To check the transmitter strength, you can bring your key fob to any repair shop that has a TPMS tester which is capable of testing transmitter strength to see whether you need a new battery or whether there is a faulty transmitter, and also compare your transmitter to other similar transmitters that fit into your vehicle; some auto parts stores also do this. To replace the battery, a small flat screwdriver or a coin should be used to open the upper and lower parts of the key fob transmitter then slide the mechanical key and electronic half out of the lower half. Take out the battery, and make sure that you record the polarity marks so that you install the new battery accordingly and then slide the upper half back to the lower assembly and ensure the key fob works. To program transmitter keys, one needs an original equipment key fob and synchronized, which will necessitate a proper scanner and information and a locksmith license- there is also the availability of aftermarket key fob key fob using some vehicles and generally it comes with instructions to synchronize the key fob.