[RussWhite]

I am not alone I see.

I just had my experience with low coolant level alarm. Replaced the sensor and went for a while, and got it again.
Annoying as the level was fine, but coach power got derated about 50% and no cruise. I limped on to my destination.

I started at the sensor end and first remade all the connections on the common side. My final connection to the chassis was above the voltage isolator in the rear electrical cabinet. It's hard to see, but up there. Also redid the grounds on the main battery cables and the one on the rail outside the electrical cabinet. Nothing I found gave me the feeling I had taken care of the root problem.
I had researched the DDEC wiring and knew the connector and pin as well as wire number and color involved. Well, it must have been my lucky day as the only pin with obvious corrosion on the Vehicle Connector ( front side of ECM on the bottom ) was position H3 - low coolant.

A nice wash with contact cleaner on both socket and pin and back together and problem solved. Your mileage as always may vary. Russ