How was the battery tested? Was it load tested? Also, keep in mind, batterys can short out internally. The clicking indicates the starter isn't getting enough power.
As far as the check engine light, if it has been on, there is a code stored in the computer. If you take the car to a nationally recognized parts store, they will most likely scan the computer for free (no money out of pocket) and then you'll know why the light is coming on.
Let me know.
Joe
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Monday, June 22nd, 2009 AT 10:40 PM