Originally Posted by ColinW
Theory/
As an electronic engineer, I would say you have a better than 50/50 chance of getting it to work again.
By itself, water is not the problem. Unfortunately, the contaminated water, which will be electrolytic, gets onto the printed circuit board, and because the power is on, behaves as if there are many short circuits all across the circuit board. In a few cases this can cause catastropic failure. However, it can just cause the programme to go mad, thus disabling the car.
Remedy/
Dissonnect battery & remove the ECU module. I do not know if this is possible, but try and extract the ECU printed circuit board, ie the board with all the Chips on. Try not to touch the board except by the connector, as electrostatic discharge from yourself can destroy the IC's.
It is worth just having a look on the board for evidence of salt deposits. These need be not that obvious, but you can see sort of water marks, particulary where the water has been.
Now you will have to wash the board, initialy with warm tap water, and a soft brush, pay particular attention to the watermarked areas.
DO NOT BE AFRAID ABOUT THE WATER. BOARDS ARE CLEANED IN THE FACTORY USING WATER AND QUITE AGRESSIVE CLEANERS TO REMOVE SOLDERING FLUXES..
The next step is the most important. You now have to rinse the board with a good quality de-ionised water. Do this several times in fresh de-i .
Shake off as much of the water as you can. Do not be tempted to blow it off with your breath . You can blow it off with a good quality electronic airduster aerosol, that is used for computers etc
Now you must dry it thoroughly. A fan oven set to 50- deg C. Make sure the oven is at temp before you put it in. Leave for about 1/2 hr, or longer if you have the time.
Now at this point it is important, that you put it back in the case ASAP, having previously wash & dried the case as well.
Now what I don't know, and I'm sure somebody will, if the ECU needs some form of reset after putting it back. Batteries are disconnected routinely, so it should start working again.
NOW. If it works again, it is worth taking the ECU out once more, and coating the printed circuit board with a protective lacquer. This is routinely done in aerospace and militatry electronics for this very reason. Even condensed water droplets cause havoc with modern electrtonics.
Hope this helps, you have nothing to lose.
Good luck
Colin
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