Since the service, the Montero runs smoother. The transmission also shifts smoother through out the gears, specially going from third to fourth. So I think why the AT light came on was due to the sensor getting wet. At the same thing that this was happening a guy in California put out a message with the same symptoms as mine, wet streets, large puddles of water and heavy rain fall. Well here in the desert, we had some relative hard rains and our street drainage system in not that good.

Anyways I think that the transmission had not been serviced in a while, and thats why the oil came black. The mechanic said it was ok.