Ineed some help. I have a 96 dakota with 3.9l and 5 speed. It quit the other day and wouldn't start, towed it home. The next day it started and had P1391 code and a P0121 code. I drove it 40 mile and it was fine. Then the next day drive 30 mile and then it wouldnt start again. Next day it runs with same code. I don't understand what the issues is. I know that its a cam/crank code but if it was one of those sensor's wouldnt it just not run at all?

 

Check for a bad connection or a loose ground? Thatd be the only thing I can think of that would be hit or miss like that.

 

Would that be a ground for the sensor? Where are the other grounds located on the engine block etc?

 

I know there is a splice in the wiring that sometimes gets bad and corroded. iirc its somewhere on the drivers side inner fender.

just do a search and you will find the exact location.