Key Fob Batteries

[Denny413]

I used my spare key fob a few months ago for my 2010 LS and the battery was dead. I bought a battery at the drug store, installed it, and the next day it was dead. Thought it was a bad battery, so I bought another, which died the next day. Since then, my Lexus dealer has installed three more batteries, the most recent was yesterday (1/14/14) and they have all died in one day.

It is not kept near anything that would emit a ping and drain the battery.

I think the fob is bad and my dealer insists they never go bad.

Anyone else have problems?

[Jeff in TX]

So, how are you determining that the battery is bad?

[LEXIRX330]

What could possibly draining the batteries that fast. Even if you held down the button continually I can't see it draining the battery in a day.

[Denny413]

Jeff, put a new battery in today, and the fob works. By tomorrow, it is completely dead. My other fob hasn't had the battery replaced in over a year, and it is in the same pocket as my phone.

[Jeff in TX]

Denny,

I am trying to determine how you know the battery is "dead." Are you measuring it, the key battery, with a voltmeter?

[Denny413]

Hi Jeff,

I have now installed 6 batteries (2 from the drugstore) and four from my dealer. The fob will work for one day. After a day, it will not unlock the door, even with the fob against the handle. It's dead.

[Jeff in TX]

There is a lot going on with these devices and to assume that the battery is bad when they don't work may not get you anywhere. The only way to determine that the battery is dead is to remove it and test it with a voltmeter. Do you have another electronic key that works? Are you just concerned about the touch-open feature or is it that you are unable to start the car except with the emergency procedure?

The technology that is employed to enable this process employs Radio Frequency transmitters and receivers. I suspect that what is happening to you is that there is an interfering RF signal at the location where you start your day. An example of how this can occur and seem to be time-of-day dependent is a defective sodium vapor night light. Let's say that the defective light is generating broadband noise that interferes with the key operation and that the light is only on in the morning. That may make it seem that your key battery has been discharged overnight. There are many possibilities regarding Radio Frequency Interference sources such as defective cell site transmitters, defective motors, Radio Station transmitters, arcing power lines, defective fluorescent or sodium vapor lights, etc. Most of these interfering sources only propagate a short distance at levels that cause problems so you might evaluate this by seeing if your car works okay at a different location such as a friends garage.

[Denny413]

I know that you are trying to help, and I appreciate it. This is my spare key fob. The one I use every day works fine. I just took the "dead" battery out of my spare key fob and put that battery in my every day fob. The battery is dead.

[Jeff in TX]

Thanks, I understand. Your electronic key is defective!!

[Denny413]

Now if I can convince my dealer...

[Jeff in TX]

If what seems to be happening is really happening, then you would need to take your electronic key to the dealership and have them put a new battery in, take it out to your car and demonstrate to them that it will operate your car. Leave it, the suspected defective electronic key, at the dealership for two days (an extra day for good measure) and then ask them to go out and demonstrate to you that it will operate your car. That should help move your case along one way or the other.

[Denny413]

Thanks Jeff.

[pj8708]

Hi Dennis and welcome to the Club!

I want to offer an additional check to make sure your dealer is on the right track. Not that I think he's in error, but I think you might feel better if you had an opinion from one other source.

There is a Lexus dealer in Dallas, TX. Sewell Lexus, who does a large volume of business selling new Lexus parts. A few months ago, I lost my spare fob for my 2013 ES350. My local dealer wanted $320. for a new fob. Sewell had the same part for $160. Part of the reason for the huge difference is that when you sign-on to Sewell's web-site they ask if you belong to this Club or others. Just check yes and you'll get an excellent discount.

You can order on-line from Sewell and also talk to one of their Customer Service people.

You may have a problem with the software program in the fob, and in fact that may be why your battery is draining. It maybe locked in an "ON" position all the time. If you buy a new fob, your dealer will have to program it for you. No sweat. It's only around $35.00.

Come back and let us know whats going on!

Paul Sewellparts.com