496 MAG HO Smartcraft Fault
 

Hello all, great forum here! Hoping some of the more experienced on here can give me some guidance.

My 496 HO with Smartcraft gauges started showing a message on the tach LCD today of "Check Engine". When you hit the MODE button it then cycles to "Sensor Fault". Hitting the MODE button again resets it to show RPM but the little fault icon keeps blinking in the corner.

Warning beeper is working fine (beeps when key is switched on), beeper never sounds, all other readings are normal, engine seems to run fine.

Looking at Merc Manual 33, PCM555 fault codes, it looks like about the only ones that will cycle the Smartcraft warning without a buzzer is a "Main Power Relay" fault, #80 or #81. Anyone have any experience with this?

Trying to avoid buying a Scan tool or Diacom if I don't have to!

Hope everyone had a great Memorial Day!