most auto parts stores have a key signal sensor tool. My Chevy dealer also had the tester tool. Before spending money on keys or batteries, I suggest checking that first. If it checks out that the key is functioning and sending out a signal and you are unable to program the key, then I would consider a new key. That said be sure you are VERY familiar with how to program the keys. The procedure is easy to mess up.

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2001 BMW X5 3.0 5spd Sport
-aFe Intake
-E46 Sport seat retrofit with Heat
2007 Mini Cooper S 6spd