2015 Kw t680 cummins isx fault codes

2554, exhaust gas pressure sensor data erratic. Check the sensor connector for corrosion.
3714, engine protection derate condition detected. Probably caused by the 2554 code.

 

Top right corner of engine, near egr cross over pipe. Should be plumbed in the front exhaust manifold section. 3 wire sensor.

 

The little steel tube that runs from the exhaust manifold into the block integrated into the thermostat housing supplies the sensor. Exhaust Gas Pressure sensor is the one threaded vertically into the housing directly above the tube inlet. You also need to verify this tube is NOT plugged with soot.
To unplug the sensor before removal, slide the lock (little red tab) sideways, then it's a push and hold the lock clip and remove. It gets hot so you usually have to wiggle and fidget to get it to come off. When replacing the sensor I recommend silver anti-seize on the threads, and Vaseline on the electrical connector, you'll thank me later.
The life expectancy of these, as well as the IMAP (Intake Manifold Air Pressure sensor located in the intake manifold) is approx 250k miles for reliable feedback. Don't clean them, change them.

Number 4 in the image (image is a CM871, but the sensor location is the same through the CM2350)