Very unlikely that it's a pressure sensor or ECT.
On MK5, this is usually a faulty underhood fuse-box. This is how you test it.
Open the hood, and latch the hood latch or un-plug the hood latch connector (so that the vehicle thinks the hood is latched) and arm the vehicle (lock it). Take the cover off the underhood fuse-box, locate fuse SC14 or 15, they should be 10amp fuses. Simply check how much voltage is at the fuse. 2 minutes after the ignition is switched off and the vehicle is locked, there should be 0 volts at these fuses. If you have any voltage at these fuses, the fuse box has to be replaced. Typically you'll see anywhere from 3-5 volts, sometimes even as high as 7-9volts will be present. The corroded fuse box is what is activating the cooling fans to come on.
Sunday, April 7th, 2013 AT 3:16 AM