ISX CM2250 engine brake help

[Johnh62]

Good morning. I'm a new member here and have a couple questions on an ISX15 engine brake. I'm an independent shop owner and have fairly significant experience with ISX engines, though I'll be the first to admit that I don't know everything!

We have a truck in the shop for a regular customer that there's no perceptible change in engine brake performance between settings 2 and 3(medium and high). All 3 switch positions are indicating normally on Insite. When monitoring VGT desired and actual I'm seeing no immediate change when setting 3 is selected vs 2.

Operationally the engine is running normally with no VGT or EBP codes or symptoms. We are stumped and haven't run across this one in the past. I appreciate any help or guidance I can get!

[Rawze]

Historically, the engine brake ...

setting 1 = 3 cylinders.
setting 2 = 6 cylinders.
setting 3 = 6 cylinders + turbo (up to 28 psi or so) to choke the manifold.

There are variances in this from one engine model to another ... but that is the generalized format.

example: for some engines in setting 2, it will have some turbo use .. some engine models it will not.

some model engines do not even have solenoids, so they use only the turbo itself.

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Is this a de-mandated engine (deleted?).

What are the turbo positions seen during engine brake.. and what is the boost pressures getting to during engine brake on medium, high, low, etc?.

Does the program name in the engine ecu match exactly, what the engine ser# calls for on quickserv.com?.


Has the turbo been replaced at some point?... and is it 100% oem?... and does the part# on it mnatch exactly the part# that the engine ser# calls for?.


last but not least... has anyone bothered to ensure that the exhaust back-pressure sensor is OEM only and not some crappy dorman brand or other garbage someone got from a non official source? .. is it less than 400k miles old? .. and that the circuit/passageway feeding it thru the thermostat housing is not blocked up?. .. and IS the crossover tube from the manifold to the bottom of the thermostat housing leaky?,cracked from heat?. etc?

Anyone done a CAC leak test?... what about pressurizing the whole engine and checking and for air-flow, boost, etc. leaks?.