I have a fix... doesn't make sense but it works.

My two key fobs had new Duracell CR2016 batteries placed in the keys and both appeared as dead. So I set an appointment with Toyota and purchased a new key online just in case my main key was worn out (12 years old and used daily). If they were going to have to reprogram my second key I wanted to have two working keys.

The new key came with a battery and I noticed when I pressed a button a red light would come on. It didn't on either of my original keys. So I took the new key battery out and put it in my main key, now my original key works again. Put it in my second key and it works, so it is programmed which I didn't think it was.

Pull out the multi-meter, both replacement batteries read 3.0 volts. Try the replacement batteries in the new key and no red light, try back in two original keys and no light.

So all three batteries I have are reading 3.0 volts, only one will work in all three keys and the two replacement batteries will not work in any key.

So I put the "good" battery in my main key and now have one working key and a different brand of batteries on order. Doesn't make sense, all three batteries are new CR2016's reading 3.0 volts, but only one will work in the keys.

Cancelled my appointment with Toyota.