Coolant temp sensor location

Permanent codes will stick around for a set number of drive cycles after the PCM detects that the fault was repaired. They cannot be erased with a scan tool. If you don't have a pending or current code for the same thing then it just needs the drive cycles to remove it from the system. The factory ISTA system can delete them earlier but I don't know of any other unit that does. You will run across them in many of the newer vehicles as well. Although they claim it is to prevent people from simply erasing codes I think it is more of a tattletale system, showing that you didn't take the vehicle to a dealer or "authorized" shop.
OH, there is only the single sensor on that engine.

It's a common problem in a lot of the Euro vehicles. They won't let the aftermarket tools erase the permanent codes.