CrankCase Pressure SPN 101 FMI 15 FC 1974

[Hermjeji]

So Following up with this:

1. Know that engine is close to life here with 18k hours at 750K km of heavy duty driving (laoded at 54-63k kgs). Replaced the cranckase filter with the new magic filter. Haven't really had the issue again. Code came up once on a big pull on a hill but just flashed on and off.

INSERT NEW PROBLEM:

2. Real pain in the ass code keeps coming up 3362, FC 1682, DEF dosing unit input line. Steps taken with assistance of a mechanic friend:
- Fuel actuator valve was faulty, replaced it
- code went away (luck?)
- Code came back, checked lines, no kinks or damage
- DEF filter replaced 2 months ago
- DEF dosing unit replaced

Code still comes on. Now after 1 week of it running fine with replaced dosing unit. Not sure what next steps here are, could it be some type of air in the system that needs to be purged?