Technical Fiat Marea Week. - Remote Control in Key

[MartinekM]

Hi,
the remote control electronic in my blue keys has stopped working. I tried to change batteries but it didn't help. So I re-soldered all contacts. The LED diode is not flashing when the button is pressed, nevertheless the LED is working when I power it up directly from the voltage supply. Also I tried to measure all electronic parts and I found out that possible problem could be a crystal oscillator which provides a clock rate for a microchip PIC 16CR83. This crystal doesn't supply any clock rate, according to the osciloscop. Is there any experienced guy with measuring equipment who could measure the crystal in the working key and write here a frequency which the crystal is supplying?


Thanks
Martin

 

[bulldog5046]

would this not be specific to the car?

 

[Venters]

would this not be specific to the car?

Wouldn't have thought so. They will be a generic unit so that you can programme new keys.


I have working keys but no osciloscope or knowledge of how to use one.

 

[bulldog5046]

the crystal is what defines the channel on the frequency, so surely this needs to be unique otherswise you would unlock all marea's with 1 key.

 

[Venters]

No the code that is transmitted would be uniqe and the frequency its trasmitted on would all be the same surely.

 

[jug]

all will use the same frequency, it is only the modulated data that is different. which is why you can replace the crystal if needs be. the only part you really cant replace is the microcontroller. it sends a stream of bits to the key's RF transmitter, containing among other things the rolling code. each microcontroller will have a different set of codes, which are paired (identicle) to the microcontoller in the reciever. as long as you have a matching pair, and both are at the same point in the rolling code sequence, then it will work.

so MartinekM would be able take the crystal from another marea or bravo or brava remote, and fit it to the faulty key.

although i dont think thats the problem, i know from experience that the LED will still illuminate even if the crystal is dead or removed.

 

[MartinekM]

all will use the same frequency, it is only the modulated data that is different. which is why you can replace the crystal if needs be. the only part you really cant replace is the microcontroller. it sends a stream of bits to the key's RF transmitter, containing among other things the rolling code. each microcontroller will have a different set of codes, which are paired (identicle) to the microcontoller in the reciever. as long as you have a matching pair, and both are at the same point in the rolling code sequence, then it will work.

so MartinekM would be able take the crystal from another marea or bravo or brava remote, and fit it to the faulty key.

although i dont think thats the problem, i know from experience that the LED will still illuminate even if the crystal is dead or removed.

Regarding your last sentence, if the LED will still illuminate even if the crystal is dead or removed...then, it is not my case...the LED doesn't work either. So here is the question what is driving the LED. if the LED is driven by microcontroller then that's bad. But If the LED is driven by transistor then this one could be replaced. But these are only assumptions. The electrical scheme of the key electronics would be more helpful. Isn't it somewhere on the internet?

And what is the frequency of the crystal?

 

[jug]

what is driving the LED.

The electrical scheme of the key electronics would be more helpful. Isn't it somewhere on the internet?

And what is the frequency of the crystal?

i dont know exactly what makes the LED illuminate, and i dont have any diagrams to show how a key works, but i do know that when i removed the crystal on a key the LED still illuminated.

i dont know what frequency the crystal transmits at, but i do know that fitting the crystal from another key worked fine.

the problem i then had was the broken key had been used more then 256 times before i fixed it, meaning it was no longer synchronised with the reciever. i dont know how to reset everything back to the start of the rolling code sequence so now i'm stuck. i suggest you fix your key before you press the button 256 times.