WOW Zuberman! That's some educational stuff. This is starting to get a little out of my scope. I have the Code 21 and the car just died for no apparent reason. The next day is started right up. Someone sent me the recall information so I was going to go to my local Nissan delearship to have them change the PTU. I am thinking this is my problem since the car started fine the next day(due to being it cooled off) Does anyone disagree that this is probably the problem. Thanks for everyone's help and I hope this helps anyone in the future. Chris