Series 60 Coolant Level Fault

This week on the Series 60 we had a Coolant Level Low fault to fix. This code was set last week when we tried to get it running after refilling it with the coolant we drained. The system uses a coolant level sensor in the fill tank on top of the radiator.

Active fault code for Coolant Level set by the ECM, as shown on the scan tool.

Our first task after retrieving the code off the ECM was to refer to Detroit Diesel's Power Service Literature to find out what exactly this code means and what procedures are recommended for troubleshooting.

Looking up service literature for this fault code.

Detroit Diesel recommends ensuring that coolant level is actually correct first.

Coolant fill tank on top of radiator, with coolant level sensor right above the radiator fan.

What we found after taking the pressure cap off was the coolant was indeed low. It took almost 2 gallons to fill it up to the correct level where we could see it in the tank with a flashlight.

No more coolant fault code.

The service literature says that following this procedure, the fault code should no longer be set. Of course, we cleared the rest of the codes manually, but there was no active fault for coolant level after we put the scan tool back on the truck.

My reflection:

It's not always a bad sensor or faulty wiring that can set a fault or cause a problem. Sometimes it's the simplest solution that is the correct one. So here our first question for a "coolant level low" fault on a truck should be, "does it actually have enough coolant in it?" And our first action should be to check that it does.

Sometimes it's best not to overthink things and keep it simple.