Bad ECM?
 

Recently bought an '08 Xd with 99K on the clock. Top end was super loud but ran ok. CEL came on often. Codes were for the oil control valve and cam sensor. Eventually ran a carfax and found the mileage had been turned back at 189k!
I had no idea you could roll back digital odometers...anyway, mechanics at multiple shops reset the code and checked the OCV. Found that there was an oil pressure issue. Replaced OCV and that only made the codes go away for like 50 miles.
Convinced the car lot I got it from to refund me $1500 and found a used motor with 125k on the clock from LKQ. Had the motor swapped and all was well. after about 400 miles the CEL light popped up again with the same codes. The car runs great, quiet and smooth and getting 30+ mpg. tried disconnecting the battery and connected a 1 ohm 10 watt resistor across the positive and negative cables. Codes cleared but came back on in 48 miles. I am also unable to reset the maintenance light that tells you to change the oil. No matter what I or the mechanics tried it won't go off. Beginning to think that the person who set the odometer back possibly f'ed up the ECM and that those codes are ghosts. I saw the thread here about doing a reset by pulling the EFI fuse. However, that fuse seems like it is part of a relay? Impossible to get the fuse out without pulling that whole piece from what I can tell. First question, has anyone tried that reset on an XD? Second question, used ECMs are out there, should I make a swap? Could that hurt?
Thanks,

Nathan