0v just means ground..

There actually is already one circuit like this on the MS board meant for the fast idle control relay. Since we dont really use this feature, it would be pretty simple to jump any output on the processor and have it go to the input resistor on the fast idle circuit, to control a relay, such as the fan control. Just take the fan control output from the processor(you can use x2), and jump that over to the input side of R16(dont keep the input side of R16 soldered in the hole on the board).Now the pin on the DB37 that was designated for fast idle, will now be your fan control, without having to put together any more hardware. Same goes for the fuel pump control relay circuit. The board also has the resistor/transistor for controlling the fuel pump relay, so if you just use the stock ECU for fuel pump control, you would now have 2 circuits already available to drive 2 separate 12volt relays :)

With the Extra code though, you can use led 18 for fan control, and x2 for water injection. Not sure if you need the resistor/transistor circuit if you use led 18 for fan control though, since led 18 already is driven by a transistor...