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pwhittle · 11-17-2025, **(Subject: CM870 Turbo Underspeed and Overspeed )**

Thanks Rawze!

Will do.

Rawze · 03-23-2026, **(Subject: CM870 Turbo Underspeed and Overspeed )**

(11-17-2025 )pwhittle Wrote: Thanks Rawze!

Will do.

just looked at the videos you sent me...

The engine is making full power, no actual power/torque derates, etc.., everything is in order and it is following all data for a non-deleted engine.

However ... boost is a touch low all the time, but not by commands from the ecm. The error is not great enough for a full power/torque derate. etc.. but it is low.

Its a motorhome... I would bet that the CAC is too restrictive (garbage CAC uints are common in motorhomes where engine is mounted in the back of the unit) ... or it very well could be the exhaust is clogging up and getting restrictive ... at least the data points towards this a bit anyways.

That, or the turbo is damaged from carbon stones spitting out of the EGR cooler because it sits too much and carbon and moisture are making carbon stones in the egr cooler,.. then spitting back out every so often, damaging the turbo and weakening it.

.. or perhaps a CAC/boost/egr circuit leak somewhere maybe?.

just my thoughts.

pwhittle · 03-23-2026, **(Subject: CM870 Turbo Underspeed and Overspeed )**

Thanks Rawze,

It has been maxing out at 32 PSI since 2017 when I bought it (2005 model).

I don’t think it is the exhaust. I replaced the factory muffler with an Aero 5050 XL a couple years ago.

Hopefully not the turbo. It could be the CAC or a leak. I’ll keep looking.

Paul

Rawze · 03-24-2026, **(Subject: CM870 Turbo Underspeed and Overspeed )**

(03-23-2026 )pwhittle Wrote: Thanks Rawze,

It has been maxing out at 32 PSI since 2017 when I bought it (2005 model).

I don’t think it is the exhaust. I replaced the factory muffler with an (non-OE replacement) a couple years ago.

Hopefully not the turbo. It could be the CAC or a leak. I’ll keep looking.

Paul

also straight pipe that exhaust and see if boost picks up or codes go away. Your super-super muffler might me part of the issue for all anyone knows.

also,.. you need to see if the program for the engine actually belongs in that engine. Many times, ppl will 'uprate' the power in the engine improperly, and it causes issues like your having due to turbo or other hardware mis-match in the program itself.

What is the program in the ECM that is showing at the window title bar when connectd with Insite?. .. What is the engine ser#?.

pwhittle

Hi Rawze,

ESN 79079781 ECM Code AB10369.22

I am the second owner and I don’t think the previous owner messed with the engine or ECM.

Paul