I have an aftermarket key that was programmed using a tool since I don’t have a master key. It was cut to the same pattern of my valet key. Lately, the key will not work. When the key is put in the ignition, the security light flashes. However, it will work if the lock and unlock button is pressed SOMETIMES. When it does work, the car crank and starts and immediately dies. I have to press the gas peddle for it to not die out.

Keep in mind, my Lexus valet key works just fine. Starts the car fine. The aftermarket one has the issue only.

One thing to mention, the battery was replaced. I have no clue if that has anything to do with it. I’m new to the GS.

Any suggestions?

It is programmed though. It would work fine before. Start up just fine. Some days, it decides it doesn’t want to start with that key.