Hi everyone,

I'm troubleshooting issues of a recently purchased '04 LS430 that came without a smart key(3 button transponder variant), here is what I'm dealing with.

The problem:
1) Remote options on the key do not work. Trunk/panic/lock/unlock.
2) When the security system is armed, manually unlocking the car from the driver's side sets off the alarm SOMETIMES, but not all of the time. The car still unlocks.

The attempted solutions:
3) Changing the key fob battery.
4) Pairing a new remote key.
5) Disconnecting the negative from the battery and waiting 20 minutes.

Background Information:
Car battery is 3 years old and came from the dealership. Previous owner says the remote functions suddenly stopped working one month ago. Saw no evidence of water damage in trunk area (and the trunk seals look fine) and the region where I live one month ago did not have any heavy rain. No other electrical systems on the car give me any issue. The actuators all successfully cycle the locks (though I had to replace the passenger side as the motor died, but it now works again). The only recent service it had at the Lexus dealership prior to my ownership was replacing the passenger side mirror & front windshield.

Things left to try:
6) Inspect fuses, though I'm not entirely sure which ones.
7) Inspecting components responsible for 'receiving' the key transmission. I had thought that the part receiver, door control (89741-50460) may be the culprit, but a quick inspection of the trunk revealed I did not have this part. It seems very unlikely someone stole that, and only that, leading me to believe that this part may just be for the smart key variants of the car. If not, I can snag a junkyard one for about 40 dollars.
8) Taking it to a locksmith/mechanic/dealership.

What information the people of this forum could share in aiding me to pinpoint this issue would be extremely helpful.

Thank you.

 

Small update. I have a brand new OEM key, cut and programmed, but the remote functions still don't work.

My locksmith is certain the issue is on the receiving end. Does anyone have any insight into the receiving logic for the LS430 with the transponder (non-smart key)?