Louie7

Hi...I'm sure everyone is tired of discussions about keys and transponders etc...I've looked and searched.

My 1991 and 1994 LS400's both have master keys with one button transponders (HYQWDT-B aka: Toyota part 89742-24070)

Problem is, even with new battery ...pushing the button does not lock or unlock the car. Push the buttom...nothing.

The directions I've read on this site for programming are for later models (like 1998) and clearly address the three button keys.

Anybody know the procedure for the programming with the ONE button keys?

Thanks very much.

CELSI0R

You cannot program gen 1 keys. The ROM chip is paired to the key from the factory. HYQWDT-B frequency is for 1993-1994 LS. 1990-1992 use a different frequency.

See here:
https://us.lexusownersclub.com/forum...comment=502381

If your key worked before with your car before the battery died, then there is a problem with the battery or the key itself.

Louie7

ok...got it...thanks.

CELSI0R

Sure. I really wish there was a more modular system equipped.

Did these keys ever work with your cars prior? Your 91 key should say HYQ1512A for the frequency.

Double check your batteries with part number in this post:
https://www.clublexus.com/forums/es-...ml#post8367709

Also here for the same battery part number:

Louie7

Thanks again. Here's what... the '91 and the '94 both came with non-working Master Keys. Both had batteries that, when removed, tested 3V, so I put them back in and tried again. Nothing.

Yesterday, I opened the key for the '94, which is my daily driver and took a close look. I discovered that the tiny metal tab was mashed down under the battery. What I didn't realize was that the battery needs to slip under the tab so the tab a can make contact with the top (+) side of the battery. Evidently the previous owner didn't know, or care and just jammed the battery in, mashing the (+) tab down under the (-) side of the battery which faces down.

Once I got the battery correctly installed, I went to the car and pushed the button. I was pleased when I heard the click and the door unlocked. Then I was disappointed when it stopped working again. I removed the battery and tested it again and it read less than 3 volts. So I drove to the hardware store and bought a brand new Duracell CR-1216 which tested over 3 volts at the store. I installed the new battery and now it works every time...so I'm happy.

My plan is to repeat this with the '91 car to see if the same thing happened with the tiny metal (+) tab. But not today.