicles, and are being legislated on 2010 vehicles. As with any new technology, the “glitches” may need to be worked out in the field, so reading the repair manual and TSBs are important steps before beginning diagnosis
Universal Trip Drive Pattern
So, how to clear a Permanent DTC? By performing a Universal Trip Drive Pattern that meets the strict criteria in the repair manual, to prove to the computer that the fault has indeed been repaired and no one is trying to cheat on an emissions test. After performing this Drive Pattern, if the code doesn’t clear it’s usually because the strict criteria were not followed exactly. It’s a pain, but that’s the way it goes.
Typically, this Universal Trip Drive Pattern starts off by clearing all the DTCs so that only the Permanent DTC remains (always refer to service information for applicable information and procedures).
Then turn the ignition ON, start the vehicle and let it idle for at least 30 seconds. Then, without cycling the key, drive the vehicle for at least five minutes at more than 40 km/h. Then (again without cycling the key) let the vehicle idle for at least 30 seconds before shutting it OFF. The whole drive cycle must take at least 10 minutes. After performing a Universal Trip Drive Pattern, the computer clears the code, since it’s “seen” that the problem is fixed and not reoccurring. Sounds simple enough, and most problems have apparently come from not performing the Universal Trip Drive Pattern correctly, but time will tell if these new DTCs will be problematic.Permanent_DTCs