Engine Management Light

I have just recently removed the EGR Valve on my Freelander 1 TD4 and cleaned it up and then took it out for a spin there was alack of power and black smoke coming out of the exhaust. On looking inside I found one of the hoses had come away from its fitting. So I refitted it and then started the engine. This time the engine management light came on and it will not rev properly. I assume this is a safety measure to stop engine damage. I have checked all the hose fittings and the EGR is properly fitted etc but the light won't go out and the engine won't rev properly. It was slightly drizzly when I refitted the EGR so is it possible that water has got into a sensor which is shorting the connection or is it something serious?

Can the management light be reset without going to a specialist?

Any help would be greatly appreciated.

Cheers
RD

Ok just taken the freelancer out for a spin and the light has gone out and I have power back again.

Further to this thread, the reason i removed the EGR was because I noticed a small amount of oil around the area of the engine cover by the EGR. I can hear wind rush around that area when I accelerate and thought it might have been a split hose. I have checked all the hoses and they are fine so i am not too sure where it is coming from. Is there a flange or gasket that might have split. I am not losing water or oil and there is no white smoke so I can safely assume its not ahead gasket problem.

Does anybody have any ideas?

I will try to get a picture up if i can.

Oh and there are some spatters of oil around the area too.

Here is a picture of where the oil seems to be most obvious.