Alarms and s.l.o.w mode

[jgrauel]

Recently had 5.0gXi replaced with 5.7L on 2005 Crownline 240EX. Everything is brand new on this engine. Well, it has been two months of trial and error with the shop. Starter issues, overheating, batteries dying, and now when all seems to run well we get a mysterious alarm and the engine goes into slow mode.
Last week we replaced the new thermostat with another new one and this week we get the alarms and slow mode. Gauges read 150-160 temps, oil pressure is ~40. Any ideas where we should go and will the ECM give a code? I have a video of the behavior, but will not load here.

 

[alldodge]

Welcome
The motors need to be scanned. With slow mode (guardian) and the alarm there will be a code.

Mentioned going from a 5.0 to 5.7 GXI, is the 5.7 using the 5.0 ECM?

 

[jgrauel]

Yes, the mechanic says they are the same.

 

[alldodge]

Yes, the mechanic says they are the same.

Then you need another Mechanic

 

[Horigan]

SLOW mode uses independent temp and oil pressure switches from the gauge sensor data. The issue is likely one of those switches, or the wiring to them. Agree that a scan will point you in the right direction.

 

[jgrauel]

Turns out the wire on one of the exhaust sensors was burned and appears to be the culprit. However, I am also replacing the exhaust sensors and the temp sensor just to be safe.
Thank you.