Car is a 2000 Boxster S

After replacing the battery in my keyfob, I can press either button and see the redlight flash.

However when I try to pair the key via locking the car manually and then unlocking the car manually and trying to press the button to pair the key, the light on the key will only illuminate sometimes.

I've also tried the other method of turning the key to position 2, turning the car off and removing the key, and pressing the button. Here again the light on the key will only illuminate sometimes.

What is my next plan of attack to get this working?

 

I’m not aware of any way to reprogram a key outside of the dealer. Did this key ever work, prior to the new battery?

 

It used to work. Stopped working one day.

I even disconnected the car battery for 20 minutes as I hear resetting the car computer can sometimes solve the problem.

The bizarre thing is that the red light on the key always illuminates when you press either button except sometimes when I try the "pairing procedure" with the ignition or door lock. Often times right after the pairing procedure the red light will NOT illuminate. So it seems like some type of communication is happening.

 

I agree: Some type of communication is happening. I would suggest communication between the batteries and the red light... revealing that the batteries are good, and the red light works. Check some other forums regarding this problem... use the forum "search" function... and you;ll find a ****lo... er... a lot of good information. Your question already has been asked and answered, a million times. Good luck!

 

All that the blinking red light is telling you is that the battery and switch are good and that the electronics in the key are (to some level) powering up. I just walked the dog, well out of range of the remote, and the red light flashed just fine. The car did not lock, nor did the trunk latch release.

I'm kinda assuming that this is the only key you have? It may be worth pulling the immobilizer module (it's under the driver's seat in LHD cars) and inspecting it for water related damage.

 

It appears that the key & immobiliser may have gone out of sync. Remove the keyfob battery & insert it for a minute the wrong way round. Then remove & put it in the correct way & try to use it again after following the manual lock/unlock pattern.
Please update this thread thereafter.

 

Thanks.

I tried it. No luck.

The key fob now consistently illuminates red when pressed in any scenario but the car is unresponsive.