If there is an issue with the antenna amp under the rear glass, what exactly would the problem be and how would you fix it? For me it's gotta be that because my infrared signal works most of the time to unlock the doors and I can always start the ignition just fine.If they key starts the car just fine, but wont work for Remote Control Locking, then it's either (1) a weak or bad battery in the key or (2) a bad key or (3) a problem with the antenna amp under the rear glass. If they key also is not recognized by the ignition switch, then first try another key. If that works, then you have a dead key which will need to be replaced. If the other key doesn't work either, then it coudl be a problem with the vehicle battery, or the vehicle's security system (DAS/EZS).