How to clone a black remote fob .... by eric355

By diyauto
( 3 )

4 minute read

How to clone a black remote fob ....

Compliment of eric355 @


This thread is for all the 355/360/456/550 owners who, like me, for whatever reason have only one black remote fob. Not a very comfortable situation, even with the PIN code. I didn't like the idea to have to turn the key more than 20 times (yes I have at least two "0" in my PIN code :-( ) before starting my car, if i lose my remaining remote. I have even never tried this method !! Don't like neither the cost of a new complete set ...

So, I looked for and found a very cheap alternative. When looking at a black remote circuit (cf picture 1) one can mainly see two chips, the big one is a microcontroler, and the small one is a memory (serial EEPROM).

My guess : the microcontrolers are the same for all remotes and contain the same program, all the genetic (specific) data are contained in the EEPROM. So if I copy the EEPROM content of the functionning remote to the EEPROM of another one (provided it has the same radio frequency : 433 MHz for Europe, 350 MHz for USA) It should work. And guess what? ....... IT WORKS !!!

So here is the procedure:
- you need a EEPROM programmer. Hopefully, it is of a very common type (93C46) and you can find (or even built, see mine in picture 3) very easily a programmer for such memory. Most difficult part to find was a suitable support for Surface Mounted Devices (SMD).Try google and ebay for hardware and freeware ...
- The scary part, you have to unsolder safely the EEPROM from the functionning remote (cf picture 2) .... ouch !! .... Remember it is the only one operative remote ;-) . There are some tips to remove this kind of SMD component.
- Place the EEPROM on the programmer (picture 3), read and save its content (picture 4)
- Remove the EEPROM from the victim remote and program it with the data of operative remote
- Re-solder the EEPROM's

That's all. You have now 2 (or more :-) !!!) identical remotes. Both will work equally. A remote which has not been used for sometimes will just need to be pressed several times in order to resynchronize the alarm ECU.

I thought for some times to a way to read and program data without desoldering the EEPROM, but the only alternative solution is to cut the circuit tracks, solder some wires to the programmer, and then reconnect the tracks ... much more difficult IMO.
The trip to desolder such a SMD component is to remove some solder with an absorbing braid, then, when heating each pin in turn, to slide progressively a razor blade or a feeler gauge between the board and the pins. This avoid the heated pins to resolder on the board. Very efficient.

The programmer i use is there :