1992 f-150 gauge cluster swap

I just swapped my cluster without tach to a 92 cluster with tach. it is supposed to be a plug and play swap out! with new cluster installed the check engine light comes on after driving for a few minutes and resets when you shut it off. Any suggestions why this is happening? if I re install the original cluster the check engine will not illuminate (bulb is good).
Any ideas would be greatly appreciated:banghead: