2009 Freightliner Columbia intermittent CHECK ENGINE light

I recently bought a 2009 Freightliner Columbia with a Mercedes Benz engine and automated transmission.

While driving it bobtail today, the CHECK ENGINE (or CHECK TRANSMISSION) light would come up intermittently. I am not sure what the light meant, to my embarrassment, in fact two yellow lights would come up simultaneously that look almost identical.

Anyway, during that, the truck would drive just fine and no issues would be noticable to me, not that I know a lot.

In addition, the lights came and went quite often, and frequently coinciding with the truck encountering bumps or rough acceleration in low gear, as if they are associated with shaking.

I tried to read the engine codes when I got to my warehouse, and all I came up was transmission code 25, which means no codes.

Any idea what this might mean. How do I prove or disprove the hypothesis that the wiring harness(es) are to blame?

 

OK, we started with the basics. Antifreeze level was right at the LOW mark. We added antifreeze for the level to be in the middle between LOW and HIGH. That seems to have solved the problem, I took the tractor for a ride and could not reproduce this problem.

I do recall numerous warnings from people and antifreeze level for this Mercedes engine, so we will try very hard to make sure that all fluids are topped up.

But, like all intermittent problems, it is hard to be sure that the problem really went away.