FOB battery replacement - how & when

I just finished taking photos of how to do it. They'll be added to the User-Guide shortly.

$3.49 was how much the battery (CR-2032) cost.

A teeny-tiny (#0 size) jeweler screwdriver was the only tool needed.

The entire process took just a minute.

I had to do it twice though, as I made a discovery along the way and needed to confirm my hunch. Sure enough, Toyota provided a clever way of being able to easily check the status of the battery... or you can just wait until the car itself starts telling you (by beeping, flashing a warning, and not always responding). I didn't realize this feature was available, since I rarely ever actually see the thing while in use and it took 4.5 years for that battery to wear down.

Anywho, press any button on the FOB and watch what happens. The mini red light in the upper-right corner will no longer illuminate if the battery is running low. Interesting, eh?

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keep us posted when you added the new manaul part
great work!

There's a new illustrated page for this now available in the User-Guide.

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Just a word of advice - the degree of ease with which the back cover comes off (the one with the Toyota emblem) varies, and it can be very difficult to very easy. If it is very difficult, you aren't necessarily doing it wrong, but it will take strength and care.

Thank you for making the user guide!

Tip for opening the cover:

First note that the cover slides along and parallel to the body of the fob; it does not pop perpendicularly away from the body of the fob. Keep in mind that the mechanical key release slider must be operated in order to remove the cover. And indeed it can be difficult to get enough purchase on the cover with fingers alone to get it to start moving.

Now: after the mechanical key is removed you will see a small beveled tab which moves into and out of the key space as you move the key release slider. This tab retains the mechanical key; the entire mechanism is part of the cover, not the body of the fob. Notice that there is a small space behind the tab (that is, on the innermost, non-beveled face of the tab), between the tab and the body of the fob. If you insert an awl or small screwdriver (but not as small as the #0 to be used later on the battery cover screws) into this space you can gently force the tab away from the body of the fob and so start the cover sliding off the fob body. After the cover moves just a little it should easily come off.


If like me you ever use only one fob you might move the battery from the unused or spare fob into the used fob. I did this to suck the life out... err, that is, to extract the value from the second battery (now four years old) before buying a new battery.

Thanks for the link and info as my fob battery died this morning. The problem is that the force used to move the switch is against the way the cover needs to slide. Here is the trick that I used to get the cover off:

Right near the switch there is a lip on the cover. I used my teeth (too slippery for my hand) to push the cover up (without touching the switch). This caused the cover to move up a tiny amount. At the non-switch end, I was able to put in a nail file in the tiny opening. Then, I could use my hand to move the switch and with the nail file at the other end, the cover slid off easily.

My fob lasted 4.5 years with the original battery. Also, the CR-2032 batteries were $4.50 for a 2-pack at WalMart so will probably replace the other fob battery tonight.

I find it easy to open after some trial and error.

1. Take the key out. Not necessary, but it seems a LITTLE easier to slide the cover with it out. It will come out when you take the cover off anyway.
2. Hold your right hand, palm up, in front of you, fingers flat. Put the fob in your right hand, emblem up in a position that places your thumb between the emblem and the end of the fob (at the top of the Toyota stylized T) and the fob on your flat middle and ring finger. The key side of the fob will be facing you, the release will be to your left
3. Put your left middle finger on the side of the fob away from you and your left thumbnail on the release
4. Push the release away from you with your left thumbnail and push down on the cover with your right thumb, then push toward your left hand.

Pushing down on the far end of the cover seems to make all the difference, it slides off easily.

Probably not necessary. My SKS equipped car started flipping me the 'no key' signal when I was sitting in it WITH it turned on when a passenger opened a door to get out. The 'no key' indicator went out a little while after the door was closed. I figured it was a hint and replaced the battery. I tested the old one: 2.62V I also tested the one in the spare fob (RARELY used, just sitting in the desk drawer sending out its 'here I am' signals), 2.82V so it should be good for some time to come.

My car is just over 4 years old and I almost never use the buttons on the fob. So little in fact that I just realized there is a small tactile nub on the lock button I don't know if using them frequently uses more battery power and would necessitate an earlier replacement.

