Yaris 2002 key fob only works once after battery replacement - help

[angaaruriakhil]

Hi all, 

I've got a peculiar issue with my second key on my Yaris 2002. I was recently clearing up the house and found my spare key which hasn't been used for years. I figured the Battery was dead after all this time. So I bought a new pack of Energizer CR2016 coin batteries, opened up the key and replaced it.

So after replacing it, when I press any of the buttons just once, there is an LED response the first time. But after that, if you press a button, nothing happens. If I remove and replace the Battery, again, the LED on the fob only displays once when you press a button, then never again on subsequent presses. Interestingly, the car doesn't unlock at all, even during the first press. I looked at the board and couldn't see any corrosion or anything, the thing looks spotless. Using the key manually works fine and is able to start the car also. 

Did a bit of googling and couldn't find anything. Hence, I am asking here. Could anybody kindly suggest a solution? Any help is appreciated. 

[Cyker]

Are you sure it's not a thin layer of corrosion on the Battery contacts? Maybe give them a little scrub with something slightly (but not too) abrasive or a wipe with some switch cleaner fluid?

[angaaruriakhil]

11 minutes ago, Cyker said:

Are you sure it's not a thin layer of corrosion on the battery contacts? Maybe give them a little scrub with something slightly (but not too) abrasive or a wipe with some switch cleaner fluid?

I've brushed the whole board with 99.9% IPA and its still behaving the same unfortunately. 

[Cyker]

I only ask as the old lithium cell might have leaked and corroded the contacts a bit. Often when putting in a new Battery, it scrapes the surface just enough to allow some contact, but without a more thorough cleaning it's not enough and there's too much resistance.

I had similar behaviour with the franken-key I had, due to the key cutter super-gluing a cloned RFID chip into the key because they couldn't get the car to accept the one built into the 'eBay-special' I'd bought. If you've ever seen Beverly Hills Cop 2, it turns out the super glue trick is real, and when I took it apart to find out why it'd stopped working there was a misty residue all over it, including a very clear fingerprint on the clear Battery cover and coin cell!

It took a bit of scrubbing with a scouring pad to clean it all off but the key worked fine since...

 

Otherwise I'm at a loss and will have to bow out and see what everyone else thinks - Normally those keys are pretty robust - I've dropped my Mk1 and Mk2's keys so many times and they never had any problems!  

To my knowledge there aren't any common issues caused by a key not being used for a long time, aside from the aforementioned corrosion on the contacts...

 

[angaaruriakhil]

43 minutes ago, Cyker said:

I only ask as the old lithium cell might have leaked and corroded the contacts a bit. Often when putting in a new battery, it scrapes the surface just enough to allow some contact, but without a more thorough cleaning it's not enough and there's too much resistance.

I had similar behaviour with the franken-key I had, due to the key cutter super-gluing a cloned RFID chip into the key because they couldn't get the car to accept the one built into the 'eBay-special' I'd bought. If you've ever seen Beverly Hills Cop 2, it turns out the super glue trick is real, and when I took it apart to find out why it'd stopped working there was a misty residue all over it, including a very clear fingerprint on the clear battery cover and coin cell!

It took a bit of scrubbing with a scouring pad to clean it all off but the key worked fine since...

 

Otherwise I'm at a loss and will have to bow out and see what everyone else thinks - Normally those keys are pretty robust - I've dropped my Mk1 and Mk2's keys so many times and they never had any problems!  

To my knowledge there aren't any common issues caused by a key not being used for a long time, aside from the aforementioned corrosion on the contacts...

 

Thanks Cyker. Your comments on contact made me think that maybe the metal prongs weren't contacting the Battery and board well enough. I bent them around with needlenose pliers so they'd contact better on both sides, but no dice. Same symptoms. When you pop the Battery in, it works once and then refuses to work again until Battery is taken out and put in again. AFAIK this key hasn't been apart before, everything looks stock like in my other key. It looks spotless so it's really perplexing. I did some probing with the multimeter and the resistors are all their reported values. The switches also have no continuity until the button is pressed. 

And yeah, Toyota stuff is usually reliable in general! That's why I love them. I have no idea what's going on here though 😕 

[Cyker]

Drat... I can't think of what to check next... maybe flash22 will have some ideas???

[flash22]

Did you peel the film off the Battery ? Did you test the remote out of the housing ? Be careful not to lose the passive immobilizer chip, I take it you cleaned the rubber membrane and the buttons are moving freely ?

I Know Nothing....................

[gezhenry]

I've got a similar issue with a spare set of keys new Battery with voltage, contacts seem ok clean and contacting, but the buttons despite having been externally cleaned not responding (and don't seem to 'click')

 

Can you replace the 'buttons' on fobs? Are they integral with the circuit board? Or is it just the rubber cover membrane that gets changed or otherwise?

[Cyker]

Should be doable as long as you can use a soldering iron and have a steady hand; I've seen people sell kits on eBay with replacement rubbers and buttons etc.

 

[stantheman1]

It sounds like you could have a weak or faulty Battery, are you 100% sure you're trying it with the 'new' Battery? Try swapping the Battery for the one in the working fob to rule that out.

[corradovr6]

just for info, i bought some 'new' panasonic button cells.  Installed them thinking they were new but none, absolutely none, of them worked.  Checked with a meter and they were all dead.  Bought them 1 year back so couldn't do anything.

 

So as above, i would check your Battery and see its ok.  Also, clean the contacts with something slightly abrasive, even a small screwdriver to scratch the contact areas gently.  I think the prongs should generally be ok so perhaps no need to move them, but check they are making proper contact.

 

The switches - well you can desolder and replace, but i'm not good enough with fine soldering!  Try spraying the board with an electrical contact cleaner and see if that helps too.  Best of luck!

 

Edit: Just checked that Cyker has suggested pretty much everything i said...i'm a bit late to the party!

[Cyker]

It's nice to have some confirmation/reinforcement!  

[bathtub tom]

I've had problems with buttons before, and if a good clean doesn't do it (both sides of contacts), I've used a hole punch to punch some circles out of kitchen foil and super-glued the less shiny,tiny circles onto the non-electrical side of the problem. I've a telly remote that's working well with such a solution (for now, fingers crossed etc.).

[angaaruriakhil]

Thanks for your suggestions all. I tried everything (batteries measure OK on multimeter, contacts are cleaned thoroughly w/IPA and a brush, buttons are clicky and respond on the first click, no film on battery) but it still has the same symptoms. I'll try the aluminium foil trick later (as suggested by Tom), but if that doesn't work I think I'll just have to hold a funeral for this fob and move on with my life. 

[angaaruriakhil]

Just posting a resolution for anyone who wanders here from a google. My issue was that corrosion (from water damage) had destroyed one of the small via's on the back of the key PCB, hence the irregular behavior. I overlooked this in my analysis as they are so small, I should have looked more closely. I ordered a replacement PCB and soldered the small flash chip onto the new board. Works now. 

[Cyker]

Wow that's a bit more involved than I'd hoped for but kudos for figuring it out and managing to repair it!

Thanks for coming back and letting us know how you got on too