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A friend's car key was not working properly, and he took it to an electronics repair shop. They quoted a very high price for the repair and my friend refused and got his key back.

Now he brought me the key and asked me to fix it, but before me the crafty person removed some of the components of the switch from the PCB.

This is the switch board. You can still see some components soldered there, but I have no clue.

enter image description here

If I search for the PCB number in Google, the same boards appear there. However, I don't have enough experience to determine what these components are and what their values are. Can you help me find these three components?

enter image description here

Here are some links to other images:

Full resulation

24-pins component:

datasheet

Another full resulation image:

image

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    \$\begingroup\$ Some form of resistor for 2 and 3, and a capacitor for 1. There is no way of knowing what value they are without measuring them in isolation or finding a schematic. \$\endgroup\$
    – Tom Carpenter
    Sep 3, 2020 at 16:47
  • \$\begingroup\$ "crafty person"... if you look, there is still some fillets so they were probably knocked off \$\endgroup\$
    – user16222
    Sep 3, 2020 at 16:53
  • \$\begingroup\$ They look like parts for the matching network for the PCB antenna. It will not be easy to find the values. \$\endgroup\$
    – Spehro Pefhany
    Sep 3, 2020 at 17:04
  • \$\begingroup\$ Even if you knew what types of components would need to be there and you would put them there, in my opinion you still have a very high chance that the key still would not work. Almost all "intelligence" is inside the chip. Either that chip needs to be re-programmed (maybe that's not even possible) or replaced (and then it needs to be programmed as well). My guess is that the chance that you can repair this is zero. Your friend will have to bite the bullet and pay dearly for a new card probably from the car dealer. \$\endgroup\$
    – Bimpelrekkie
    Sep 3, 2020 at 19:22

1 Answer 1

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They seem to be connected to the antenna connection (pins 23 and 24); looking at the datasheet, my best guess would be that 1 is a capacitor between V and ground, 2 is an inductor, and 3 is an antenna.

Have a look for yourself to see if that is correct; it shouldn't be all that difficult to reverse-engineer looking at figure 7-3 on page 9 of the datasheet.

The values I can't tell, but they probably used the suggestions in the datasheet.

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  • \$\begingroup\$ I think "3" is another inductor and the antenna ist the pcb track going in a loop around everything \$\endgroup\$
    – Jens
    Jul 19, 2022 at 21:39

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