Wednesday, 23 May 2012

How I Fixed my Broken Toyota Prius Remote Key Fob

When I bought my Prius from Hodgsons Toyota in Gateshead last year I remember asking if there were two keys with the car.  I had, after all, been stung by this in the past and I had no wish to once again own a car with only one key.  Yes, came the answer, there were indeed two keys.  Good I said.  Later, once I got the car home I said something different.  I won't repeat it.  Not on this blog.  One of the two remote key fobs was not working.  I could lock the car with it, and drive the car with it, but I could not unlock the car with it.  Naughty them.  As a used approved Toyota, one would expect every aspect of my car to have been inspected and checked, including the key.  You cannot, after all, use a car without one.  Perhaps keys just don't feature in their checklists.  I'd love to know if others have had a similar experience, or indeed if anyone knows of manufacturers who include inspection of keys as a standard checklist item for a used approved vehicle.  Please leave a comment below if you have any stories.  I am sure others as well as myself would love to read of such experiences.

Right, back to my poor wee broken Prius key fob.  Something didn't feel right with the unlock button, in a tactile sense I mean.  It was as if something had been knocked out of place within the inner mechanism of the button.  I didn't know anything about the structure of the key fob.  Google is my friend, however, and after a little digging about on the web I figured out a plan. Now it is worth mentioning that my remote key fob is not a smart (SKS) type - just the plain old standard key fob.  I am sure the technique I used will be good for both.  Without further ado, here is what I did.

  • I got a scalpel knife, like the one shown below.  Make sure the blade is as razor sharp as possible in order to get as clean and neat a cut as you can.

    • Put the remote key fob on a hard flat surface with some protection in place.  You don't want to damage a table if the knife blade slips.
    • Make a cut with the knife as shown in the photo below.  This is just to break the seal between the rubber membrane and the hard plastic case.  Note: it was the unlock button on my key I was fixing.

    • With just enough of the rubber membrane cut neatly along the seal between it and the hard plastic case, peel back the rubber membrane to expose the inner button mechanism.  Each button has a hard white plastic microswitch - square in shape - fixed onto the circuit board.  There is a circular 'plunger' at the centre of each microswitch.  On my key, it was this that had been knocked out of alignment with its recess in the rubber membrane above.  Gently tease the circular plunger back into alignment using your finger or tweezers.  Test that the circular plunger by pushing it down.  It should click. (You might even wish to test it by carefully taking it near to your Prius and checking if the door unlocks.)
    • Now you are sure the unlock microswitch is working, carefully replace the rubber membrane.  Ensure the recess within the rubber membrane covers the circular plunger of the microswitch correctly.
    • Lastly, apply some Loctite / Superglue to the edge of the rubber membrane and the plastic casing and glue together.  Keep fastened in place while the glue cures by applying masking tape or equivalent.
    • Congratulations!  Your key should be fixed and ready to use.

    I now have a fully working remote key fob and it was fixed with standard household items.  It has never come apart and always works when I use it.  Incidentally, it was the same key that I used to take the photo above.


    1. I've had three of these "smart" keys break in exactly this way--open button died--on me. The first broke after 2 years and was replaced as a courtesy by the dealer, the second broke 2 years later and sat in my drawer as a spare until the third just broke yesterday.

      After finding this post I tried the membrane slit trick and it works like a charm. Two comments: I slit so little that I can't get any super glue in there--apparently I slit from the correct side so that the knife knocked that plunger back into position without any fiddling. Also, the broken plunger on mine had worn out the battery in short order, so I have had to replace the CR 2032 batteries. This is an easy do-it-yourself: slip out the hard key by pushing the lever on the top to the side, then push the same lever again to remove the entire back place in the same direction. Four tiny screws hold the battery plate down. YouTube has a video showing how to do this.

      Thanks very much Sean for posting this!

    2. Hi - I'm so glad this post helped you. Tells me that there must be something of a design fault if the key fobs systematically fail like this. I hope the plunger stays in place for you without gluing the membrane back. If you did need to get glue into the slit to cement it back together perhaps squeezing a blob of glue onto, say, a piece of cardboard then taking a pin and dipping it into the glue might provide a means with which to teeze the glue into the slit. Interesting, too, to read about your problem (and solution) with the battery. In the meantime, you are very welcome and I'm chuffed you've found this blog useful. Best regards, Sean.

    3. Thanks for the post! I just did mine. However, I used a very sharp knife and stabbed on the side to lift the rubber. I simply snapped the rubber back in place. It didn't look like it'd need superglue but I'll apply a dab of electronic sealant to prevent moisture from circuit. Thanks again!

    4. You're very welcome ... and I'm so glad it worked for you. Yes, probably prudent to apply a sealant of sorts between the membrane and casing. How many times have you dumped the car keys on a table splattered with spots of coffee or on the kitchen worktop covered with all sorts of liquid, gravy, sauce etc? So easy for fluid to seep in and contact the delicate electronics. Best regards, Sean.

    5. This totally works. My problem was that the rubber had snapped though and was keeping the clicker pressed. SO once I slit it, the clicker popped back and I kept the cover loose and used a little silicone to seal it. I fixed 2 of them this way. They work like new. Saved $800.
      This is how I did it:

      (1) Prepare a safe well lit work space. Take out battery.
      (2) Carefully slice rubber with a scalpel or modelling knife. Important to put cap back on knife when done, have good lighting, no kids around, reading glasses if necessary, etc. In my case the clicker was fine on both fobs. They popped out right away.
      (3) Use slight sealent and work along slit with toothpick.
      Wipe off excess. You don't want big gobs of sealant hanging off of it. Also you should wear safety glasses when handing any type of sealant or adhesive. You should wear gloves too.
      (4) Put everything away in its proper location and safely out of reach of children.

    6. Worked like a charm, just in time to leave my fob with my sister for the holidays so she can use my car! THANK YOU. I really didn't need a $300 expense at Christmas on top of everything else.

    7. Great info - my problem is the rubber cover is missing. The buttons click when you press them. When I replace battery, it works for about 2-3 days, then automatically locks/unlocks on its own, then dead again. Any suggestions? As I said, the rubber cover over the buttons is gone.

    8. Hi Rebecca, that is a problem, isn't it? My information is that the rubber membrane is not a separately orderable part. You would have to buy a whole key fob. However, don't despair! Cheapest solution might be to get a thick tape (gaffer tape here in the UK - the kind with a woven fabric backing) from Home Depot or similar. Trim to size with sharp scissors and tape over the exposed buttons. Might not be pretty but it should keep dirt out. Alternatively you might try eBay for a 2nd hand key fob which you would only buy for the case. I think you would need to take out the electronic circuit boards/transponder from your old fob and place into the eBay one. Just a thought - never tried it before. The first one is probably the cheapest and easiest. Or you could apply silicone sealant over the buttons too - just thought of that while I write. Hmmm. Good luck!

    9. My fob failed today I have bought 3 since i bought the car. Anyway I gave your tip a try and brilliant it works Thank you so much

    10. Thanks for this article. Unfortunately, I didn't have the same success you and other commenters had. I tried to cut along the seam as illustrated (btw, is there a seam along the "top" that you cut? Like an "L" shape?). I cut and cut and even tried a dull butter knife to force into the seam I cut and still couldn't peel it away. I was resigned to cutting the small square around my Unlock button (3 sides like a "C"). When I pulled the flap open to investigate I didn't see a plunger. But, when the flap returned to place, the Unlock button was working. Similar to someone else, working to fix it got whatever it is back into place. I wish I could be more descriptive but, again, I don't know what I did to fix it.