why is the key fob locking me out since changing a small battery s type 2003!

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I had replaced battery inthe fob key.about 5weeks ago ever since the the car will lock me out won't start and lock the luggage door out it been 4 times ever right now haven't been abell tostart the car i have grocceries locked in my truck for the last 2days it keep stateing restricted performance. check engine light. the person i purchase the car from has a shop and each time i 'd it towed twice to the shop and then as soon as it drop off the car unlockes every thing with out him having to do nothing but turn the key, he then tells me not to use the fob key button to gain enterance to the car and if the button are pressed it locks me out again , in need of some real help PLEASE LOOSING MY MIND