Lexus IS key fob issue

Hello everyone.

Every two years I replace the key fob battery myself without any issues at all but this past week, after replacing the battery, the key fob isn’t operating like it should.

The problem is that it won’t open the trunk without physically using the key job after the car sits over night.

When I walk up to the trunk, I only need to press the trunk released button while the key fob is in my pocket and the trunk would open.

Now, it only opens after using the key fob and after that I can open the trunk without the key fob for the rest of the day.

Once the car sleeps over night, the trunk won’t work without using the key fob physical button.

This is weird because the battery is so simple to replace and I did this twice before now without any issues.

Thank you in advance for your help. Much appreciated.

Modernity strikes yet again! … lol … Sorry, no idea how to solve that. If I were on a desert island and had to solve it myself (for some reason) I’d try resetting everything by disconnecting the battery (both the car battery and the key fob battery ) overnight. Be forewarned however that doing this can cause other problems you don’t want, worse than the trunk problem.

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The vehicle is locked overnight, and the trunk lid button does not respond while the doors are locked, correct?
Do the doors unlock when you touch the exterior door handles, or do you press a button on the key?

Everything else works fine but the trunk.

So, the car will unlock in the mornings when I touch the door handle just fine. The trunk, however, won’t open unless I press the release button on the key fob.

Before the battery replacement, I never needed to use the key fob for anything except to be presence on me at all times.

You know what I’m thinking, Nevada_545? I wonder if the trunk button needs to be lubricated ? Maybe the trunk release button is the problem rather than the key fob? And it’s just a coincidence that after replacing the battery the trunk is acting up?

But then again, I wonder why the key remote would open the trunk if the lock is stuck due to dryness ? Because when I open the trunk using the remote, the lock seems to unlock precisely.

Maybe the key fob has a stronger punch than the trunk release button ? I’m just speculating. I wouldn’t know how to lubricate the trunk lock, either.

If I understand this correctly, the trunk lid button works for the rest of the day because the doors are unlocked. The trunk lid button does not react while the Smart Key is close to the trunk and the doors are locked.

There are two systems involved: the button on the key sends a signal to a receiver inside the car, Smart Key operation (proximity) relies on a sensor under the bumper cover.

You can verify the operation: lock the vehicle, wait 30 seconds and try the trunk lid button while having the key less than 3 feet from the trunk. If the trunk won’t open, the key battery may be weak or Smart Key access might be turned off.

I will do this in the morning to verify. I recently walked inside the house.

Thank you.

Well check to make sure the valet button has not been pushed. I spent an hour diagnosing a similar problem with my olds only to find the valet switch activated. No one owned up to it.

The other thing is, if you have had the fob apart, you know how flimsy the buttons are and they do wear out. I’ve had to replace mine already. I bought two oem on line for about $100 and the dealer programmed the for another $100. Only genuine oem though. Or check your work with a fresh battery.


It seems this was the culprit, Bing. The valet button was pushed and I know my mom won’t admit to it. She has a thing for aggressively pushing buttons harder than necessary.

I was fixing to reply to Nevada. The trunk released without issues this morning but that’s because I freed up the valet button yesterday. I repeatedly push the trunk button in hopes it would get rid of whatever was causing it to stick.

What can I say: I’m happy it’s working again ( at least for now ).


When the trunk cancel switch is on, the trunk can’t be opened using the remote, but you stated the remote was working.

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I’m thinking valet button is the button on the trunk ?

I might be misunderstanding the terminology here of what a valet button is.

Yesterday I repeatedly pressed the trunk button and closed and opened the trunk to help it from sticking.

Today it’s working fine.

Thanks a lot for the picture you posted here. I had no idea my car had this button in the glove box.

I expect that’s a button you push on modern cars before handing the key to the valet when arriving at a valet-parking restaurant, etc. The valet has the key to drive the car, open and close the door, but isn’t able to open the trunk with that key when the button is pressed. So you can put anything valuable in the trunk and not have to worry the valet might steal it. There’s other obvious risks* involved w/ using a valet, but at least with that button they can’t open the trunk.

  • For example, as seen in the movie “Ferris Bueller’s Day Off” … lol …
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See, George, I’ve learned so much from you guys on here. I’m really appreciative of the support I receive on here from the helpful ones like yourself.

After you explained to me what valet button is, I went around asking my family members what a valet button is. I wanted to know if anyone in my family knew the answer, and just like I predicted, no one knew. lol. And my family isn’t dumb as most of us are in the medical field. Lol.

So I showed them where the valet button is located on my car, and they were like “ who cares.” I told them I care because I want to learn about cars :grin:

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