I had that come up on my car a few times, the first time the garage said the computer can set it off when the vehicle when it reaches a certain mileage. They serviced it all and didn't have the computer tool to turn it off so it wasn't until they took it to another garage up the road they managed to reset the computer and get rid of the light.

The other time something in the engine was being funny I think the cam belt or something and it didn't get up the hill so it was obviously faulty.