...I purchased a new ‘empty’ fob from eBay for approximately $3.00, including post. It did have a blank blade, but I wasn’t interested in that. All I needed (at the time) was the case and the silver button that popped out the blade. I took my blade and circuit board and put them into the new fob, and until I washed my fob a month or so ago, I have had a working remote control fob/key.
It is probably still worthwhile posting the board pics so here goes.
That is essentially what I have done. In my case the remote access was not operating due to a board fault which occurred without being immersed. The low resistance shunt across the battery on my board is probably related to the 433MHz transmitter section. Removing the battery to prevent it going flat does not affect the function of the RFID chip.
I suspect that the unintended immersion of your fob has also damaged the 433MHz transmitter on the board because it is powered from the battery at all times just waiting for a key press. Such treatment can cause major faults to the active devices due to the interconnection of all pins via the conducting medium of the water causing excessive currents to be injected into points which were never intended to endure such currents. The RFID chip on the board has escaped damage because it is not powered by the battery and drying the fob has allowed this chip to remain functional. Therefore you can still start the car.
It is just a guess but it may be possible for a low voltage powered up board to escape damage if the battery is submerged before the components on the board get wet due to the resistive shunt across the battery causing the voltage to be lowered to a point where excessive currents can't be sustained. I have seen the catastrophic effects resulting from mice setting up home in a 2kW sine wave inverter and urinating on the heatsink mounting the high voltage switching mosfets. The mosfets were sure to fail due to excessive currents but in failing they in turn produced a domino effect on 20 or more low powered devices on the control board.
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