I actually have a spare new battery now as by mere coincidence, the bathroom scale uses the same battery and gave me a 'Lo' reading last week (I presume it wasn't talking about MY weight). I figured if I had to get a battery for the scale, I might as well get one for the fob at the same time. Thinking the scale probably uses more power and the battery would still have life left for the fob, I put the old battery in the fob and it worked fine. Tonight when I tested the removed fob battery and the battery in the spare fob, I also tested the one I took out of the scale and put in the primary fob. It read 3V. SO, I'm not sure why the scale was complaining, it only has the one battery.

I just replaced ours. Oddly enough mine completely failed first, and my wife drives the Prius every day I drive it maybe once a week. I do use the lock/unlock buttons out of habit since my Lexus doesn't have SKS...maybe that is why.

Her key was easy to slide because since it never leaves her purse it was in almost new condition. My key is on my keyring and goes in my pocket, so its all beat up and the plastic finish is smooth, etc. Mine was almost impossible to slide off.

I used one of those rubber jar openers to get traction and slide the cover off, worked great.

Your computer's motherboard uses the same battery!

This has got to be the best user forum site I have ever belonged to. It is head and shoulders above the usual sites: informative, topical professional level in all respects and, most importantly, its members are equally awesome.

One minor quibble from one who has had few or no problems with his 2003 Prius. Not everyone is up to date with the gazillion acronyms and abbreviations tossed about.
Hoe about a little mercy for the rest of us? An occasional hint would really help.

I'd also suggest the instructions on Tom's site as well: 2004 Prius Keyfob Battery Change

My key battery also died after almost 5 years. I followed instructions to install a new battery but couldn't get the cover off no matter how hard I tried. I took it to West Ashley Toyota in Charleston and the service manager couldn't open it either. The parts worker succeeded finally after 15 minutes of tool and strong hand usage. They did not charge me.

Agreed, the cover can get stuck on pretty good. Note that the cover slides off parallel to the long axis of the body of the fob; then, after removing the mechanical key it should become apparent where one can pry at the cover through the newly-exposed space with a small screwdriver or awl to start it sliding.

Another way to get that pesky cover off --
View the pictures in order along with the text:
Addendum: (The series is 7 pictures. At the moment I seem limited to 3 at a time. I'll add the others if possible).

P1:The tool. An even smaller phillips is needed for the screws.
P2:The key has been removed. Orient the for on it's side on a table. The Toyota logo is on the right.
P2:Rotate 90 degrees counter clockwise. Now the buttons are anterior.
P2:The key latch is not depressed, and juts upward.
P3: Key latch is depressed, and is flush. But now an opening is available to stick the screwdriver into to push the cover off.
P4:I use the finger on my right hand next to my pinkie to press on the fob so that it does not move, depress the key latch with one of my left hand fingers, insert the screwdriver and push to the left. Be sure to hold the key latch down completely.

Even though I could not slide the cover off for the life of me the usual way of just pushing on the cover with my thumb, this way is easy on both of the fobs I switched batteries on. Typical of Toyota, the fob is put together very precisely. I tend to think that this method is just moving the cover a tad in whatever direction is needed to avoid a block.

John

Good writeup. I'd like to add it's really important to spray lock lube into the driver door cylinder, and use the emergency key to turn the cylinder, twice a year

Last year when my fob battery finally got weak, I thought I'd try the emergency key to see if it worked. Had never used it before and the cylinder was VERY stiff. Sprayed lock lube into the keyhole, that made it much better

Taking advice from PC, I bought two leather Zippo cigarette lighter cases (holsters, scabbards, whatever) at Walmart (about $7). They exactly fit the fob. The glitch is that as I was buying them, I discovered that Walmart was discontinuing them. I talked to an assistant manager about the possibility of restocking them in automotive, and she said they'd look into it. Haven't seen any results. I found them at a tobacco store, but they were more than twice as much, maybe $20.

Anyway, we never take the fobs out of the the cases and of course never use the buttons. The fobs seem to be new-looking (it's been so long, I can't remember if they were really shiny). My wife and I both carry our own, even when we're riding together. It will be interesting to see which goes first -- the fob battery or me.

Anyway, I appreciate the suggestion about lubeing and using the door lock once in a while. I'll do that.

Does the car beep when you shut it off to indicate low fob battery? That is happening to me now (2005 Prius) And where can you get replacement batteries? Thanks!

Yes.

Any drugstore, CR2032, should cost ~$5 or less.