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dhirocz · 11-05-2026, **(Subject: Cm871 Jake solenoids inop )**

Engine brake solenoids suddenly quit on me.
The engine still builds boost to Jake… but neither solenoid comes on.
The engine was properly demandated and both the solenoids and the harness were replaced with new Cummins parts close to 300k miles ago when I inframed it.

Since both solenoids quit working at the same time, but I’m still getting boost, I am going to assume that I have an electrical issue, most likely under the valve cover. Is there any hidden relays or fuses that I need to be aware of I should also be checking for while I have things apart?

Rawze · 11-06-2026, **(Subject: Cm871 Jake solenoids inop )**

does it show they are on in insite when they are supposed to be active?.

dhirocz · 11-06-2026, **(Subject: Cm871 Jake solenoids inop )**

I’ll try to get them to come on today when I go to check over things.
What would cause the ecm to not command them on, but still build boost to Jake?

dhirocz · 11-07-2026, **(Subject: Cm871 Jake solenoids inop )**

Looks like they are supposed to be active…pulling the valve cover today to take a look.

Rawze · 11-07-2026, **(Subject: Cm871 Jake solenoids inop )**

(11-07-2026 )dhirocz Wrote: Looks like they are supposed to be active…pulling the valve cover today to take a look.

could be an oil pressure issue on the top end?.

If the crank case filter is clogging up (excessive crank case pressures), it will make the top end starve of oil.

dhirocz · 11-07-2026, **(Subject: Cm871 Jake solenoids inop )**

I can check, but I doubt it. It was demandated over 500k ago, still runs a bypass filter, has the oil pump mod and makes good pressure… the rockers were all blown clean of any residues.

So far I see nothing obvious under the valve cover so I’m going to pull out my dvom and start checking circuits.

dhirocz · 11-07-2026, **(Subject: Cm871 Jake solenoids inop )**

The Jake harness ohms out fine, but I noticed the pins were hardly sticking out at all. I wonder that is the issue… I was able to pull them out of the engine side a good 1/4”. Before they were almost flush… so I will be reassembling to retest.

dhirocz

Just posting to say that was the issue. I don’t know why the pins were set so shallow in the Jake harness, but pulling them out of the connector to 1/4” did the trick. I also made a point to squeeze the connectors a bit tighter before pushing them back onto the solenoids. Took it over monteagle today without issue.