this^^^Sounds like its in limp mode. First, I'd check the trans fluid level.. its not likely, but its easy to check and fix. THen, i"d get a good scanner and check for transmission codes. It wouldnt necessarily throw a CEL, but could still have a code. A regular obd2 scanner won't read this. Have him unplug the battery for a couple min and re-connect it. That may 'reset' anything that could be messing it up. Other than that, he's going to have to bring it in for a diagnostic at a shop w/ a good obd scanner that can see whats going on w/ it.