sold pred & new owner having issues

[bcfreighttrain]

sold u7131 with 9r03 on it to a friend with an 06 auto. he has had it for a while and has loaded and unloaded it a few times with no issues. He called me today and said that his cel came on while driving and he pulled over and checked dtc's and nothing came up on screen. he then tried to restore original backup and it wouldn't let him. he then continued to clear the dtc( 7-10 times) then tried original backup again and it worked.. what is this all about? any ideas?? he says that there is a rattle now when he revs the motor and it comes back to idle then it goes away.. i had this programmer for over 2 years with no issues. i thought maybe he is having injector issues being it is an 06, but hard to diagnose as he is 10 hours away from me. i told him to keep an eye on his oil level in case he has a cracked or stuck injector.. any help would be appreciated

[mikel]

Injector issue is likely, since as you said, it is an 06.