I had the same problem. No matter what they did to fix it, (oxygen sensors, etc.) it would seem to be fixed, and then start all over again.
Then I noticed it is temperature sensitive. If the car is parked on blacktop or it is a very hot day, this happens - if it is 10 degrees cooler, it does not.
Since the error codes are heat sensitive, I am having the computer chip checked. I think the computer chip that monitors all the other systems in the car is itself bad. So it is reporting problems that do not exist whenever it gets hot