Now just hold on there. I think it's the case that the TPS Diag 1 message should only normally be shown when you have the diagnostic leads connected - right? (Someone want to confirm that?).
Otherwise, Diag 1 seems to be some sort of red herring general error message that may or may not be factory but definitely indicates something amis.
I had a long breaking down saga coming back from the Donnington GP qualifying - I finally traced it back to a melted fusebox - but every time the fuse lost contact and the ignition cut out, the dash reported Diag 1. I've also heard of other people getting it with unspecified problems. So, sorry to worry you but you may have some sort of electrical problem.