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91ls400

Replace The Battery In Remote Key

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My master remote key for my 1991 LS 400 has stopped working. I think that the battery in the key has died. I took the little screw out but the key wouldn't come apart. Does anyone know how to take apart the key and what battery it takes.

This is the only master key that I have so I don't want to ruin it!

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Check first to make sure you haven't accidentally hit the remote off switch on the instrument panel. Twice, my wife thought the battery in her remote was bad and I found the switch turned off.

Curt

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No its not the switch. I even asked the Lexus dealer to make sure the switch worked, unfortunately I didn't have the master key with me at the dealership. But they said the switch was working fine.

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I thought that as well when I first bought my LS400. The remote key was not working. I was on my way to get a battery for it when I noticed the "remote" on-off switch on the instrument panel. It was off- so I switched it on and now it works perfectly.

About your key - did you try to "pry" on it a little?

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I just changed the batteries on each of my keys for my 99 LS.

Yeah,

Just had to pry a little, work it with a jewelers screwdriver (flat). BTW, called lexus just to get a price for battery and they wanted $13 each!! It was jus a panasonic brand so I went to WALMART and paid $2.89 each for them.

Once I got the top off, the battery was in another sealed cap area - so had to unscrew 2 phillips to get the battery cover off.

Clean it up while the cover's off - lots of little lint and dirt gets wedged in the key.

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I got the key cover off of my key with a flathead screwdriver, per suggestion, I tested the battery and it still had a charge. The switch in the dash is ON. Is there anything else that could be wrong, like, something in the key, a blown fuse, or something else?

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I got a new battery for mine at Radio Shack for about 3 or 4 dollars. After I took the little screw out, I just popped off the cap with a small screwdriver.

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if you have replaced the battery inside the key & the inside switch is on & it still doesnt work, then it looks like you have a dead circuit board inside the key....They are very expensive to replace. - A couple of hundred dollars or so...

Jeff

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I went and got a new battery and the remote worked once or twice. About an hour later the remote wouldn't do a thing. I press the button, regardless of where I stand nothing happens Could I have blown something, please help!

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No 91, I don't thinks so. Since I din't know anything, I took the screw out and the thing wouldn't come apart. I then pried it and the cover popped off. It had one of those little round batteries which I took to Radio shack. I put the new one it and it has worked fine ever since. I did notice a lot of ship in there so when I got home, I opened it again and cleaned it out with a small brush and a Q-tip with rubbing alcohol. Still works great. First, make sure the battery you bought was good. I have bought watch batteries that were bad before. If it still doens't work then you might have another problem. By the way, the reason I replace my battery was because it didn't work. As soon as I flicked the remote switch back to "on" it worked again. I guess I hit it cleaning.

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I started this thread long ago, but I got new info! My key remote worked twice today then stopped. I heard that to test your key, tune to 94.4 on your radio and test the key, if it work the radio will cut out or have interference(only 1st gen). According to this test my key works! Where is the receiver for the keyless entry system, I have heard in trunk but how do I access it?

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Can't help you with that buddy, maybe someone with a manual could look it up. My guess is that it is uder the dash somewhere, but I don't understand how it functions so it's just speculation.

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On my 90 LS, the receiver for the keyless entry was behine the trim panel on the left wall of the trunk; the antenna for it was in the rear window. My keyless entry worked the last few years only when the weather was below freezing. There is a diagnosis procedure in one of the repair manuals, but I passed the manuals on to the new owner last year. I performed the diagnostic procedure on the receiver in my 90 and it checkout as being OK so I assumed that the problem was which the dash switch. I especially thought it was the dash switch because in zero degree weather, the keyless entry would continue to work if I did not turn on the heater. The keyless entry never worked 100% in my 90 even when new. The receiver and keys were replaced several times under warranty and there were several shopping centers where the keyless would never work -- the dealer thought there might be interference from the shopping center security system.

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I was looking in my trunk this morning, if you remove both mats so that you are down to just the spare tire and bare metal. On the extreme drivers side on the floor of the trunk there is a removeable panel. Once I removed the panel there was a black plastic box, and group of wires running there. Is the black box the remote entry reciever? I couldnt get any of the other other side trim off, it seems to be glued in place. Any one with a manual please help.

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91, that sounds like the box you are looking for. I remember that it was not very big although apparently I forgot exactly were it was located. I remember that one end of it had a slot through which the master key would be inserted during the diagostic procedure.

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Hi all,my car was a uk bought mk1 LS400 1991 model.I also replaced the battery in the key,ive checked and the remote button is on,on the dash.Mine also does not work even with a new battery.The test you can do is,with the doors door open lock and unlock the car with the main switch on the door trim,MAKE SURE that the door light is on and working,thats what turns the door ecu on.So to recap,door open lock and unlock the doors about 10 times making sure the locking unlocking fully,the doors should then lock and unlock once on there own,with in 1 or 2 secs press and hold the button on your key.The doors will then lock/unlock between 1,2 or 3 times.I will have to dig up the paper work to find out which each means,done this test on my car the other week and it said the key was not the one for the car.So im in the same boat as you guys,the cheap fix for me is that the car only has its factory alarm,so for the price lexus want to fix it i will get a car alarm fitted that will lock/unlock for the same sort of price...

The other post about tuning the radio in also tests if the key remote works..good luck :)

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