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(17,805 posts)
Fri Apr 5, 2024, 06:36 PM Apr 2024

UPDATE: 2008 Prius fob replacement questions

I went out to start my 2008 Prius today, and it was dead. I used the metal key to open the driver door. The car wouldn't turn on. I noticed that the passenger door wasn't closed tightly, and would have been like that since Wed., so it's possible the 12 volt battery is dead (not the hybrid battery). Both fobs are in terrible shape, the button covers are gone. I have meant to replace, but it is one of those things that I forget as soon as I get in the house. I thought I'd try changing the battery in the fob, and then trying it in the car again. I got the battery changed and tried it, but It didn't unlock the door or start the car. I will get a charger set up, tomorrow, when it's warmer, and try charging the car battery, but I have a couple of questions about the fob, and if anyone could offer advice, I'd appreciate it very much.

Since I switched out the battery, will I have to reset the fob for the locks and ignition to recognize it? Or will the fob work without resetting if the battery in the car is charged back up?

Next, I will order new fobs. I was looking and I see fob shells that are identical to my fob. But if I get a shell, does that mean the the electronics inside the fob I've had all these years needs to be transferred to the new shell? Will the new fob have to be reprogrammed? I saw and watched videos on how to set a new fob, but not sure the routine will work on a fob that old. Can I get a new fob that has its own electronics inside and just have my mechanic program it?

I'm proud that I changed the battery, but I wish I would've thought ahead about the car recognizing the fob after a battery change.

That's where I'm at. If anyone can offer any insight, thank you!

I found my portable charger, the long extension cord, got the lid off the fuse/relay box under the hood to access the quick charge feature, and as of right now, the battery is charging. The hardest part was getting the lid off the relay/fuse box and next hardest was finding the charger. I set the charger on the 2 amp charge, but just read that 10 amp is also considered slow charge, so I think I'll change the setting.

Thank you!

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UPDATE: 2008 Prius fob replacement questions (Original Post) Marthe48 Apr 2024 OP
You can buy an empty shell FreeForm73 Apr 2024 #1
The 12 volt battery is pretty new Marthe48 Apr 2024 #2
You're welcome n/t FreeForm73 Apr 2024 #3
I've got a 2007 Prius Eyeball_Kid Apr 2024 #4
That's good to know! Marthe48 Apr 2024 #6
No and NO. I suspect your 12 volt battery is dead. Call AAA--they can replace it,no problem. hlthe2b Apr 2024 #5
I don't know but here is a video? mockmonkey Apr 2024 #7
I watched 3 videos Marthe48 Apr 2024 #8


(45 posts)
1. You can buy an empty shell
Fri Apr 5, 2024, 06:42 PM
Apr 2024

and transfer the electronics. You will also need a new 2032 battery
The 12 volt battery will go just like that
You may just need those new shells, I got mine on eBay, not expensive at all


(17,805 posts)
2. The 12 volt battery is pretty new
Fri Apr 5, 2024, 06:45 PM
Apr 2024

But I can have the mechanic check for me.

The shells I saw were on Amazon, just what popped up on a Google search.

Thanks for the clear advice.


(7,497 posts)
4. I've got a 2007 Prius
Fri Apr 5, 2024, 06:48 PM
Apr 2024

Several years ago, I had a FOB problem. I'm trying to remember how it was solved...

First, I remember having a refurbished FOB from an eBay seller and doing a number of tasks with the ignition and the driver's door to get the refurbished FOB to copy the identifying information into its storage. You can find this information on the web. It's a little confusing at first. Anyway, I got the FOB to work about 7 years ago, and it's still working.

Second, the battery should have no bearing on the wireless link between the car and the FOB. I've had my battery disconnected a few times and never had a problem with the FOB. Further, on my second FOB that I got from the dealer during purchase, I swapped a FOB battery for the old one, at the service counter and the FOB worked fine after that.

Good luck.


(17,805 posts)
6. That's good to know!
Fri Apr 5, 2024, 07:12 PM
Apr 2024

I would have charged the 12 v. when I realized, but it is cold and drizzly, didn't want everything to get wet. I will follow up, I hope tomorrow


(103,313 posts)
5. No and NO. I suspect your 12 volt battery is dead. Call AAA--they can replace it,no problem.
Fri Apr 5, 2024, 07:12 PM
Apr 2024

Once you do, your fobs with their (assuming functional) new batteries will work.

I should mention that if your 12 volt was totally dead, you will have to drive around for about an hour before your electronics reset. So, don't be alarmed if once it is started your onboard monitor screens are all screwed up. They will reset.


(2,929 posts)
7. I don't know but here is a video?
Sat Apr 6, 2024, 12:29 AM
Apr 2024

Directions if you don't have keyless ignition.


I remember having to do something like this for my Ford which involved turning the key on and off about 10 times.


(17,805 posts)
8. I watched 3 videos
Sat Apr 6, 2024, 08:29 AM
Apr 2024

yesterday to try to diagnose the problem. I bookmarked the ones I think will help. When I get back to work on the car this morning, I'll check the manual to see if there's anything about the fob in there.

I'll watch the video you shared after I've had more coffee

Thank you!

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