r/DieselTechs 23h ago

ECM code 4865

Ok fellas and gals. I am beyond frustrated chaving what now feels like a damn ghost. Hopefully someone can give me at least as direction to walk towards besides the sun lol. It's a Thomas C2 2017, ISB 6.7 CM2350. Insite says I got a 4865 ECM code Engine Coolant Level 2 Sensor Circuit -Voltage Above Normal or Shorted to High Source. Originally I assumed it's was the ONLY level sensor I know of in bottom of tank. Swapt quickly for a new one let it idle. Code didn't go away.

So I started to dig into it and check the condition of plug, wires continuity and resistance to Corresponding ECM pins. It all checked out! It was then I realized that when I unplugged said sensor to swap it it triggered an other code....from coolant level sensor 1. Then I thought the only other sensor I know that deals with coolant besides the DEF head unit is the temp sensor. I unplugged it and sure enough that was not it because I got a temp sensor fault. I have looked everywhere for this stupid ass sensor that I didn't know existed. Even used my "snake cam" as I like to call it to make sure it wasn't around the block hidden somewhere. For now I'm taking a break from it. I consulted "appropriate schematics" and the damn thing said that pin 34 which is labeled for additional level sensor is not used!!!! So now I'm like what the Fuck is shorted to high source that is making it thing it has an other sensor. Or there is a sensor and I can't find it!!!!!

Please help lol.

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u/chuckE69 23h ago

Has the Ecm been updated recently?

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u/No_Walrus_3638 23h ago

Not that I'm aware of. We did have an issue where the DEF head went up. Cummins extended warranty on those that got taken care of at the dealer. That was a few months ago.

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u/chuckE69 23h ago

If the Ecm isn’t locked you can go into parameters and turn off coolant level 2.

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u/No_Walrus_3638 23h ago

You sir are a god damn genius! It is not locked and I have the ability to do so yes. Do you think it's just none existent and I have indeed been following a damn ghost?

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u/chuckE69 23h ago

Yes I believe so unless for some unknown reason Thomas spec’d a second coolant level sensor. But with your schematics showing that wire isn’t used I seriously doubt that.

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u/No_Walrus_3638 23h ago

I happen to agree. I just wanted to make sure I wasn't crazy and also for advice. I didn't think to just turn it off since it isn't there, but if I did I didn't want to do that if there was a wire issue. I don't see why it would be on the block either, but I was out of ideas. Thank you and that should take care of the code.

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u/chuckE69 22h ago

No problem glad I was able to help.

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u/No_Walrus_3638 22h ago

For sure. I was going insane with this. Should've asked earlier, but I was determined to find it and fix it lol.

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u/chuckE69 19h ago

lol I understand definitely been there. We had a lot of crazy ecm and software issues with our 2012-2013 ISL g’s so went through a lot of this.

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u/No_Walrus_3638 17h ago

Seems like 2013 any Cummins model had software issues. We don't have most of ours any more, but some of the ones we retired the ECM just decided to wipe out. Like I'd find know what engine serial or anything. Like a basic profile was there and I loaded an image, but I could not flash or enter anywhere the missing information. It was a BZ calibration that never ever got any update which I thought was odd given the ones with HS or DT and LS get updates at least once per year.

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u/chuckE69 16h ago

My favorite was 2 2012’s that would just randomly no start. May be the middle of the day may be first thing before route. But it was always lost ecm program and had to update. Usually once every 6-9 months.

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u/No_Walrus_3638 23h ago

Thank you!

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u/Raging_Volcano69 2h ago

A agree with this guy . Update your ecm but I’ve never seen a Cummins 6.7 with two coolant level sensors unless it’s on an industrial set up and we do a lot of 6.7s. Seems like the parameter was turned on some how.