Code E-27 is for crankshaft position sensor error......BUT FIRST thing I would do is install a new set of spark plugs,especially if the ones in it have a lot of hours on them and are gapped to wide from wear.....AND DO NOT...I REPEAT!DO NOT use aftermarket spark plugs...us Nissan Part # 22401-FU42A....as you say the truck is running fine this is the FIRST place I would go to is the spark plugs....ALSO change them when the engine is STONE COLD,or you will be putting helicoils in the head as the threads will come out with the plugs.