Yes, during a 5v ref failure. What ever sensor the PCM was looking at the time will set the code. It's just luck of the draw which sensor it will be because as far as the PCM is concerned all the circuits that use the 5v ref signal are bad.

^^^^^^ correct and to add to it --- just because the TPS fault code faulted does not mean a darn thing. And most likely, still was good. But one can test for that and even ohm test it out. Actually the TPS was still good because it was mentioned as a changed out to a new TPS. The same goes for crank and cam sensors just cause they faulted means nothing for jist of it. Heck run the boat out of gas and either one of these will fault or both will. Many do not know this and end replacing the sensors because it has faulted and the majority thinking is they must be bad. Not true at all.

Trim position sensor was it. Visiting Mercury tech with same program found it. Thanks all, Expensive to fix but I'm in love with this boat. 2003 27' Fountain.

Thanks for the follow up, digital trim

Thats what mine was also unplugged it and it started right up

Bingo if its a bad sensor / sender.. 30 minutes worth of testing for the sensor / sender end of it. Also there is ohms testing for the sensors as well. This testing is all explained in the service manual.

Thanks all for the great advice. I chose this engine because it had low hours (170) figuring it would be reliable. But like anything complicated and 15 yrs old it is bound to have gremlins. Zoomed around Lake Washington yesterday with my motorcycle heated coat and gloves plugged in. Still smiling the next day. Is there a simple code reader that will help me in the future? Searches here and elsewhere have been confusing.