Land Rover Repair: leaking intake manifold gasket, obd ii scanner, intake manifold gasket

Question
I just replaced a leaking intake manifold gasket. 3 hours after the installation the service engine light can on. I checked all parts i replaced more than once.
Why am i seeing this light?  

Answer
Without seeing your truck, there's no way to answer that question.  Get an obd ii scanner and see what the code is.  If it's fuel trim, you either have a damaged air meter or a vacuum leak.  That's the most likely.  But you may have swapped some injector and sensor wiring - that's a possibility too.  And of course there are other possible errors - you just have to look really carefully.