2009 Kenworth Odometer Issue (CM871 to CM570 Engine Swap)

So I just bought a 2009 KW W900 that originally had a CM871 ISX but one of the previous owners had swapped in an earlier CM570 ISX manufactured in 2002 into the truck. Everything seems to work (gauges, switches, etc.) with the exception of the odometer reading. The digital display seems to be working but instead of numbers it just reads dashes "------". This is with the truck on or running. If the truck is off it will display a figure over a million miles but it doesn't seem to count up, it just stays at that same number. Any ideas?