My 496 HO is cutting out at idle while in gear and does not occur when idling in the neutral position. The motor will cut out randomly while idling in gear, the tach with drop to zero then pick right back up to normal idle speed. It's a split second that this occurs. Also there is a single random beep at idle in gear but does not happen the same time as the cutting out of the motor. Once I am out of the idle RPM range it's fine and doesn't happen while normal running, Also I noticed occasionally when I come off plane and pull back into neutral I get a single beep.

Thanks for any input leading to the solution of this issue...

EVERY sensor shows a fault ??? what voltage is reporting here when running and is voltage reading steady thru out all rpms including idle ? All power connections tight and CLEAN and NO corrosion 100 percent --- is your battery cable properly size ?

The times I have seen were EVERY sensor is faulted is when a MEFI 3 scan tool is used for MEFI 4 and so on --- or the/ ECM / PCM has issues with internal power and grounds or shorted J connections or bad .

What Scan tool are U using and what version ??

I would start with alternator, battery, and connections. Doesn't sound like you have enough power to run the electronics.

EVERY sensor shows a fault ??? what voltage is reporting here when running and is voltage reading steady thru out all rpms including idle ? All power connections tight and CLEAN and NO corrosion 100 percent --- is your battery cable properly size ?

I have not had the opportunity to run the boat yet and ready the voltage. I will be doing that this weekend. All Cables are properly sized as well as the batteries and all connections are clean and tight, I checked that stuff once this problem started.

The times I have seen were EVERY sensor is faulted is when a MEFI 3 scan tool is used for MEFI 4 and so on --- or the/ ECM / PCM has issues with internal power and grounds or shorted J connections or bad .

What Scan tool are U using and what version ??

I am using a Rinda Techmate Pro Marine Scan tool which is qualified to talk to PCM-555. I have had this exact tool connected to his motor before to read the hours and I have never had it log these fault codes.

Where you able to resolve the issue Kalugs22 and if so what was the root cause? I'm experiencing same with my 496 ho's and as previously recommended above I have gone through/cleaned all connections/grounds without luck and switched batteries around. I've noticed it gets worse with heat/humidity and only occurs at idle, never while cruising down the lake and only after warmed up for a while. Never during warm-up or leaving marina, always seems to surface later in the day. Scanner will pickup crank position sensor fault but something else is driving the single beep/tach fluctuation (i did replace the sensor when symptoms started last year). I did have a trim check low on one side which I disconnected the trim sensor last weekend and it didn't show up, but it was cooler in Illinois. Volts for battery and 5 volt are strong when it does beep... i need to take pictures of the freeze frame data before leaving to analyze further.

I believe my issue is the smart craft trim sensor. When the problems originally occurred my boat had been in the water for 2 days so anytime i started it up it would do it immediately. The boat sat in dry storage all week and when i cleared the codes and put it in on saturday it was fine, it sat in the water overnight and on sunday i was able to get it to act up while idling under load. I had no beeps but when i put the scan tool on it the only new code i had was "trim ckt lo". I disconnected it and everything seemed to be ok so i ordered a new one. This would make some sense since it took sitting in the water for a time period before it would act up giving water a chance to penetrate the sensor causing a short. My buddies boat with a 496 had an issue last year where it wouldn't start and the cause was the trim sensor. Did you unplug your trim sensor where it comes through the transom behind the motor?

yes, I did disconnect the plug on the back transom. That is good to hear (see) because it's been driving me nuts! Thanks for posting back :-).