I'm curious about the battery/key situation ref my 2003 Lexus LS430.

I've owned the car for about 2 years. My brother was the previous and original owner. I was reading up on the keys as it was past time to replace the batteries. I can't get the main keys apart to replace the batteries so the dealer's parts department did it for me.

In the process of reading, I realized I didn't have a subkey and my brother has no recollection of having a subkey. I do have the flat key.

It looks from the manual photos that perhaps the subkey does not require a battery - hard to tell. No room in the flat key for a battery.

What is going on in the main keys that requires a battery that apparently the other two types of keys don't? Thanks.

(I miss the happy days of my old previous car when a key was just a key.)

 

The main (master) key requires a battery for the lock/unlock/trunk buttons. The subkey (valet key) lacks these buttons, so does not take a battery. Both keys have immobilizer chips, so the car will not start unless programmed electronically to the car.

 

So the subkey will lock and unlock the car doors?

When the main key had a dead battery it did not lock and unlock the car doors, which theoretically one might think it would do since that does not require a battery...

 

Just like a when a key was just a key, both types of keys should manually unlock and lock the doors (using the metal part of the key) and start the car. However, the subkey will not open the trunk.

Think of the main key as a key with a remote built into it. The remote needs a coin type battery to send the lock or unlock signal to the car. So if the key battery is dead, you will have to manually unlock the car using the key blade. Just like when the batteries are dead on your TV remote, it won't turn the TV on.

 

Thanks everyone.