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Key Fob Not Working


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Hi all,

I have all three keys for my TS, but the second key fob doesn't work. It was like this when I purchased the car. I've changed the Battery previously and the red LED doesn't light up on any key press. It all looks clean inside but something is obviously wrong. Anyone had the same symptoms before and if so what was the fix and how much did it cost?

Thanks!

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Hi all,

I have all three keys for my TS, but the second key fob doesn't work. It was like this when I purchased the car. I've changed the battery previously and the red LED doesn't light up on any key press. It all looks clean inside but something is obviously wrong. Anyone had the same symptoms before and if so what was the fix and how much did it cost?

Thanks!

Inside the key fob there is a contact that touches the Battery may have been bent and not contacting the Battery properly, If it is try bending it back up a little.

It may be a long shot but worth a try.

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Thanks, I've had a bit of a go at that previously with no success - think I'll take another look though.

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OK, I haven't taken it apart too far, but here's some shots. You'll have to excuse the dirt/dust! In the third shot on the connector at the back on the right you can see a small area that looks like corrosion, however I don't believe this is stopping contact. Let me know if the images are useful, thanks.

01.JPG

03.JPG02.JPG

04.JPG

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Hard to spot corrosion in a piccy...

Use a cotton bud with a trace of WD40 on it to clean the Battery contacts.

Can you see in the picture where the Battery contact also connects to the PCB (printed circuit board) via that gold flashed "print". Thats's another potential (:)) problem. You might be able to slip a piece of thin paper moistened with WD under it to clean it.

If non of this works, you are going to have to dismantle further to look for corrosion damage. Any white/green deposits around any of the electronic components spells trouble.

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I agree, a further strip down will be required.

I have just stripped mine down to the circuit board and if you cant see any corosion you may want to look at getting a new key.

There is nothing that really could be wrong.

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Thanks both. I've cleaned it as suggested but unfortunately still no joy. I took the buttons out from the top size so could also give a bit of a clean on that side. What's the recommendation for taking the key apart any further or any other thoughts?

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Hi Eddie, thanks - I already have a new Battery that I have tested in my working key and I also have the old Battery from it which also has some power. Neither are working in it unfortunately.

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Thanks. Got it all apart and cleaned, still no good. Here's a shot - look similar to yours? Is the glue present and the black mark - not sure if these should be of concern.

05.JPG

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Just a thought take the working one apart and look to see if there is any visable difference, might see something to give a clue as to what the problem is.

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put the Battery in and check the board has power, 1 end of the multimeter on the ground and the other on a side of the switch, you should have 3v

I originally thought it was a switch but you've got 2 so the chances of both of them faffing up are small. Bridge the switch with a bit of wire and see if the light comes on.

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Running out of options with this.

You have nothing to loose now, as it's not repairable as such by Toyota.

First you have to be very sure in your own mind that the two Battery contacts are OK and that they connect to the PCB OK.

Another check is with a multimeter set on a low ohms range. Check that the switches actually close when pressed... measure from end to end contacts as you press. Make sure there is no Battery in the key.

Next... using a small brush and some foam cleaner etc or detergent carefully wash, then rinse thoughly the whole circuit board. It won't hurt it. Dry as best you can with paper trying to "wick" all moisture from the switches and under the black IC etc (The bit with many legs on) then place on a radiator or in hot sun for several hours to dry. Don't exceed about 50 degrees C.... it's not the components you'll harm, it's any plastic.

Fit the Battery, try again... if it works, great, but remove the Battery again and leave for a lot longer to be sure it's dry, if no good remove Battery and leave again in hot place for several more hours and try again.

On more trick you can try with the Battery removed. Wrap and squeeze the PCB in some tin foil to short out all electrical points. Sometimes logic parts get "stuck or locked" in an indeterminate state and residual charge prevents the microprocessor reseting.

If all that sounds mad, I am an electronics tech and that technique has been used 100's of times on everything from remotes to complete pieces of equipment.

Good luck :)

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Just a thought take the working one apart and look to see if there is any visable difference, might see something to give a clue as to what the problem is.

Thanks Eddie. I might give in a shot after trying a couple of the points below....

put the battery in and check the board has power, 1 end of the multimeter on the ground and the other on a side of the switch, you should have 3v

I originally thought it was a switch but you've got 2 so the chances of both of them faffing up are small. Bridge the switch with a bit of wire and see if the light comes on.

Cheers nrgizer. I'm in the process of trying to source a multimeter.

Running out of options with this.

Another check is with a multimeter set on a low ohms range. Check that the switches actually close when pressed... measure from end to end contacts as you press. Make sure there is no battery in the key.

Thanks Mooly. I will try this and associated advice when I get the multimeter.

On more trick you can try with the battery removed. Wrap and squeeze the PCB in some tin foil to short out all electrical points. Sometimes logic parts get "stuck or locked" in an indeterminate state and residual charge prevents the microprocessor reseting.

I have foil and am happy with an off the wall approach :thumbsup: I'll give it a go.

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Well all is not lost... be methodical, try as nrgizerbunny say to see if you can pick up 3 volts on the PCB. That really is the golden rule... check the power supplies are present and correct.

Electronic parts are supremely reliable, usually the cause of a fault is either physical... damage, poor connection etc, or some slight corrosion caused by moisture. The 3 volts from the Battery is enough to cause "electrolysis" between different metals... any white or greenish deposits are a giveaway for that.

I know washing the whole caboodle sounds really extreme... I have done that to dozens of TV chassis, remotes, etc with liquid damage, and with perfect results as long as parts themselves are not corroded. It's an unofficial technique that works well.

Look at the key closely with a bright light, check for cracks in the PCB too.

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Thanks both. I decided to go ahead and take apart my working key fob to compare it to. A couple of shots below. It answered a couple of questions for me:

1.) The white "blob" that I thought may have been glue wasn't meant to be there...looks like it was a small piece of broken plastic from the case, I have removed it but it didn't resolve the problem.

2.) The black mark on the board (toward top right) is normal.

The comparison in general makes the non-functioning PCB look a lot more "worn"....e.g. look at the main chip on the bottom left, you can't read all of the text on it. Also the LED itself looks a bit worse as do some of the circuits on the back. I have no idea of the history of the key, e.g. whether it was dropped in liquid or similar.

Any other clues from the shots below?

On the left the non-functioning unit, functioning one on the right....

06.JPG

07.JPG

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immobiilzer is on a prox sensor so is powered when it goes near the keyhole. It doesn't need a Battery.

if you've got power, i suspect one of the inductors is blown. its very unusual for a chip to fail, its more likely its a passive component or a dodgy connection.

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The broken plastic... could it be from dissasembling... or could it have been trodden on etc in the past.

Bottom left picture... the dark discoloration on the gold flashed print... is that traces of possible liquid damage... does it scrape off with a finger.

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Thanks again both.

Bottom left picture... the dark discoloration on the gold flashed print... is that traces of possible liquid damage... does it scrape off with a finger.

No it doesn't. I tried very lightly with a flat head screw driver also, but this didn't seem to work either.

Is the main chip on the board the one "unique" piece? E.g. I was wondering if that could be moved to a new board, not sure.

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Where would you get a new one from...

Yes you can remove SMD (surface mount parts) but it's fairly specialised to do it without damaging the print. The IC wouldn't be my first suspect... unless as you say the key has "history" we don't know about. Whatever the fault "it's never the chip" as a rule :)

http://www.diyaudio.com/forums/parts/127924-working-smd-how-do-without-specialised-tools.html

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