ECM Check Coolant?

[Keith K]

We're on our first extended trip in our new-to-us 2006 Itasca Ellipse, Freightliner/Cat/Allison. On level or moderate terrain, everything performs fine; however, when climbing a long grade (we're on I-90 in Montana where 6% is common), the check engine light comes on and the Freightliner screen says "ECM Low Coolant". After a few seconds, it disappears, then will reappear on and off until reaching the crest of the grade. It seems to occur when the transmission downshifts into 3rd gear, and on one occasion it seemed to go into the "limp" mode. Once I'm over the hill, everything is OK again. What the heck is "ECM coolant"? I thought the ECM was a computer. Also, don't know if it's related, but the transmission temperature gauge barely moves off the "C" (the weather's been in the 60s-60s). We're at Yellowstone now and wonder if I should worry about this or wait until the trip is over. The transmission fluid checks OK....any ideas? Thanks,
Keith

[Keith K]

We're on our first extended trip in our new-to-us 2006 Itasca Ellipse, Freightliner/Cat/Allison. On level or moderate terrain, everything performs fine; however, when climbing a long grade (we're on I-90 in Montana where 6% is common), the check engine light comes on and the Freightliner screen says "ECM Low Coolant". After a few seconds, it disappears, then will reappear on and off until reaching the crest of the grade. It seems to occur when the transmission downshifts into 3rd gear, and on one occasion it seemed to go into the "limp" mode. Once I'm over the hill, everything is OK again. What the heck is "ECM coolant"? I thought the ECM was a computer. Also, don't know if it's related, but the transmission temperature gauge barely moves off the "C" (the weather's been in the 60s-60s). We're at Yellowstone now and wonder if I should worry about this or wait until the trip is over. The transmission fluid checks OK....any ideas? Thanks,
Keith

[GaryKD]

Hi Keith,
My suggestion is cheap and simple to try. If it works, great.

Check the coolant level in the overflow tank. Do not use the sight glass. Get a rod of some kind and put it in the tank to see where the coolant level really is. If you find it is below the sight glass, add the amount of coolant necessary to get the level at least back to the sight glass.

[Keith K]

Thanks Gary - I assumed that the only "ECM" belonged to the Allison Transmission......maybe there's one for the engine side also. A low tank on a grade could expose a sensor - I'll give it a try!

[Gary RVRoamer]

The ECM is the Engine Control Module, i.e. engine computer. Freightliner mounted radiator coolant sensors are notorious for giving false low coolant readings on grades and a Low Cooolant signal will display as a "Check Engine" condition. Exactly how that shows up depends on the specific dashboard display and Driver Info Center configured on your chassis, so there may be some variation.

I'm adding a link to the Freightliner forum, since this problem has nothing to do with Allison.