Baffling problem with a '97 Cummins M11

Sounds like a low boost condition that could be caused by a few different things.
Bad injector
Plugged air filter
Fuel line restriction or sucking air into the fuel system
Standpipe in fuel tank getting blocked by debris in the tank
Valve clearance issue when engine is warmed up
Boost leak in CAC or boots and piping
Is this a dead cyl on one hole or just an overall power loss?

 

Ok, so the ecm is deratting causing the power loss. Need the code # and description and follow the trouble tree to success.

 

Is this from your truck diagnostic display or reading the ecm with a computer with cummins Insite?

 

Ok, the diagnostic display is in SAE format which is different than what engine manufacturers use. To follow the diagnostic procedures for your Cummins engine you need to connect to Cummins insite. This will give you a different trouble code and the corresponding troubleshooting procedure for that particular code.
Or you could continue guessing at the problem and spend lots more money than you already have until you hit the fault.
What indicated to you that the problem was the boost sensor and/or turbo? Do you have explanation material for the diagnostic display codes and what they mean?
If I was to guess at it, I would say you have a boost leak and when the ecm sees high rpm and engine load it senses low boost pressure for those conditions and derates, killing your power level, but at the same time saving your engine from damage.

 

SAE fault 102 - 2 for a M11 is for the intake manifold pressure circuit. The Cummins fault code number is 433. SAE codes get mis-read all the time. Like Bender said the actual code should be retrieved using Insite to get the actual Cummins code. I also don't like the code description it is telling you and that may be leading you astray. If it is 433, this means the ECM is reading boost pressure that is higher than it thinks is physically possible given the current engine operating characteristics. The ECM will only log this code at idle. When the ECM logs this code it will derate to the "No air" setting, or basically no or low boost. There is not thing wrong with your turbo, or air to air. Your boost gauge is only a mechanical gauge reading actual manifold pressure. Your boost is low because the ECM is cutting back power until the 433 code becomes inactive. This is usually an electrical problem with intake manifold pressure sensor or related wiring. You said you replaced the sensor in the turbo. This makes no sense as there are no sensors in the turbos. The intake manifold pressure sensor is located at the back of the intake manifold. It should be a 3 wire sensor. Is this the sensor you are talking about? Your truck is 15 years old, the engine wiring could also be the problem. Wiring gets brittle over time, rubs through, and shorts out. You also need to thoroughly inspect the wiring and the terminals inside the connectors for any bend or worn pins. Also look for corrosion. All these will send false signals. The intake pressure sensor is supplied with 5 volts, and a return circuit that is also shared by the oil pressure sensor, ambient air pressure sensor and the coolant level sensor. If any of these other sensors are shorting out it could also be causing this problem and not necessarily causing a fault of their own.