Make sure everything is grounded good. Had my trannie rebuilt last summer in
my Elantra. It worked fine for a few days then went into the safe mode. Took
it back to the guy that rebuilt it. He checked the codes, but the readouts
were basically jibberish. Ended up that the ground cable from the battery
was loose down underneath the car. I'm sure they had that loose when they
removed my trannie, don't know whether they didn't get it tight in the first
place or if it vibrated loose, but they fixed it and the car is working
properly. It would sure be worth a look!