The other day I had to have my TPMS replaced in one of my tires. My 2010 wt 2.9L never had a key fob. When the mechanic attempted the relearn, he stated in went into limp mode. And they kept asking for the key fob. Has anyone ever heard of this when trying to relearn the TPMS? It doesn't make sense to me. Can anyone explain if this is possible and why it would be?