In a nutshell, I have spent $7500 in the last 3 months troubleshooting my 2014 6.7L.
The initial codes were P000f (fuel system over pressure, relief valve activated) and P0254 (Fuel injection pump valve current too high).
Being 1200 miles from home, I took the truck to a highly recommended and reputable shop without doing more than checking fuses, grounds, and obvious damage.
The shop replaced the FRP sensor and the fuel pressure control solenoid on the CP3.
No changes and a $1500 bill.
Fast forward, 3 other shops, several thousand dollars, no changes. I changed the PCM, no difference.
By this time other symptoms had developed, coolant temp sensor, intake air temperature, and water in fuel were reading intermittently or not at all.
Assuming a wiring issue may not be obvious to the naked eye (and getting desperate) I ordered a new engine bay wiring harness.
The original was quite brittle and tattered, but while removing it I still didn’t notice anything catastrophic.
Installed the new harness and everything is working perfectly.
Upon a closer inspection of the original harness, the wires, tape, and looming all around the turbo were melted.
These are difficult to inspect on the truck as they are buried in a cluster of better protected lines, and also without removing the intake and fender-well they are quite hidden.
Hopefully I can save someone some serious headaches and $$$$$$ if they are as unlucky as myself with such random symptoms.
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