Hi folks.
I bought a 2003 Lexus RX300 and am having some trouble with it starting every once in a while.

I do not like carrying the big key fob so I like to use the Valet key.

It appears that when I lock the car with the key or use the lock button on the door, it immobilizes the system sometimes.
When it does, the fobs may or may not unlock the car. I have to use the physical key to unlock sometimes, but when I do the car will not even crank. I can usually get it to start working again by randomly locking and unlocking the doors.
Sometimes I can get it to work by trying to use the fob with the door open. It will beep. I hit the unlock button and now everything works again. This does not always work, but some random action I do seems to get it to work again. I have also had it refuse to crank after having it in accessory mode for 30 mins or more.
None of this seems to be consistent, but happens often enough to be a pain.

I drove it with the Valet key last night and when the wife tried to drive it today, her fob would not unlock the doors. I went out and used her physical key to unlock it, put her key in the ignition and it started right up. Inconsistent and weird.

When this happens, the lights on the dash come on but when I go to start, nothing. It just does not crank at all.

I have searched for hours over the past few days, but cannot find a similar thread. I am new to Lexus, so I may not know the proper terms to search on. Any Ideas on how to fix this?
TIA,
girdnerg

 

Why is the other key [master?] larger in size? There is a very slight difference from valet key.

There is a quirk in the electronic key system. If your RX gets a RF signal from another source [same frequency but with a non matching handshake code] it will disable the remote unlocking. This feature is there to prevent scanner-broadcaster from trying to unlock your vehicle. The only recourse is to unlock with the metal key (this also resets the receiver).

I recommend that all RX owners have 2 master keys and 1 valet key.

Please do not intermix the immobilizer with RF remote functions. There are procedures listed on the forum to relearn BUT do not mess with immobilizer function un-intentionally.

Salim
Other than some one trying the scanner-blaster, other RX owners who have the key-fob operate around your vehicle, can put you in secure mode as the frequencies match.

 

I do have 1 valet key and 2 master keys.
The head on the master key is a fob and is quite a bit larger than the valet, even though the valet is still too large for me.

I know it is not from a scanner-broadcaster as it has happened when I am fishing with no other person around for miles.

The valet key is the only key on my key ring with a chip in it. My other car and truck are too old for chip keys.
I have not seen any other Lexus cars in my neighborhood for them to interfere.

Any other ideas?

thanks,
girdnerg

 

I am new to Lexus, too. Recently acquired a 2000 RX300 AWD. She’s got a lot of miles (231k), but runs and drives great. 🤞

I wish I could be of more help. Mine came with only one key, apparently a master. It has lock, unlock and panic buttons on it. The unlock button only works on the driver’s door. I have to manually unlock the other doors and hatch with the key or with the driver’s side door panel switches once I’m inside the vehicle. I’d like to have another key made. I will research that subject and the quirks of my particular fob here.

Thanks to everyone here for keeping this forum going! I’m learning a lot. I appreciate all of you.

 

Before chasing potential FOB issues, start with the inside lock/un-lock buttons at the front. 99% of lock problems are due to worn actuator motor. Plenty of information and repair procedures are reported here in CL.

If the buttons work as intended and you still have a problem then move to key-fob transmitter and in cab receiver.

Salim