Heavy-duty symptoms on this site (DEF and SCR faults, NOx sensors, EGR, DPF, fuel filter restriction, cooling) apply. Per Kenworth and Transport Topics.
Common to all diesels
These apply to PACCAR engines too.
- Hard start when cold
- Cranks, will not start
- White smoke
- Black smoke
- Blue smoke
- Low power / limp mode
- Rough idle
- Water in fuel light
- Fuel in the oil
- Losing coolant
- DPF and regeneration
- Cold-weather gelling
- DEF / SCR faults
- NOx sensor problems
- Clogged EGR valve
- Turbo whistle / boost leak
- Injector knock
- Fuel filter restriction
- Air in the fuel
- Oil consumption
- Crankcase blow-by
- Cavitation / liner pitting
- Maintenance basics
- Winter diesel prep
- Is a DPF/EGR delete legal?
Where this comes from
Last reviewed 2026-10-19. General information only: confirm with your service information and a qualified diesel technician.