What's notable isn't that moisture intrusion exists (it's been around as long as diesel electronics), but how often the same failure pattern is now surfacing on trucks past the 700k-mile mark:

• Repeated ECM swaps that don't resolve the underlying fault
• Harness replacements followed by the same codes weeks later
• Sensor-by-sensor replacement with no clear root cause
• Rubber seals on harness connectors degrading and wicking water down the wires themselves

Several electricians have described tearing into trucks where two ECMs, two harnesses, and a full sensor sweep still didn't kill the fault. The common thread: there's no systematic, guided workflow for environmental intrusion diagnostics on heavy-duty platforms. Shotgun parts swapping is filling the gap, and it's expensive.

Expect to see more discussion this year around connector-level diagnostics, dielectric grease practices, and aftermarket sealing kits for aging Cascadia fleets. If you're running a DD15 past warranty, this is the failure mode worth getting ahead of.