I am having fault code 125 on Cummins X15 2020 Kenworth T680 after replacing turbo. The issue is happening when pulling loaded truck uphill. Truck boost drops from 30 psi and goes into derate mode. I have tested the hoses, intercooler and turbo for any leaks, didn't find any leaks. I have replaced the intake manifold pressure sensor and the barometric pressure sensor. I am still having the issue. Please Help.
Have you pressure and smoke tested the charge air system? What are the results of the air handling test with Insite?
I did a pressure but not smoke test. Good. Air handling test passed. Was barometric pressure sensor on the wire harness driver side of the engine. Was reading correctly on the code summary. That's why I was getting stumped.
Check IMAP sensor for correct part number per QSOL. I'm guess you already replaced with a new one? Check Exhaust gas pressure sensor for rationality to atmospheric pressure. Biased sensors and plugged pressure tubes are common but usually throw codes related. If your air handing test passes and your 125 still returns Id be getting ahold of Cummins support. Do you have any software revisions that apply?
If the value is in range it won't throw a code. Doesn't mean the value is correct. You should see the value in an insite snapshot and compare to other pressure sensors at key on engine not running. They should all read the same. More or less. One might read ambient and another relative to ambient. Youtube Engine shop Joe has a video.
