I am at a loss. Replaced lower unit with a new one. Replaced fuel system components from pick p to engine, rebuilt LPFP, HP fuel pump, replaced all fuel filters, replaced plugs, ohmed out coils (good), changed thermostat, temp sensor, flushed motor several times, re-set ECM and STILL get 6 beeps after engine runs WOT for 5 minuets!!!!! Back off throttle and immediately warning horn stops. If I run 15- 20 mins, warning horn - 6 beeps and have to wait to continue at a lower RPM.
Sometimes, when throttle goes to idle after engine is warm, I get 1 long beep and then it no horn. Idle is good. Engine runs fine until warmed up.

I need help!, I,m in offer $3000.00!!!!

have you had a tech hook up the G3 software to read the codes?

No, I have the codes from the maintenance manual. Out of work, so money is tight. 6 beeps relates to three sensors: MAP. TBP and Temp sensor. I checked the temp sensor= good. To get to the MAP sensor you need to disassemble the intake manifold and ECS system. Not up to that yet. But- what does 1 long beep intermittently mean after the throttle goes at idle when engine is hot?

pm sent

Update: I am posting as information for any to use at my expense. Believe me, its expensive- $3600.00 so far.
OK, as refresher- no faults at startup. WOT after about 5 min. of running, 6 beeps, guardian mode enabled. What I did:
1. eliminated the MAP sensor, no change.
2. Reset ECU, replaced thermostat - no change.
3. replaced impeller, no change.
4. Flushed with 50/50 water/muric acid and dawn soap- a bunch of gunk cleaned out. Water temps at 3000-4000 rpm stay below 130. AT WOT, 160 top and bottom.
5. Unplugged temp. sensor after problem surfaced. Motor ran good at WOT.
6. Replaced temp. sensor- problem still there.
7. Rang out temp. sensor harness to ECU= GOOD.
8 WTH !!!!!!!!!
9.Anyone have a diagnostic code reader I could borrow to read the faults????

Found issue- three rubber impeller parts wedged up into vertical water intake tube.

Glad to hear you found the issue.

Thank you. I now can disassemble the motor and reassemble!!